[v8,3/6] firmware: psci: Read and use vendor reset types

SoC vendors have different types of resets and are controlled through
various registers. For instance, Qualcomm chipsets can reboot to a
"download mode" that allows a RAM dump to be collected. Another example
is they also support writing a cookie that can be read by bootloader
during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these
vendor reset types to be implemented without requiring drivers for every
register/cookie.

Add support in PSCI to statically map reboot mode commands from
userspace to a vendor reset and cookie value using the device tree.

A separate initcall is needed to parse the devicetree, instead of using
psci_dt_init because mm isn't sufficiently set up to allocate memory.

Reboot mode framework is close but doesn't quite fit with the
design and requirements for PSCI SYSTEM_RESET2. Some of these issues can
be solved but doesn't seem reasonable in sum:
 1. reboot mode registers against the reboot_notifier_list, which is too
    early to call SYSTEM_RESET2. PSCI would need to remember the reset
    type from the reboot-mode framework callback and use it
    psci_sys_reset.
 2. reboot mode assumes only one cookie/parameter is described in the
    device tree. SYSTEM_RESET2 uses 2: one for the type and one for
    cookie.
 3. psci cpuidle driver already registers a driver against the
    arm,psci-1.0 compatible. Refactoring would be needed to have both a
    cpuidle and reboot-mode driver.

Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
 drivers/firmware/psci/psci.c | 104 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)

On Thu, Nov 07, 2024 at 03:38:27PM -0800, Elliot Berman wrote:
> SoC vendors have different types of resets and are controlled through
> various registers. For instance, Qualcomm chipsets can reboot to a
> "download mode" that allows a RAM dump to be collected. Another example
> is they also support writing a cookie that can be read by bootloader
> during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these
> vendor reset types to be implemented without requiring drivers for every
> register/cookie.
> 
> Add support in PSCI to statically map reboot mode commands from
> userspace to a vendor reset and cookie value using the device tree.
> 
> A separate initcall is needed to parse the devicetree, instead of using
> psci_dt_init because mm isn't sufficiently set up to allocate memory.

Nit: information below this point is more a cover letter than for the
commit log.

> Reboot mode framework is close but doesn't quite fit with the
> design and requirements for PSCI SYSTEM_RESET2. Some of these issues can
> be solved but doesn't seem reasonable in sum:
>  1. reboot mode registers against the reboot_notifier_list, which is too
>     early to call SYSTEM_RESET2. PSCI would need to remember the reset
>     type from the reboot-mode framework callback and use it
>     psci_sys_reset.
>  2. reboot mode assumes only one cookie/parameter is described in the
>     device tree. SYSTEM_RESET2 uses 2: one for the type and one for
>     cookie.
>  3. psci cpuidle driver already registers a driver against the
>     arm,psci-1.0 compatible. Refactoring would be needed to have both a
>     cpuidle and reboot-mode driver.
> 
> Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> ---
>  drivers/firmware/psci/psci.c | 104 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 104 insertions(+)
> 
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 2328ca58bba61fdb677ac20a1a7447882cd0cf22..e60e3f8749c5a6732c51d23a2c1f453361132d9a 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -79,6 +79,14 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
>  static u32 psci_cpu_suspend_feature;
>  static bool psci_system_reset2_supported;
>  
> +struct psci_reset_param {
> +	const char *mode;
> +	u32 reset_type;
> +	u32 cookie;
> +};
> +static struct psci_reset_param *psci_reset_params __ro_after_init;
> +static size_t num_psci_reset_params __ro_after_init;
> +
>  static inline bool psci_has_ext_power_state(void)
>  {
>  	return psci_cpu_suspend_feature &
> @@ -305,9 +313,38 @@ static int get_set_conduit_method(const struct device_node *np)
>  	return 0;
>  }
>  
> +static void psci_vendor_system_reset2(const char *cmd)
> +{
> +	unsigned long ret;
> +	size_t i;
> +
> +	for (i = 0; i < num_psci_reset_params; i++) {
> +		if (!strcmp(psci_reset_params[i].mode, cmd)) {
> +			ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> +					     psci_reset_params[i].reset_type,
> +					     psci_reset_params[i].cookie, 0);
> +			/*
> +			 * if vendor reset fails, log it and fall back to
> +			 * architecture reset types
> +			 */
> +			pr_err("failed to perform reset \"%s\": %ld\n", cmd,
> +			       (long)ret);
> +			return;
> +		}
> +	}
> +}
> +
>  static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
>  			  void *data)
>  {
> +	/*
> +	 * try to do the vendor system_reset2
> +	 * If the reset fails or there wasn't a match on the command,
> +	 * fall back to architectural resets
> +	 */
> +	if (data && num_psci_reset_params)
> +		psci_vendor_system_reset2(data);
> +
>  	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
>  	    psci_system_reset2_supported) {

This is a mess. To issue architectural warm reset we check reboot_mode,
for vendor resets we ignore it - there is no rationale, that's the point
I am making.

Also see my question on the other thread re: user space and reset
"modes".

I appreciate we are not making progress but I don't want to pick up
the pieces later after merging this code - it is unclear to me what's
the best path forward - I would like to understand how other
platforms/arches behave in this respect.

>  		/*
> @@ -750,6 +787,73 @@ static const struct of_device_id psci_of_match[] __initconst = {
>  	{},
>  };
>  
> +#define REBOOT_PREFIX "mode-"
> +
> +static int __init psci_init_system_reset2_modes(void)
> +{
> +	const size_t len = strlen(REBOOT_PREFIX);
> +	struct psci_reset_param *param;
> +	struct device_node *psci_np __free(device_node) = NULL;
> +	struct device_node *np __free(device_node) = NULL;
> +	struct property *prop;
> +	size_t count = 0;
> +	u32 magic[2];
> +	int num;
> +
> +	if (!psci_system_reset2_supported)
> +		return 0;
> +
> +	psci_np = of_find_matching_node(NULL, psci_of_match);
> +	if (!psci_np)
> +		return 0;
> +
> +	np = of_find_node_by_name(psci_np, "reset-types");
> +	if (!np)
> +		return 0;
> +
> +	for_each_property_of_node(np, prop) {
> +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> +			continue;
> +		num = of_property_count_u32_elems(np, prop->name);
> +		if (num != 1 && num != 2)
> +			continue;
> +
> +		count++;
> +	}
> +
> +	param = psci_reset_params =
> +		kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL);
> +	if (!psci_reset_params)
> +		return -ENOMEM;
> +
> +	for_each_property_of_node(np, prop) {
> +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> +			continue;
> +
> +		param->mode = kstrdup_const(prop->name + len, GFP_KERNEL);

FWIW - I think you need to keep the logic in the previous loop into account
because that's what is used to allocate param, it is not a given that
param is valid at this stage if I am not mistaken - the previous loop
checked:

	num = of_property_count_u32_elems(np, prop->name);
	if (num != 1 && num != 2)
		continue;

Lorenzo

> +		if (!param->mode)
> +			continue;
> +
> +		num = of_property_read_variable_u32_array(np, prop->name, magic,
> +							  1, ARRAY_SIZE(magic));
> +		if (num < 0) {
> +			pr_warn("Failed to parse vendor reboot mode %s\n",
> +				param->mode);
> +			kfree_const(param->mode);
> +			continue;
> +		}
> +
> +		/* Force reset type to be in vendor space */
> +		param->reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic[0];
> +		param->cookie = num > 1 ? magic[1] : 0;
> +		param++;
> +		num_psci_reset_params++;
> +	}
> +
> +	return 0;
> +}
> +arch_initcall(psci_init_system_reset2_modes);
> +
>  int __init psci_dt_init(void)
>  {
>  	struct device_node *np;
> 
> -- 
> 2.34.1
>

On Fri, Nov 15, 2024 at 02:51:16PM +0100, Lorenzo Pieralisi wrote:
> On Thu, Nov 07, 2024 at 03:38:27PM -0800, Elliot Berman wrote:
> > SoC vendors have different types of resets and are controlled through
> > various registers. For instance, Qualcomm chipsets can reboot to a
> > "download mode" that allows a RAM dump to be collected. Another example
> > is they also support writing a cookie that can be read by bootloader
> > during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these
> > vendor reset types to be implemented without requiring drivers for every
> > register/cookie.
> > 
> > Add support in PSCI to statically map reboot mode commands from
> > userspace to a vendor reset and cookie value using the device tree.
> > 
> > A separate initcall is needed to parse the devicetree, instead of using
> > psci_dt_init because mm isn't sufficiently set up to allocate memory.
> 
> Nit: information below this point is more a cover letter than for the
> commit log.
> 
> > Reboot mode framework is close but doesn't quite fit with the
> > design and requirements for PSCI SYSTEM_RESET2. Some of these issues can
> > be solved but doesn't seem reasonable in sum:
> >  1. reboot mode registers against the reboot_notifier_list, which is too
> >     early to call SYSTEM_RESET2. PSCI would need to remember the reset
> >     type from the reboot-mode framework callback and use it
> >     psci_sys_reset.
> >  2. reboot mode assumes only one cookie/parameter is described in the
> >     device tree. SYSTEM_RESET2 uses 2: one for the type and one for
> >     cookie.
> >  3. psci cpuidle driver already registers a driver against the
> >     arm,psci-1.0 compatible. Refactoring would be needed to have both a
> >     cpuidle and reboot-mode driver.
> > 
> > Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
> > Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> > ---
> >  drivers/firmware/psci/psci.c | 104 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 104 insertions(+)
> > 
> > diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> > index 2328ca58bba61fdb677ac20a1a7447882cd0cf22..e60e3f8749c5a6732c51d23a2c1f453361132d9a 100644
> > --- a/drivers/firmware/psci/psci.c
> > +++ b/drivers/firmware/psci/psci.c
> > @@ -79,6 +79,14 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
> >  static u32 psci_cpu_suspend_feature;
> >  static bool psci_system_reset2_supported;
> >  
> > +struct psci_reset_param {
> > +	const char *mode;
> > +	u32 reset_type;
> > +	u32 cookie;
> > +};
> > +static struct psci_reset_param *psci_reset_params __ro_after_init;
> > +static size_t num_psci_reset_params __ro_after_init;
> > +
> >  static inline bool psci_has_ext_power_state(void)
> >  {
> >  	return psci_cpu_suspend_feature &
> > @@ -305,9 +313,38 @@ static int get_set_conduit_method(const struct device_node *np)
> >  	return 0;
> >  }
> >  
> > +static void psci_vendor_system_reset2(const char *cmd)
> > +{
> > +	unsigned long ret;
> > +	size_t i;
> > +
> > +	for (i = 0; i < num_psci_reset_params; i++) {
> > +		if (!strcmp(psci_reset_params[i].mode, cmd)) {
> > +			ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> > +					     psci_reset_params[i].reset_type,
> > +					     psci_reset_params[i].cookie, 0);
> > +			/*
> > +			 * if vendor reset fails, log it and fall back to
> > +			 * architecture reset types
> > +			 */
> > +			pr_err("failed to perform reset \"%s\": %ld\n", cmd,
> > +			       (long)ret);
> > +			return;
> > +		}
> > +	}
> > +}
> > +
> >  static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> >  			  void *data)
> >  {
> > +	/*
> > +	 * try to do the vendor system_reset2
> > +	 * If the reset fails or there wasn't a match on the command,
> > +	 * fall back to architectural resets
> > +	 */
> > +	if (data && num_psci_reset_params)
> > +		psci_vendor_system_reset2(data);
> > +
> >  	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> >  	    psci_system_reset2_supported) {
> 
> This is a mess. To issue architectural warm reset we check reboot_mode,
> for vendor resets we ignore it - there is no rationale, that's the point
> I am making.

If I expand the comment to:


 * try todo the vendor system_reset2
 * If the reset fails or there wasn't a match on the command,
 * fall back to architectural resets.
 * Ignore reboot_mode enum to behave like setting a cookie, which don't
 * care about the reboot_mode.


Help to address this concern?

> 
> Also see my question on the other thread re: user space and reset
> "modes".
> 
> I appreciate we are not making progress but I don't want to pick up
> the pieces later after merging this code - it is unclear to me what's
> the best path forward - I would like to understand how other
> platforms/arches behave in this respect.
> 

I went through the couple hundred drivers which register reboot and
restart handlers. The majority don't care about reboot command nor
reboot_mode enum. The few that do:

Two drivers which I could find which care about the reboot command don't
look at the reboot_mode argument.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/efi/efibc.c?h=v6.11#n35
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/power/reset/reboot-mode.c?h=v6.11#n42

One driver looks at the reboot command overrides the reboot_mode
argument:

[3]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/watchdog/pnx4008_wdt.c?h=v6.11#n125

I wasn't able to find any platform/arches which check the reboot_mode
before reading the reboot command.

> >  		/*
> > @@ -750,6 +787,73 @@ static const struct of_device_id psci_of_match[] __initconst = {
> >  	{},
> >  };
> >  
> > +#define REBOOT_PREFIX "mode-"
> > +
> > +static int __init psci_init_system_reset2_modes(void)
> > +{
> > +	const size_t len = strlen(REBOOT_PREFIX);
> > +	struct psci_reset_param *param;
> > +	struct device_node *psci_np __free(device_node) = NULL;
> > +	struct device_node *np __free(device_node) = NULL;
> > +	struct property *prop;
> > +	size_t count = 0;
> > +	u32 magic[2];
> > +	int num;
> > +
> > +	if (!psci_system_reset2_supported)
> > +		return 0;
> > +
> > +	psci_np = of_find_matching_node(NULL, psci_of_match);
> > +	if (!psci_np)
> > +		return 0;
> > +
> > +	np = of_find_node_by_name(psci_np, "reset-types");
> > +	if (!np)
> > +		return 0;
> > +
> > +	for_each_property_of_node(np, prop) {
> > +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> > +			continue;
> > +		num = of_property_count_u32_elems(np, prop->name);
> > +		if (num != 1 && num != 2)
> > +			continue;
> > +
> > +		count++;
> > +	}
> > +
> > +	param = psci_reset_params =
> > +		kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL);
> > +	if (!psci_reset_params)
> > +		return -ENOMEM;
> > +
> > +	for_each_property_of_node(np, prop) {
> > +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> > +			continue;
> > +
> > +		param->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
> 
> FWIW - I think you need to keep the logic in the previous loop into account
> because that's what is used to allocate param, it is not a given that
> param is valid at this stage if I am not mistaken - the previous loop
> checked:
> 
> 	num = of_property_count_u32_elems(np, prop->name);
> 	if (num != 1 && num != 2)
> 		continue;

of_property_read_variable_u32_array() performs effectively the same
check.  It returns -EOVERFLOW if it couldn't find enough (== 0) or too
many values (>2). I currently have the added bonus of complaining in
dmesg about the bad reboot mode property, instead of silently ignoring.

- Elliot

> > +		if (!param->mode)
> > +			continue;
> > +
> > +		num = of_property_read_variable_u32_array(np, prop->name, magic,
> > +							  1, ARRAY_SIZE(magic));
> > +		if (num < 0) {
> > +			pr_warn("Failed to parse vendor reboot mode %s\n",
> > +				param->mode);
> > +			kfree_const(param->mode);
> > +			continue;
> > +		}
> > +
> > +		/* Force reset type to be in vendor space */
> > +		param->reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic[0];
> > +		param->cookie = num > 1 ? magic[1] : 0;
> > +		param++;
> > +		num_psci_reset_params++;
> > +	}
> > +
> > +	return 0;
> > +}
> > +arch_initcall(psci_init_system_reset2_modes);
> > +
> >  int __init psci_dt_init(void)
> >  {
> >  	struct device_node *np;
> > 
> > -- 
> > 2.34.1
> >

