[PATCH] drm/i915: fix FDI_RX_CHICKEN register read masking

[PATCH] drm/i915: fix FDI_RX_CHICKEN register read masking

[Jani Nikula]

Mask the value, not the register. Spotted while reading the code.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

---

Only compile tested. Is there a bug that might match this?
---
 drivers/gpu/drm/i915/intel_display.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a5be346..6f8cf2a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2804,8 +2804,8 @@ static void ironlake_fdi_disable(struct drm_crtc *crtc)
 	if (HAS_PCH_IBX(dev)) {
 		I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR);
 		I915_WRITE(FDI_RX_CHICKEN(pipe),
-			   I915_READ(FDI_RX_CHICKEN(pipe) &
-				     ~FDI_RX_PHASE_SYNC_POINTER_EN));
+			   I915_READ(FDI_RX_CHICKEN(pipe)) &
+			   ~FDI_RX_PHASE_SYNC_POINTER_EN);
 	} else if (HAS_PCH_CPT(dev)) {
 		cpt_phase_pointer_disable(dev, pipe);
 	}
-- 
1.7.9.5

Re: [PATCH] drm/i915: fix FDI_RX_CHICKEN register read masking

[Lespiau, Damien]

On Mon, Oct 29, 2012 at 5:26 PM, Jani Nikula <jani.nikula@intel.com> wrote:
> Mask the value, not the register. Spotted while reading the code.
>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>

Good catch! FWIW, I ran:

git grep -e "READ.*\(pipe\|plane\|cpu_transcoder\))[^)]*[|&]"
drivers/gpu/drm/i915/

and this was the only catch.

-- 
Damien


> ---
>
> Only compile tested. Is there a bug that might match this?
> ---
>  drivers/gpu/drm/i915/intel_display.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index a5be346..6f8cf2a 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2804,8 +2804,8 @@ static void ironlake_fdi_disable(struct drm_crtc *crtc)
>         if (HAS_PCH_IBX(dev)) {
>                 I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR);
>                 I915_WRITE(FDI_RX_CHICKEN(pipe),
> -                          I915_READ(FDI_RX_CHICKEN(pipe) &
> -                                    ~FDI_RX_PHASE_SYNC_POINTER_EN));
> +                          I915_READ(FDI_RX_CHICKEN(pipe)) &
> +                          ~FDI_RX_PHASE_SYNC_POINTER_EN);
>         } else if (HAS_PCH_CPT(dev)) {
>                 cpt_phase_pointer_disable(dev, pipe);
>         }
> --
> 1.7.9.5
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [PATCH] drm/i915: fix FDI_RX_CHICKEN register read masking

[Daniel Vetter]

On Mon, Oct 29, 2012 at 05:49:48PM +0000, Lespiau, Damien wrote:
> On Mon, Oct 29, 2012 at 5:26 PM, Jani Nikula <jani.nikula@intel.com> wrote:
> > Mask the value, not the register. Spotted while reading the code.
> >
> > Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> 
> Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>

Queued for -next, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [PATCH] drm/i915: fix FDI_RX_CHICKEN register read masking

[Daniel Vetter]

On Mon, Oct 29, 2012 at 07:26:42PM +0200, Jani Nikula wrote:
> Mask the value, not the register. Spotted while reading the code.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> 
> ---
> 
> Only compile tested. Is there a bug that might match this?
> ---
>  drivers/gpu/drm/i915/intel_display.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index a5be346..6f8cf2a 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2804,8 +2804,8 @@ static void ironlake_fdi_disable(struct drm_crtc *crtc)
>  	if (HAS_PCH_IBX(dev)) {
>  		I915_WRITE(FDI_RX_CHICKEN(pipe), FDI_RX_PHASE_SYNC_POINTER_OVR);
>  		I915_WRITE(FDI_RX_CHICKEN(pipe),
> -			   I915_READ(FDI_RX_CHICKEN(pipe) &
> -				     ~FDI_RX_PHASE_SYNC_POINTER_EN));
> +			   I915_READ(FDI_RX_CHICKEN(pipe)) &
> +			   ~FDI_RX_PHASE_SYNC_POINTER_EN);

On second look, we write the same register in the previous line, and the
w/a seems to be to set FDI_RX_PHASE_SYNC_POINTER_OVR to enable the logic,
then keep always set FDI_RX_PHASE_SYNC_POINTER_OVR and toggle
~FDI_RX_PHASE_SYNC_POINTER_EN before/after enabling the pc transcoder. So
the right things seems to be to simply kill the 2nd write.
-Daniel

>  	} else if (HAS_PCH_CPT(dev)) {
>  		cpt_phase_pointer_disable(dev, pipe);
>  	}
> -- 
> 1.7.9.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch