[PATCH] drm/ast: Fix modeset failed on DisplayPort

[Jammy Huang]

Hi Thomas,

Thanks, I will modify the patch accordingly.

On 2023/5/24 下午 06:47, Thomas Zimmermann wrote:
> Hi,
>
> this patch also fell through the cracks. Apologies.
>
> Am 24.05.23 um 04:29 schrieb Jammy Huang:
>> Hi Thomas,
>>
>> Do you have other suggestion for this patch??
>
> The main issue was that struct ast_private is now called struct 
> ast_device.  So the current patch cannot be applied.
>
>>
>> Please kindly advise.
>>
>> On 2023/4/25 下午 03:39, Jammy Huang wrote:
>>> Hi Thomas,
>>>
>>> I think DP501 is OK. It doesn't use ioregs in ast_dp501_read_edid().
>>>
>>> On 2023/4/25 下午 03:27, Thomas Zimmermann wrote:
>>>> Hi
>>>>
>>>> Am 25.04.23 um 09:03 schrieb Jammy Huang:
>>>>> If we switch display and update cursor together, it could lead to
>>>>> modeset failed because of concurrent access to IO registers.
>>>>>
>>>>> Add lock protection in DP's edid access to avoid this problem.
>>>>
>>>> Thanks for the patch. I thought I fixed this issue already, but 
>>>> that apparently only happened for SIL164 and VGA.
>>>>
>>>> What about ast_dp501_connector_helper_get_modes()? Does it require 
>>>> the locking as well?
>>>>
>>>>>
>>>>> Signed-off-by: Jammy Huang <jammy_huang at aspeedtech.com>
>>>>> ---
>>>>>   drivers/gpu/drm/ast/ast_mode.c | 11 +++++++++++
>>>>>   1 file changed, 11 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/ast/ast_mode.c 
>>>>> b/drivers/gpu/drm/ast/ast_mode.c
>>>>> index 984ec590a7e7..fe5f1fd61361 100644
>>>>> --- a/drivers/gpu/drm/ast/ast_mode.c
>>>>> +++ b/drivers/gpu/drm/ast/ast_mode.c
>>>>> @@ -1635,6 +1635,8 @@ static int ast_dp501_output_init(struct 
>>>>> ast_private *ast)
>>>>>   static int ast_astdp_connector_helper_get_modes(struct 
>>>>> drm_connector *connector)
>>>>>   {
>>>>>       void *edid;
>>>>> +    struct drm_device *dev = connector->dev;
>>>>> +    struct ast_private *ast = to_ast_private(dev);
>>>>
>>>> We've meanwhile renamed ast_private to ast_device. Could you please 
>>>> provide an updated patch for the drm-misc-next tree?
>>>>
>>>> Best regards
>>>> Thomas
>>>>
>>>>>         int succ;
>>>>>       int count;
>>>>> @@ -1643,10 +1645,18 @@ static int 
>>>>> ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
>>>>>       if (!edid)
>>>>>           goto err_drm_connector_update_edid_property;
>>>>>   +    /*
>>>>> +     * Protect access to I/O registers from concurrent modesetting
>>>>> +     * by acquiring the I/O-register lock.
>>>>> +     */
>>>>> +    mutex_lock(&ast->ioregs_lock);
>>>>> +
>>>>>       succ = ast_astdp_read_edid(connector->dev, edid);
>>>>>       if (succ < 0)
>>>>>           goto err_kfree;
>>>>>   +    mutex_unlock(&ast->ioregs_lock);
>>>>> +
>>>>>       drm_connector_update_edid_property(connector, edid);
>>>>>       count = drm_add_edid_modes(connector, edid);
>>>>>       kfree(edid);
>>>>> @@ -1654,6 +1664,7 @@ static int 
>>>>> ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
>>>>>       return count;
>>>>>     err_kfree:
>
> Here's a minor issue that the goto label should now be called 
> err_mutex_unlock.
>
> Best regards
> Thomas
>
>>>>> + mutex_unlock(&ast->ioregs_lock);
>>>>>       kfree(edid);
>>>>>   err_drm_connector_update_edid_property:
>>>>>       drm_connector_update_edid_property(connector, NULL);
>>>>>
>>>>> base-commit: 61d325dcbc05d8fef88110d35ef7776f3ac3f68b
>>>>
>
-- 
Best Regards
Jammy