On Fri, Nov 15, 2024 at 11:08:13AM -0800, Elliot Berman wrote:
> On Fri, Nov 15, 2024 at 02:51:16PM +0100, Lorenzo Pieralisi wrote:
> > On Thu, Nov 07, 2024 at 03:38:27PM -0800, Elliot Berman wrote:
> > > SoC vendors have different types of resets and are controlled through
> > > various registers. For instance, Qualcomm chipsets can reboot to a
> > > "download mode" that allows a RAM dump to be collected. Another example
> > > is they also support writing a cookie that can be read by bootloader
> > > during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these
> > > vendor reset types to be implemented without requiring drivers for every
> > > register/cookie.
> > > 
> > > Add support in PSCI to statically map reboot mode commands from
> > > userspace to a vendor reset and cookie value using the device tree.
> > > 
> > > A separate initcall is needed to parse the devicetree, instead of using
> > > psci_dt_init because mm isn't sufficiently set up to allocate memory.
> > 
> > Nit: information below this point is more a cover letter than for the
> > commit log.
> > 
> > > Reboot mode framework is close but doesn't quite fit with the
> > > design and requirements for PSCI SYSTEM_RESET2. Some of these issues can
> > > be solved but doesn't seem reasonable in sum:
> > >  1. reboot mode registers against the reboot_notifier_list, which is too
> > >     early to call SYSTEM_RESET2. PSCI would need to remember the reset
> > >     type from the reboot-mode framework callback and use it
> > >     psci_sys_reset.
> > >  2. reboot mode assumes only one cookie/parameter is described in the
> > >     device tree. SYSTEM_RESET2 uses 2: one for the type and one for
> > >     cookie.
> > >  3. psci cpuidle driver already registers a driver against the
> > >     arm,psci-1.0 compatible. Refactoring would be needed to have both a
> > >     cpuidle and reboot-mode driver.
> > > 
> > > Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
> > > Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> > > ---
> > >  drivers/firmware/psci/psci.c | 104 +++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 104 insertions(+)
> > > 
> > > diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> > > index 2328ca58bba61fdb677ac20a1a7447882cd0cf22..e60e3f8749c5a6732c51d23a2c1f453361132d9a 100644
> > > --- a/drivers/firmware/psci/psci.c
> > > +++ b/drivers/firmware/psci/psci.c
> > > @@ -79,6 +79,14 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
> > >  static u32 psci_cpu_suspend_feature;
> > >  static bool psci_system_reset2_supported;
> > >  
> > > +struct psci_reset_param {
> > > +	const char *mode;
> > > +	u32 reset_type;
> > > +	u32 cookie;
> > > +};
> > > +static struct psci_reset_param *psci_reset_params __ro_after_init;
> > > +static size_t num_psci_reset_params __ro_after_init;
> > > +
> > >  static inline bool psci_has_ext_power_state(void)
> > >  {
> > >  	return psci_cpu_suspend_feature &
> > > @@ -305,9 +313,38 @@ static int get_set_conduit_method(const struct device_node *np)
> > >  	return 0;
> > >  }
> > >  
> > > +static void psci_vendor_system_reset2(const char *cmd)
> > > +{
> > > +	unsigned long ret;
> > > +	size_t i;
> > > +
> > > +	for (i = 0; i < num_psci_reset_params; i++) {
> > > +		if (!strcmp(psci_reset_params[i].mode, cmd)) {
> > > +			ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> > > +					     psci_reset_params[i].reset_type,
> > > +					     psci_reset_params[i].cookie, 0);
> > > +			/*
> > > +			 * if vendor reset fails, log it and fall back to
> > > +			 * architecture reset types
> > > +			 */
> > > +			pr_err("failed to perform reset \"%s\": %ld\n", cmd,
> > > +			       (long)ret);
> > > +			return;
> > > +		}
> > > +	}
> > > +}
> > > +
> > >  static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> > >  			  void *data)
> > >  {
> > > +	/*
> > > +	 * try to do the vendor system_reset2
> > > +	 * If the reset fails or there wasn't a match on the command,
> > > +	 * fall back to architectural resets
> > > +	 */
> > > +	if (data && num_psci_reset_params)
> > > +		psci_vendor_system_reset2(data);
> > > +
> > >  	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> > >  	    psci_system_reset2_supported) {
> > 
> > This is a mess. To issue architectural warm reset we check reboot_mode,
> > for vendor resets we ignore it - there is no rationale, that's the point
> > I am making.
> 
> If I expand the comment to:
> 
> 
>  * try todo the vendor system_reset2
>  * If the reset fails or there wasn't a match on the command,
>  * fall back to architectural resets.
>  * Ignore reboot_mode enum to behave like setting a cookie, which don't
>  * care about the reboot_mode.

/*
 * Check if the system supports vendor resets and issue
 * SYSTEM_RESET2 if the reboot command matches a vendor reset.
 * Ignore reboot_mode and execute SYSTEM_RESET2 with type and
 * cookie as defined by the firmware bindings.
 *
 * If the reset fails or there is not a match for the command
 * fall back to architectural resets; reset type detection in
 * this case will be done using reboot_mode.
 */

?

> Help to address this concern?

Not entirely, sorry, I will get back to this.

> > Also see my question on the other thread re: user space and reset
> > "modes".
> > 
> > I appreciate we are not making progress but I don't want to pick up
> > the pieces later after merging this code - it is unclear to me what's
> > the best path forward - I would like to understand how other
> > platforms/arches behave in this respect.
> > 
> 
> I went through the couple hundred drivers which register reboot and
> restart handlers. The majority don't care about reboot command nor
> reboot_mode enum. The few that do:
> 
> Two drivers which I could find which care about the reboot command don't
> look at the reboot_mode argument.
> 
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/efi/efibc.c?h=v6.11#n35
> [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/power/reset/reboot-mode.c?h=v6.11#n42
> 
> One driver looks at the reboot command overrides the reboot_mode
> argument:
> 
> [3]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/watchdog/pnx4008_wdt.c?h=v6.11#n125

Thanks for doing that, that helps.

