linux-kernel - Re: [PATCH] drm/bridge: analogix: Don't return -EINVAL when panel not support PSR in PSR functions

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Date:   Fri, 2 Dec 2016 11:03:09 -0500
From:   Sean Paul <seanpaul@...omium.org>
To:     Archit Taneja <architt@...eaurora.org>
Cc:     zain wang <wzz@...k-chips.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        David Airlie <airlied@...ux.ie>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Mika Kahola <mika.kahola@...el.com>,
        Stéphane Marchesin <marcheu@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Thierry Reding <treding@...dia.com>,
        Krzysztof Kozlowski <k.kozlowski@...sung.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Jingoo Han <jingoohan1@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH] drm/bridge: analogix: Don't return -EINVAL when panel not
 support PSR in PSR functions

On Thu, Dec 1, 2016 at 10:54 PM, Archit Taneja <architt@...eaurora.org> wrote:
> Hi,
>
> On 12/02/2016 08:02 AM, zain wang wrote:
>>
>> We will ignored PSR setting if panel not support it. So, in this case, we
>> should
>> return from analogix_dp_enable/disable_psr() without any error code.
>> Let's retrun 0 instead of -EINVAL when panel not support PSR in
>> analogix_dp_enable/disable_psr().
>>
>> Signed-off-by: zain wang <wzz@...k-chips.com>
>> ---
>>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> index 6e0447f..0cb3695 100644
>> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
>> @@ -112,7 +112,7 @@ int analogix_dp_enable_psr(struct device *dev)
>>         struct edp_vsc_psr psr_vsc;
>>
>>         if (!dp->psr_support)
>> -               return -EINVAL;
>> +               return 0;
>
>
> Looking at the rockchip analogix dp code, in analogix_dp_psr_set, the worker
> that calls
> analogix_dp_enable/disable_psr isn't even if psr isn't enabled. So, the
> bridge funcs
> shouldn't be called in the first place. I think the error handling is fine
> to have
> here.
>

Hi Archit,

This was my first impression, too, and the complexity of the various
psr abstraction layers don't help :)

However, this code path will be hit if the source supports psr, but
the sink doesn't. The rockchip_drm_psr code doesn't know if the sink
supports psr, so it will end up calling this.

Sean


>>
>>         /* Prepare VSC packet as per EDP 1.4 spec, Table 6.9 */
>>         memset(&psr_vsc, 0, sizeof(psr_vsc));
>> @@ -135,7 +135,7 @@ int analogix_dp_disable_psr(struct device *dev)
>>         struct edp_vsc_psr psr_vsc;
>>
>>         if (!dp->psr_support)
>> -               return -EINVAL;
>> +               return 0;
>>
>>         /* Prepare VSC packet as per EDP 1.4 spec, Table 6.9 */
>>         memset(&psr_vsc, 0, sizeof(psr_vsc));
>> @@ -878,6 +878,8 @@ static void analogix_dp_commit(struct
>> analogix_dp_device *dp)
>>         dp->psr_support = analogix_dp_detect_sink_psr(dp);
>>         if (dp->psr_support)
>>                 analogix_dp_enable_sink_psr(dp);
>> +       else
>> +               dev_warn(dp->dev, "Sink not support PSR\n");
>
>
> This doesn't seem beneficial either. There seems to be a debug
> print already in analogix_dp_detect_sink_psr which reports PSR
> related info.
>
> Archit
>
>>  }
>>
>>  /*
>>
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project