linux-kernel - Re: [PATCH] drm/msm/dp: update is_connected status base on sink count at dp_pm

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Message-ID: <781ad3c4973b3f8dd83933a451b266b9@codeaurora.org>
Date:   Mon, 02 Aug 2021 09:10:06 -0700
From:   khsieh@...eaurora.org
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, robdclark@...il.com,
        sean@...rly.run, vkoul@...nel.org, abhinavk@...eaurora.org,
        aravindh@...eaurora.org, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dp: update is_connected status base on sink count
 at dp_pm_resume()

On 2021-07-30 11:57, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2021-07-28 14:30:54)
>> Currently at dp_pm_resume() is_connected state is decided base on hpd 
>> connection
>> status only. This will put is_connected in wrongly "true" state at the 
>> scenario
>> that dongle attached to DUT but without hmdi cable connecting to it. 
>> Fix this
>> problem by adding read sink count from dongle and decided is_connected 
>> state base
>> on both sink count and hpd connection status.
>> 
> 
> Please add a Fixes tag.
> 
>> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
>> ---
>>  drivers/gpu/drm/msm/dp/dp_display.c | 23 +++++++++++++++++++++--
>>  1 file changed, 21 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
>> b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 2b660e9..9bcb261 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -1308,6 +1308,17 @@ static int dp_display_remove(struct 
>> platform_device *pdev)
>>         return 0;
>>  }
>> 
>> +static int dp_get_sink_count(struct dp_display_private *dp)
>> +{
>> +       u8 sink_count;
>> +
>> +       sink_count = drm_dp_read_sink_count(dp->aux);
> 
> drm_dp_read_sink_count() returns an int, not a u8. Comparing a u8 to
> less than zero doesn't make any sense as it isn't signed.
> 
>> +       if (sink_count < 0)
>> +               return 0;
>> +
>> +       return sink_count;
>> +}
> 
> We can drop this function and just have an int count in dp_pm_resume()
> that is compared to < 0 and then ignored.
> 
>> +
>>  static int dp_pm_resume(struct device *dev)
>>  {
>>         struct platform_device *pdev = to_platform_device(dev);
>> @@ -1327,14 +1338,22 @@ static int dp_pm_resume(struct device *dev)
>> 
>>         dp_catalog_ctrl_hpd_config(dp->catalog);
>> 
>> -       status = dp_catalog_link_is_connected(dp->catalog);
>> +       /*
>> +        * set sink to normal operation mode -- D0
>> +        * before dpcd read
>> +        */
>> +       dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>> 
>> +       if ((status = dp_catalog_link_is_connected(dp->catalog)))
>> +               dp->link->sink_count = dp_get_sink_count(dp);
> 
> Do we need to call drm_dp_read_sink_count_cap() as well?
no, we only need sink_count
> 
>> +       else
>> +               dp->link->sink_count = 0;
>>         /*
>>          * can not declared display is connected unless
>>          * HDMI cable is plugged in and sink_count of
>>          * dongle become 1
>>          */
>> -       if (status && dp->link->sink_count)
> 
> Is 'status' used anymore? If not, please remove it.
Yes, it still used which used to decided to perform dpcd read sink count 
or not
> 
>> +       if (dp->link->sink_count)
>>                 dp->dp_display.is_connected = true;
>>         else
>>                 dp->dp_display.is_connected = false;