One comment bellow.
On 12/13/16 17:07, Bartosz Golaszewski wrote:
> Revision 2 of LCDC suffers from an issue where a SYNC_LOST error
> caused by limited memory bandwidth may leave the picture shifted a
> couple pixels to the right.
>
> This issue has not been observed on revision 1, while the recovery
> mechanism introduces a different issue, where the END_OF_FRAME
> interrupt doesn't fire while drm is waiting for vblanks.
>
> On rev1: recover from sync lost errors by simply clearing the
> RASTER_ENABLE bit in the RASTER_CTRL register and re-enabling it
> again as is suggested by the datasheet.
>
> Signed-off-by: Bartosz Golaszewski <bgolaszew...@baylibre.com>
> ---
> drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index 9942b05..70e57a7 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -921,17 +921,23 @@ irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc)
> dev_err_ratelimited(dev->dev, "%s(0x%08x): Sync lost",
> __func__, stat);
> tilcdc_crtc->frame_intact = false;
> - if (tilcdc_crtc->sync_lost_count++ >
> - SYNC_LOST_COUNT_LIMIT) {
> - dev_err(dev->dev, "%s(0x%08x): Sync lost flood
> detected, recovering", __func__, stat);
> - queue_work(system_wq, &tilcdc_crtc->recover_work);
> - if (priv->rev == 1)
> - tilcdc_clear(dev, LCDC_RASTER_CTRL_REG,
> - LCDC_V1_SYNC_LOST_INT_ENA);
> - else
> + if (priv->rev == 1) {
I would add here:
+ if ((tilcdc_read(dev, LCDC_RASTER_CTRL_REG) &
+ LCDC_RASTER_ENABLE)) {
> + tilcdc_clear(dev,
> + LCDC_RASTER_CTRL_REG, LCDC_RASTER_ENABLE);
> + tilcdc_set(dev,
> + LCDC_RASTER_CTRL_REG, LCDC_RASTER_ENABLE);
+ }
Just in case the interrupt is for some reason handled right after the
crtc is disabled.
With this addition I could send a pull request for this fix still today,
if you agree with the change.
> + } else {
> + if (tilcdc_crtc->sync_lost_count++ >
> + SYNC_LOST_COUNT_LIMIT) {
> + dev_err(dev->dev,
> + "%s(0x%08x): Sync lost flood detected,
> recovering",
> + __func__, stat);
> + queue_work(system_wq,
> + &tilcdc_crtc->recover_work);
> tilcdc_write(dev, LCDC_INT_ENABLE_CLR_REG,
> LCDC_SYNC_LOST);
> - tilcdc_crtc->sync_lost_count = 0;
> + tilcdc_crtc->sync_lost_count = 0;
> + }
> }
> }
>
>
