[V2,24/30] serial: qcom: Migrate to dev_pm_opp_set_config()

The OPP core now provides a unified API for setting all configuration
types, i.e. dev_pm_opp_set_config().

Lets start using it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

On 01-07-22, 11:39, Greg Kroah-Hartman wrote:
> It's now more complex for simple drivers like this, right?

They need to add a structure, yes.

> Why not
> provide translations of the devm_pm_opp_set_clkname() to use internally
> devm_pm_opp_set_config() if you want to do complex things,

That can be done, yes.

> allowing you
> to continue to do simple things without the overhead of a driver having
> to create a structure on the stack

I didn't think of it as complexity, and I still feel it is okay-ish.

> and remember how the "const char *[]"
> syntax looks like (seriously, that's crazy).

The syntax can be fixed, if we want, by avoiding the cast with
something like this:

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index a018b45c5a9a..1a5480214a43 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -2559,8 +2559,9 @@ static int sdhci_msm_probe(struct platform_device *pdev)
        const struct sdhci_msm_offset *msm_offset;
        const struct sdhci_msm_variant_info *var_info;
        struct device_node *node = pdev->dev.of_node;
+       const char *clks[] = { "core" };
        struct dev_pm_opp_config opp_config = {
-               .clk_names = (const char *[]){ "core" },
+               .clk_names = clks,
                .clk_count = 1,
        };

> Make it simple for simple things, and provide the ability to do complex
> things only if that is required.

I still feel it isn't too bad for simple cases right now too, it is
just a structure to fill out but I don't have hard feelings for
keeping the old API around. I just feel it isn't too helpful to keep
the old interfaces around, it will just confuse people at the best.

Anyway, I will keep them around.

On Fri, Jul 01, 2022 at 03:59:26PM +0530, Viresh Kumar wrote:
> On 01-07-22, 12:18, Greg Kroah-Hartman wrote:
> > On Fri, Jul 01, 2022 at 03:31:00PM +0530, Viresh Kumar wrote:
> > Still crazy, but a bit better.
> 
> :)
> 
> > Why do you need the clk_count?  A null terminated list is better,
> 
> Because I am not a big fan of the null terminated lists :)
> 
> I had to chase a bug once where someone removed that NULL at the end
> and it was a nightmare to understand what's going on.

But that's the "normal" way the kernel does things.  Trying to keep a
count in sync with a list is a pain, and just gets harder and harder
over time.  Make it a null-terminated list so that the cpu makes this
always work and prevents errors.

> > as the
> > compiler can do it for you and you do not have to keep things in sync
> > like you are expecting people to be forced to do now.
> 
> I am not sure I understand what the compiler can do for us here.
> 
> The users will be required to do this here, isn't it ?
> 
>         const char *clks[] = { "core", NULL };
>         struct dev_pm_opp_config opp_config = {
>                .clk_names = clks,
>         };
> 

The "in sync" is the count issue.  Don't force humans to count up the
number of items in a list please.

> > The above is much more complex than a simple function call to make.
> > Remember to make it very simple for driver authors, and more
> > importantly, reviewers.
> 
> Hmm.
> 
> > Thanks, and drop the count field please.
> 
> There is one case at least [1] where we actually have to pass NULL in
> the clk name. This is basically to allow the same code to run on
> different devices, one where an OPP table is present and one where it
> isn't. We don't want to do clk_set_rate() for the second case but just
> use dev_pm_opp_set_rate() (which does a lot of stuff apart from just
> clk).

That feels completely wrong, don't have NULL for a name, make a fake name
or something.  Don't make all users in the kernel have a horrible
interface just for one piece of broken hardware out there.

Worst case, name it "".

thanks,

greg k-h

On 01-07-22, 12:41, Greg Kroah-Hartman wrote:
> That feels completely wrong, don't have NULL for a name, make a fake name
> or something.  Don't make all users in the kernel have a horrible
> interface just for one piece of broken hardware out there.
> 
> Worst case, name it "".

This name goes into the second argument of clk_get(dev, const char *con_id);

I will see how else I should hack it :)