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

[Jammy Huang]

Hi Thomas,

Do you have other suggestion for this patch??

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:
> > > +    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