> I wasn't able to find any platform/arches which check the reboot_mode
> before reading the reboot command.
> 
> > >  		/*
> > > @@ -750,6 +787,73 @@ static const struct of_device_id psci_of_match[] __initconst = {
> > >  	{},
> > >  };
> > >  
> > > +#define REBOOT_PREFIX "mode-"
> > > +
> > > +static int __init psci_init_system_reset2_modes(void)
> > > +{
> > > +	const size_t len = strlen(REBOOT_PREFIX);
> > > +	struct psci_reset_param *param;
> > > +	struct device_node *psci_np __free(device_node) = NULL;
> > > +	struct device_node *np __free(device_node) = NULL;
> > > +	struct property *prop;
> > > +	size_t count = 0;
> > > +	u32 magic[2];
> > > +	int num;
> > > +
> > > +	if (!psci_system_reset2_supported)
> > > +		return 0;
> > > +
> > > +	psci_np = of_find_matching_node(NULL, psci_of_match);
> > > +	if (!psci_np)
> > > +		return 0;
> > > +
> > > +	np = of_find_node_by_name(psci_np, "reset-types");
> > > +	if (!np)
> > > +		return 0;
> > > +
> > > +	for_each_property_of_node(np, prop) {
> > > +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> > > +			continue;
> > > +		num = of_property_count_u32_elems(np, prop->name);
> > > +		if (num != 1 && num != 2)
> > > +			continue;
> > > +
> > > +		count++;
> > > +	}
> > > +
> > > +	param = psci_reset_params =
> > > +		kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL);
> > > +	if (!psci_reset_params)
> > > +		return -ENOMEM;
> > > +
> > > +	for_each_property_of_node(np, prop) {
> > > +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> > > +			continue;
> > > +
> > > +		param->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
> > 
> > FWIW - I think you need to keep the logic in the previous loop into account
> > because that's what is used to allocate param, it is not a given that
> > param is valid at this stage if I am not mistaken - the previous loop
> > checked:
> > 
> > 	num = of_property_count_u32_elems(np, prop->name);
> > 	if (num != 1 && num != 2)
> > 		continue;
> 
> of_property_read_variable_u32_array() performs effectively the same
> check.  It returns -EOVERFLOW if it couldn't find enough (== 0) or too
> many values (>2). I currently have the added bonus of complaining in
> dmesg about the bad reboot mode property, instead of silently ignoring.

Right but we are dereferencing param (param->mode) before carrying out that
check.

Thanks,
Lorenzo

> 
> - Elliot
> 
> > > +		if (!param->mode)
> > > +			continue;
> > > +
> > > +		num = of_property_read_variable_u32_array(np, prop->name, magic,
> > > +							  1, ARRAY_SIZE(magic));
> > > +		if (num < 0) {
> > > +			pr_warn("Failed to parse vendor reboot mode %s\n",
> > > +				param->mode);
> > > +			kfree_const(param->mode);
> > > +			continue;
> > > +		}
> > > +
> > > +		/* Force reset type to be in vendor space */
> > > +		param->reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic[0];
> > > +		param->cookie = num > 1 ? magic[1] : 0;
> > > +		param++;
> > > +		num_psci_reset_params++;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +arch_initcall(psci_init_system_reset2_modes);
> > > +
> > >  int __init psci_dt_init(void)
> > >  {
> > >  	struct device_node *np;
> > > 
> > > -- 
> > > 2.34.1
> > >

