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

[Jammy Huang <jammy_huang@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
> > > > > ---
> > > > >   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