[PATCH] drm/ast: Fix default resolution when no monitor is connected on DP

[Thomas Zimmermann]

(cc: some people from commit fae7d186403e)

Am 04.07.23 um 16:19 schrieb Thomas Zimmermann:
> Hi Jocelyn
> 
> Am 23.06.23 um 11:46 schrieb Jocelyn Falempe:
>> Since commit fae7d186403e ("drm/probe-helper: Default to 640x480 if no
>>   EDID on DP")
>> The default resolution is now 640x480 when no monitor is connected.
>> But Aspeed graphics is mostly used in servers, where no monitor
>> is attached. This also affects the "remote" resolution to 640x480, 
>> which is
>> inconvenient, and breaks the anaconda installer.
> 
> By "remote resolution", you mean the display mode that the BMC uses?
> 
>> So when no EDID is present, set 1024x768 as preferred resolution.
>>
>> Fixes: fae7d186403e ("drm/probe-helper: Default to 640x480 if no EDID 
>> on DP")
> 
> This commit says that 640x480 is the designated failsafe mode if no EDID 
> is available. Therefore, I think we should not override it 
> unconditionally. The ast driver is no special in that case.
> 
> But I see why you're doing this change. I think any solution should be 
> implemented in drm_helper_probe_single_connector_modes().
> 
> But before we solve this in the kernel, is it possible to delegate this 
> to userspace? If no EDID has been given, userspace could try a 
> non-failsafe display mode.
> 
> Best regards
> Thomas
> 
>> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
>> ---
>>   drivers/gpu/drm/ast/ast_mode.c | 26 ++++++++++++++++++++++++--
>>   1 file changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_mode.c 
>> b/drivers/gpu/drm/ast/ast_mode.c
>> index 36374828f6c8..8f7b7cc021c7 100644
>> --- a/drivers/gpu/drm/ast/ast_mode.c
>> +++ b/drivers/gpu/drm/ast/ast_mode.c
>> @@ -1589,9 +1589,31 @@ static const struct drm_connector_helper_funcs 
>> ast_dp501_connector_helper_funcs
>>       .get_modes = ast_dp501_connector_helper_get_modes,
>>   };
>> +static int ast_dp_probe_single_connector_modes(struct drm_connector 
>> *connector,
>> +                           uint32_t maxX, uint32_t maxY)
>> +{
>> +    int ret;
>> +    struct drm_display_mode *mode;
>> +
>> +    ret = drm_helper_probe_single_connector_modes(connector, maxX, 
>> maxY);
>> +    /*
>> +     * When no monitor are detected, DP now default to 640x480
>> +     * As aspeed is mostly used in remote server, and DP monitors are
>> +     * rarely attached, it's better to default to 1024x768
>> +     */
>> +    if (!connector->edid_blob_ptr) {
>> +        list_for_each_entry(mode, &connector->modes, head) {
>> +            if (mode->hdisplay == 1024 && mode->vdisplay == 768)
>> +                mode->type |= DRM_MODE_TYPE_PREFERRED;
>> +            drm_mode_sort(&connector->modes);
>> +        }
>> +    }
>> +    return ret;
>> +}
>> +
>>   static const struct drm_connector_funcs ast_dp501_connector_funcs = {
>>       .reset = drm_atomic_helper_connector_reset,
>> -    .fill_modes = drm_helper_probe_single_connector_modes,
>> +    .fill_modes = ast_dp_probe_single_connector_modes,
>>       .destroy = drm_connector_cleanup,
>>       .atomic_duplicate_state = 
>> drm_atomic_helper_connector_duplicate_state,
>>       .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
>> @@ -1678,7 +1700,7 @@ static const struct drm_connector_helper_funcs 
>> ast_astdp_connector_helper_funcs
>>   static const struct drm_connector_funcs ast_astdp_connector_funcs = {
>>       .reset = drm_atomic_helper_connector_reset,
>> -    .fill_modes = drm_helper_probe_single_connector_modes,
>> +    .fill_modes = ast_dp_probe_single_connector_modes,
>>       .destroy = drm_connector_cleanup,
>>       .atomic_duplicate_state = 
>> drm_atomic_helper_connector_duplicate_state,
>>       .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
>>
>> base-commit: 0adec22702d497385dbdc52abb165f379a00efba
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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