diff mbox series

[v3,07/11] bus: mhi: host: Add support to read MHI capabilities

Message ID 20250519-mhi_bw_up-v3-7-3acd4a17bbb5@oss.qualcomm.com
State New
Headers show
Series bus: mhi: host: Add support for mhi bus bw | expand

Commit Message

Krishna Chaitanya Chundru May 19, 2025, 9:42 a.m. UTC 
From: Vivek Pernamitta <quic_vpernami@quicinc.com>

As per MHI spec v1.2,sec 6.6, MHI has capability registers which are
located after the ERDB array. The location of this group of registers is
indicated by the MISCOFF register. Each capability has a capability ID to
determine which functionality is supported and each capability will point
to the next capability supported.

Add a basic function to read those capabilities offsets.

Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
 drivers/bus/mhi/common.h    |  4 ++++
 drivers/bus/mhi/host/init.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

Comments

Jeffrey Hugo May 21, 2025, 2:52 p.m. UTC | #1 
On 5/19/2025 3:42 AM, Krishna Chaitanya Chundru wrote:
> From: Vivek Pernamitta <quic_vpernami@quicinc.com>
> 
> As per MHI spec v1.2,sec 6.6, MHI has capability registers which are
> located after the ERDB array. The location of this group of registers is
> indicated by the MISCOFF register. Each capability has a capability ID to
> determine which functionality is supported and each capability will point
> to the next capability supported.
> 
> Add a basic function to read those capabilities offsets.
> 
> Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
> ---
>   drivers/bus/mhi/common.h    |  4 ++++
>   drivers/bus/mhi/host/init.c | 29 +++++++++++++++++++++++++++++
>   2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
> index dda340aaed95a5573a2ec776ca712e11a1ed0b52..eedac801b80021e44f7c65d33cd50760e06c02f2 100644
> --- a/drivers/bus/mhi/common.h
> +++ b/drivers/bus/mhi/common.h
> @@ -16,6 +16,7 @@
>   #define MHICFG				0x10
>   #define CHDBOFF				0x18
>   #define ERDBOFF				0x20
> +#define MISCOFF				0x24
>   #define BHIOFF				0x28
>   #define BHIEOFF				0x2c
>   #define DEBUGOFF			0x30
> @@ -113,6 +114,9 @@
>   #define MHISTATUS_MHISTATE_MASK		GENMASK(15, 8)
>   #define MHISTATUS_SYSERR_MASK		BIT(2)
>   #define MHISTATUS_READY_MASK		BIT(0)
> +#define MISC_CAP_MASK			GENMASK(31, 0)
> +#define CAP_CAPID_MASK			GENMASK(31, 24)
> +#define CAP_NEXT_CAP_MASK		GENMASK(23, 12)
>   
>   /* Command Ring Element macros */
>   /* No operation command */
> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> index 13e7a55f54ff45b83b3f18b97e2cdd83d4836fe3..a7137a040bdce1c58c98fe9c2340aae4cc4387d1 100644
> --- a/drivers/bus/mhi/host/init.c
> +++ b/drivers/bus/mhi/host/init.c
> @@ -467,6 +467,35 @@ int mhi_init_dev_ctxt(struct mhi_controller *mhi_cntrl)
>   	return ret;
>   }
>   
> +static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 capability, u32 *offset)
> +{
> +	u32 val, cur_cap, next_offset;
> +	int ret;
> +
> +	/* Get the 1st supported capability offset */

"first"?  Does not seem like you are short on space here.

> +	ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MISCOFF,
> +				 MISC_CAP_MASK, offset);

This fits on one line.

> +	if (ret)
> +		return ret;

Blank line here would be nice.

> +	do {
> +		if (*offset >= mhi_cntrl->reg_len)
> +			return -ENXIO;
> +
> +		ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, *offset, &val);
> +		if (ret)
> +			return ret;


There is no sanity checking we can do on val?  We've had plenty of 
issues blindly trusting the device.  I would like to avoid having more.

Also looks like if we find the capability we are looking for, we return 
the offset without validating it.

> +
> +		cur_cap = FIELD_GET(CAP_CAPID_MASK, val);
> +		next_offset = FIELD_GET(CAP_NEXT_CAP_MASK, val);
> +		if (cur_cap == capability)
> +			return 0;
> +
> +		*offset = next_offset;
> +	} while (next_offset);
> +
> +	return -ENXIO;
> +}
> +
>   int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
>   {
>   	u32 val;
>
diff mbox series

Patch

diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
index dda340aaed95a5573a2ec776ca712e11a1ed0b52..eedac801b80021e44f7c65d33cd50760e06c02f2 100644
--- a/drivers/bus/mhi/common.h
+++ b/drivers/bus/mhi/common.h
@@ -16,6 +16,7 @@ 
 #define MHICFG				0x10
 #define CHDBOFF				0x18
 #define ERDBOFF				0x20
+#define MISCOFF				0x24
 #define BHIOFF				0x28
 #define BHIEOFF				0x2c
 #define DEBUGOFF			0x30
@@ -113,6 +114,9 @@ 
 #define MHISTATUS_MHISTATE_MASK		GENMASK(15, 8)
 #define MHISTATUS_SYSERR_MASK		BIT(2)
 #define MHISTATUS_READY_MASK		BIT(0)
+#define MISC_CAP_MASK			GENMASK(31, 0)
+#define CAP_CAPID_MASK			GENMASK(31, 24)
+#define CAP_NEXT_CAP_MASK		GENMASK(23, 12)
 
 /* Command Ring Element macros */
 /* No operation command */
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index 13e7a55f54ff45b83b3f18b97e2cdd83d4836fe3..a7137a040bdce1c58c98fe9c2340aae4cc4387d1 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -467,6 +467,35 @@  int mhi_init_dev_ctxt(struct mhi_controller *mhi_cntrl)
 	return ret;
 }
 
+static int mhi_find_capability(struct mhi_controller *mhi_cntrl, u32 capability, u32 *offset)
+{
+	u32 val, cur_cap, next_offset;
+	int ret;
+
+	/* Get the 1st supported capability offset */
+	ret = mhi_read_reg_field(mhi_cntrl, mhi_cntrl->regs, MISCOFF,
+				 MISC_CAP_MASK, offset);
+	if (ret)
+		return ret;
+	do {
+		if (*offset >= mhi_cntrl->reg_len)
+			return -ENXIO;
+
+		ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, *offset, &val);
+		if (ret)
+			return ret;
+
+		cur_cap = FIELD_GET(CAP_CAPID_MASK, val);
+		next_offset = FIELD_GET(CAP_NEXT_CAP_MASK, val);
+		if (cur_cap == capability)
+			return 0;
+
+		*offset = next_offset;
+	} while (next_offset);
+
+	return -ENXIO;
+}
+
 int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
 {
 	u32 val;