[PATCH v2] drm/ast: Fix ast_dp connection status

[Jocelyn Falempe]

On 27/01/2025 12:55, Thomas Zimmermann wrote:
> Hi
> 
> 
> Am 24.01.25 um 15:11 schrieb Jocelyn Falempe:
>> ast_dp_is_connected() used to also check for link training success
>> to report the DP connector as connected. Without this check, the
>> physical_status is always connected. So if no monitor is present, it
>> will fail to read the EDID and set the default resolution to 640x480
>> instead of 1024x768.
>>
>> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
>> Fixes: 2281475168d2 ("drm/ast: astdp: Perform link training during 
>> atomic_enable")
>> Cc: Thomas Zimmermann <tzimmermann at suse.de>
>> Cc: Dave Airlie <airlied at redhat.com>
>> Cc: dri-devel at lists.freedesktop.org
>> Cc: <stable at vger.kernel.org> # v6.12+
> 
> I cannot reproduce the problem, but the patch looks correct. My AST2600 
> with ASTDP still works correctly with the patch allied.

Thanks, interesting that it doesn't affect all hardwares.
I got reports from two different vendors about this issue.

If no other comments, I will push it to drm-misc-next tomorrow (only 
adding reported-by: and tested-by: tags).

-- 

Jocelyn

> 
> Reviewed-by: Thomas Zimmermann <tzimmermann at suse.de>
> 
> Best regards
> Thomas
> 
>> ---
>>   drivers/gpu/drm/ast/ast_dp.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c
>> index 0e282b7b167c..30aad5c0112a 100644
>> --- a/drivers/gpu/drm/ast/ast_dp.c
>> +++ b/drivers/gpu/drm/ast/ast_dp.c
>> @@ -17,6 +17,12 @@ static bool ast_astdp_is_connected(struct 
>> ast_device *ast)
>>   {
>>       if (!ast_get_index_reg_mask(ast, AST_IO_VGACRI, 0xDF, 
>> AST_IO_VGACRDF_HPD))
>>           return false;
>> +    /*
>> +     * HPD might be set even if no monitor is connected, so also 
>> check that
>> +     * the link training was successful.
>> +     */
>> +    if (!ast_get_index_reg_mask(ast, AST_IO_VGACRI, 0xDC, 
>> AST_IO_VGACRDC_LINK_SUCCESS))
>> +        return false;
>>       return true;
>>   }
>>
>> base-commit: 798047e63ac970f105c49c22e6d44df901c486b2
>