Re: [PATCH 08/25] media: atmel: properly get pm_runtime

Em Thu, 10 Jun 2021 12:00:42 +0000
[off-list ref] escreveu:

On 6/10/21 12:38 PM, Mauro Carvalho Chehab wrote:

quoted

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Em Thu, 10 Jun 2021 09:04:07 +0000
[off-list ref] escreveu:
  

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diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
index fe3ec8d0eaee..ce8e1351fa53 100644
--- a/drivers/media/platform/atmel/atmel-isc-base.c
+++ b/drivers/media/platform/atmel/atmel-isc-base.c

@@ -294,9 +294,13 @@ static int isc_wait_clk_stable(struct clk_hw *hw)
   static int isc_clk_prepare(struct clk_hw *hw)
   {
        struct isc_clk *isc_clk = to_isc_clk(hw);
+     int ret;

-     if (isc_clk->id == ISC_ISPCK)
-             pm_runtime_get_sync(isc_clk->dev);
+     if (isc_clk->id == ISC_ISPCK) {
+             ret = pm_runtime_resume_and_get(isc_clk->dev);
+             if (ret < 0)
+                     return ret;
+     }  

Hi Mauro,

With this patch, the ISC is broken on latest media tree. It looks like
pm_runtime_resume_and_get for the ISC_ISPCK clock returns -ENOACCESS and
thus, the probe of the driver fails:

atmel-sama5d2-isc f0008000.isc: failed to enable ispck: -13
atmel-sama5d2-isc: probe of f0008000.isc failed with error -13


Could you point out how I could fix this ? Maybe the isc_clk->dev is not
properly handled/initialized in some other part of the code ?  

Looking at RPM implementation:

         static int rpm_resume(struct device *dev, int rpmflags)
         {
...
         if (dev->power.runtime_error)
                 retval = -EINVAL;
         else if (dev->power.disable_depth == 1 && dev->power.is_suspended
             && dev->power.runtime_status == RPM_ACTIVE)
                 retval = 1;
         else if (dev->power.disable_depth > 0)
                 retval = -EACCES;
...

It sounds that RPM is disabled for this clock. Did you call
pm_runtime_enable() before calling isc_clk_prepare()?

Thanks,
Mauro
  

I tried to call pm_runtime_enable for the clk at clk_init time, but 
doing that makes the runtime for the ISC fail like this:

atmel-sama5d2-isc f0008000.isc: Unbalanced pm_runtime_enable!

Making RPM balanced is complex ;-)

Yet, clearly there's something weird at the PM code. I mean,
ignoring a -ENOACCESS error like the original code sounds wrong,
as it basically means that pm_runtime_get_sync() were doing
nothing (except by incrementing a refcount).

Some drivers call clk_prepare()/clk_unprepare() at their
.prepare/.unprepare ops. Those functions internally call
RPM get logic recursively, to ensure that the RPM
state of the parents are also at the right state.

Thanks,
Mauro

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