On Mon, Nov 18, 2024 at 01:26:48PM +0100, Lorenzo Pieralisi wrote:
> On Fri, Nov 15, 2024 at 11:08:13AM -0800, Elliot Berman wrote:
> > On Fri, Nov 15, 2024 at 02:51:16PM +0100, Lorenzo Pieralisi wrote:
> > > On Thu, Nov 07, 2024 at 03:38:27PM -0800, Elliot Berman wrote:
> > > > SoC vendors have different types of resets and are controlled through
> > > > various registers. For instance, Qualcomm chipsets can reboot to a
> > > > "download mode" that allows a RAM dump to be collected. Another example
> > > > is they also support writing a cookie that can be read by bootloader
> > > > during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these
> > > > vendor reset types to be implemented without requiring drivers for every
> > > > register/cookie.
> > > > 
> > > > Add support in PSCI to statically map reboot mode commands from
> > > > userspace to a vendor reset and cookie value using the device tree.
> > > > 
> > > > A separate initcall is needed to parse the devicetree, instead of using
> > > > psci_dt_init because mm isn't sufficiently set up to allocate memory.
> > > 
> > > Nit: information below this point is more a cover letter than for the
> > > commit log.
> > > 
> > > > Reboot mode framework is close but doesn't quite fit with the
> > > > design and requirements for PSCI SYSTEM_RESET2. Some of these issues can
> > > > be solved but doesn't seem reasonable in sum:
> > > >  1. reboot mode registers against the reboot_notifier_list, which is too
> > > >     early to call SYSTEM_RESET2. PSCI would need to remember the reset
> > > >     type from the reboot-mode framework callback and use it
> > > >     psci_sys_reset.
> > > >  2. reboot mode assumes only one cookie/parameter is described in the
> > > >     device tree. SYSTEM_RESET2 uses 2: one for the type and one for
> > > >     cookie.
> > > >  3. psci cpuidle driver already registers a driver against the
> > > >     arm,psci-1.0 compatible. Refactoring would be needed to have both a
> > > >     cpuidle and reboot-mode driver.
> > > > 
> > > > Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
> > > > Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> > > > ---
> > > >  drivers/firmware/psci/psci.c | 104 +++++++++++++++++++++++++++++++++++++++++++
> > > >  1 file changed, 104 insertions(+)
> > > > 
> > > > diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> > > > index 2328ca58bba61fdb677ac20a1a7447882cd0cf22..e60e3f8749c5a6732c51d23a2c1f453361132d9a 100644
> > > > --- a/drivers/firmware/psci/psci.c
> > > > +++ b/drivers/firmware/psci/psci.c
> > > > @@ -79,6 +79,14 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
> > > >  static u32 psci_cpu_suspend_feature;
> > > >  static bool psci_system_reset2_supported;
> > > >  
> > > > +struct psci_reset_param {
> > > > +	const char *mode;
> > > > +	u32 reset_type;
> > > > +	u32 cookie;
> > > > +};
> > > > +static struct psci_reset_param *psci_reset_params __ro_after_init;
> > > > +static size_t num_psci_reset_params __ro_after_init;
> > > > +
> > > >  static inline bool psci_has_ext_power_state(void)
> > > >  {
> > > >  	return psci_cpu_suspend_feature &
> > > > @@ -305,9 +313,38 @@ static int get_set_conduit_method(const struct device_node *np)
> > > >  	return 0;
> > > >  }
> > > >  
> > > > +static void psci_vendor_system_reset2(const char *cmd)
> > > > +{
> > > > +	unsigned long ret;
> > > > +	size_t i;
> > > > +
> > > > +	for (i = 0; i < num_psci_reset_params; i++) {
> > > > +		if (!strcmp(psci_reset_params[i].mode, cmd)) {
> > > > +			ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> > > > +					     psci_reset_params[i].reset_type,
> > > > +					     psci_reset_params[i].cookie, 0);
> > > > +			/*
> > > > +			 * if vendor reset fails, log it and fall back to
> > > > +			 * architecture reset types
> > > > +			 */
> > > > +			pr_err("failed to perform reset \"%s\": %ld\n", cmd,
> > > > +			       (long)ret);
> > > > +			return;
> > > > +		}
> > > > +	}
> > > > +}
> > > > +
> > > >  static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> > > >  			  void *data)
> > > >  {
> > > > +	/*
> > > > +	 * try to do the vendor system_reset2
> > > > +	 * If the reset fails or there wasn't a match on the command,
> > > > +	 * fall back to architectural resets
> > > > +	 */
> > > > +	if (data && num_psci_reset_params)
> > > > +		psci_vendor_system_reset2(data);
> > > > +
> > > >  	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> > > >  	    psci_system_reset2_supported) {
> > > 
> > > This is a mess. To issue architectural warm reset we check reboot_mode,
