[PATCH] gpu: drm: Use devm_clk_get_enabled() helpers

[Rong Qianfeng]

在 2024/8/22 8:35, Julian Calaby 写道:
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>
> Hi Rong,
>
> On Tue, Aug 20, 2024 at 10:59 PM Rong Qianfeng <rongqianfeng at vivo.com> wrote:
>> Replace devm_clk_get() and clk_prepare_enable() with
>> devm_clk_get_enabled() that also disables and unprepares it on
>> driver detach.
>>
>> Signed-off-by: Rong Qianfeng <rongqianfeng at vivo.com>
>> ---
>>   drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 13 +++----------
>>   drivers/gpu/drm/sun4i/sun6i_drc.c         | 15 ++++-----------
>>   drivers/gpu/drm/sun4i/sun8i_mixer.c       | 13 +++----------
>>   3 files changed, 10 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/sun4i/sun6i_drc.c b/drivers/gpu/drm/sun4i/sun6i_drc.c
>> index 0d342f43fa93..f263ad282828 100644
>> --- a/drivers/gpu/drm/sun4i/sun6i_drc.c
>> +++ b/drivers/gpu/drm/sun4i/sun6i_drc.c
>> @@ -42,33 +42,28 @@ static int sun6i_drc_bind(struct device *dev, struct device *master,
>>                  return ret;
>>          }
>>
>> -       drc->bus_clk = devm_clk_get(dev, "ahb");
>> +       drc->bus_clk = devm_clk_get_enabled(dev, "ahb");
>>          if (IS_ERR(drc->bus_clk)) {
>>                  dev_err(dev, "Couldn't get our bus clock\n");
>>                  ret = PTR_ERR(drc->bus_clk);
>>                  goto err_assert_reset;
>>          }
>> -       clk_prepare_enable(drc->bus_clk);
>>
>> -       drc->mod_clk = devm_clk_get(dev, "mod");
>> +       drc->mod_clk = devm_clk_get_enabled(dev, "mod");
>>          if (IS_ERR(drc->mod_clk)) {
>>                  dev_err(dev, "Couldn't get our mod clock\n");
>>                  ret = PTR_ERR(drc->mod_clk);
>> -               goto err_disable_bus_clk;
>> +               goto err_assert_reset;
>>          }
>>
>>          ret = clk_set_rate_exclusive(drc->mod_clk, 300000000);
>>          if (ret) {
>>                  dev_err(dev, "Couldn't set the module clock frequency\n");
>> -               goto err_disable_bus_clk;
>> +               goto err_assert_reset;
>>          }
>>
>> -       clk_prepare_enable(drc->mod_clk);
> Am I reading this right: is this changing the init sequence so that
> the clock is enabled before setting a rate?
>
> This is the sort of thing that might cause glitches and issues in some
> hardware, so it'd be polite to test such a change on the actual
> hardware before posting it.

Hi Julian ,

I have seen this used in other places, but the problem you raised may be
different on different hardware.

I wonder if anyone can clarify this?

Best regards,
Qianfeng

>
> Thanks,
>
> --
> Julian Calaby
>
> Email: julian.calaby at gmail.com
> Profile: http://www.google.com/profiles/julian.calaby/