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SubjectRe: [PATCH v2 07/15] drm/mxsfb: Fix the vblank events
On Wed, Aug 14, 2019 at 01:48:43PM +0300, Robert Chiras wrote:
> Currently, the vblank support is not correctly implemented in MXSFB_DRM
> driver. The call to drm_vblank_init is made with mode_config.num_crtc
> which at that time is 0. Because of this, vblank is not activated, so
> there won't be any vblank event submitted.
> For example, when running modetest with the '-v' parameter will result
> in an astronomical refresh rate (10000+ Hz), because of that.

Uh, that sounds a bit like a bug somewhere. If vblank doesn't work, we
should give userspace an error back.

Maybe we need more checks in drm_vblank_init()? Can you pls look into
that?

>
> Signed-off-by: Robert Chiras <robert.chiras@nxp.com>
> ---
> drivers/gpu/drm/mxsfb/mxsfb_drv.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index 2743975..829abec 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -38,6 +38,9 @@
> #include "mxsfb_drv.h"
> #include "mxsfb_regs.h"
>
> +/* The eLCDIF max possible CRTCs */
> +#define MAX_CRTCS 1
> +
> enum mxsfb_devtype {
> MXSFB_V3,
> MXSFB_V4,
> @@ -138,6 +141,8 @@ static void mxsfb_pipe_enable(struct drm_simple_display_pipe *pipe,
> mxsfb->connector = &mxsfb->panel_connector;
> }
>
> + drm_crtc_vblank_on(&pipe->crtc);
> +
> pm_runtime_get_sync(drm->dev);
> drm_panel_prepare(mxsfb->panel);
> mxsfb_crtc_enable(mxsfb);
> @@ -164,6 +169,8 @@ static void mxsfb_pipe_disable(struct drm_simple_display_pipe *pipe)
> }
> spin_unlock_irq(&drm->event_lock);
>
> + drm_crtc_vblank_off(&pipe->crtc);
> +
> if (mxsfb->connector != &mxsfb->panel_connector)
> mxsfb->connector = NULL;
> }
> @@ -246,7 +253,7 @@ static int mxsfb_load(struct drm_device *drm, unsigned long flags)
>
> pm_runtime_enable(drm->dev);
>
> - ret = drm_vblank_init(drm, drm->mode_config.num_crtc);
> + ret = drm_vblank_init(drm, MAX_CRTCS);
> if (ret < 0) {
> dev_err(drm->dev, "Failed to initialise vblank\n");
> goto err_vblank;
> @@ -269,6 +276,8 @@ static int mxsfb_load(struct drm_device *drm, unsigned long flags)
> goto err_vblank;
> }
>
> + drm_crtc_vblank_off(&mxsfb->pipe.crtc);

Are you sure you need this one here? vblanks should be off after
drm_vblank_init() is called.

Thanks, Daniel

> +
> /*
> * Attach panel only if there is one.
> * If there is no panel attach, it must be a bridge. In this case, we
> --
> 2.7.4
>

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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