> > > for vendor resets we ignore it - there is no rationale, that's the point
> > > I am making.
> > 
> > If I expand the comment to:
> > 
> > 
> >  * try todo the vendor system_reset2
> >  * If the reset fails or there wasn't a match on the command,
> >  * fall back to architectural resets.
> >  * Ignore reboot_mode enum to behave like setting a cookie, which don't
> >  * care about the reboot_mode.
> 
> /*
>  * Check if the system supports vendor resets and issue
>  * SYSTEM_RESET2 if the reboot command matches a vendor reset.
>  * Ignore reboot_mode and execute SYSTEM_RESET2 with type and
>  * cookie as defined by the firmware bindings.
>  *
>  * If the reset fails or there is not a match for the command
>  * fall back to architectural resets; reset type detection in
>  * this case will be done using reboot_mode.
>  */
> 
> ?
> 
> > Help to address this concern?
> 
> Not entirely, sorry, I will get back to this.
> 
> > > Also see my question on the other thread re: user space and reset
> > > "modes".
> > > 
> > > I appreciate we are not making progress but I don't want to pick up
> > > the pieces later after merging this code - it is unclear to me what's
> > > the best path forward - I would like to understand how other
> > > platforms/arches behave in this respect.
> > > 
> > 
> > I went through the couple hundred drivers which register reboot and
> > restart handlers. The majority don't care about reboot command nor
> > reboot_mode enum. The few that do:
> > 
> > Two drivers which I could find which care about the reboot command don't
> > look at the reboot_mode argument.
> > 
> > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/efi/efibc.c?h=v6.11#n35
> > [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/power/reset/reboot-mode.c?h=v6.11#n42
> > 
> > One driver looks at the reboot command overrides the reboot_mode
> > argument:
> > 
> > [3]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/watchdog/pnx4008_wdt.c?h=v6.11#n125
> 
> Thanks for doing that, that helps.
> 
> > I wasn't able to find any platform/arches which check the reboot_mode
> > before reading the reboot command.
> > 
> > > >  		/*
> > > > @@ -750,6 +787,73 @@ static const struct of_device_id psci_of_match[] __initconst = {
> > > >  	{},
> > > >  };
> > > >  
> > > > +#define REBOOT_PREFIX "mode-"
> > > > +
> > > > +static int __init psci_init_system_reset2_modes(void)
> > > > +{
> > > > +	const size_t len = strlen(REBOOT_PREFIX);
> > > > +	struct psci_reset_param *param;
> > > > +	struct device_node *psci_np __free(device_node) = NULL;
> > > > +	struct device_node *np __free(device_node) = NULL;
> > > > +	struct property *prop;
> > > > +	size_t count = 0;
> > > > +	u32 magic[2];
> > > > +	int num;
> > > > +
> > > > +	if (!psci_system_reset2_supported)
> > > > +		return 0;
> > > > +
> > > > +	psci_np = of_find_matching_node(NULL, psci_of_match);
> > > > +	if (!psci_np)
> > > > +		return 0;
> > > > +
> > > > +	np = of_find_node_by_name(psci_np, "reset-types");
> > > > +	if (!np)
> > > > +		return 0;
> > > > +
> > > > +	for_each_property_of_node(np, prop) {
> > > > +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> > > > +			continue;
> > > > +		num = of_property_count_u32_elems(np, prop->name);
> > > > +		if (num != 1 && num != 2)
> > > > +			continue;
> > > > +
> > > > +		count++;
> > > > +	}
> > > > +
> > > > +	param = psci_reset_params =
> > > > +		kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL);
> > > > +	if (!psci_reset_params)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	for_each_property_of_node(np, prop) {
> > > > +		if (strncmp(prop->name, REBOOT_PREFIX, len))
> > > > +			continue;
> > > > +
> > > > +		param->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
> > > 
> > > FWIW - I think you need to keep the logic in the previous loop into account
> > > because that's what is used to allocate param, it is not a given that
> > > param is valid at this stage if I am not mistaken - the previous loop
> > > checked:
> > > 
> > > 	num = of_property_count_u32_elems(np, prop->name);
> > > 	if (num != 1 && num != 2)
> > > 		continue;
> > 
> > of_property_read_variable_u32_array() performs effectively the same
> > check.  It returns -EOVERFLOW if it couldn't find enough (== 0) or too
> > many values (>2). I currently have the added bonus of complaining in
> > dmesg about the bad reboot mode property, instead of silently ignoring.
> 
> Right but we are dereferencing param (param->mode) before carrying out that
> check.
> 

Ah, right, I see the problem. I'll send out another version after
settling on the other part of the discussion!

Thanks,
Elliot