Re: [PATCH 2/4] drm/i915/lpt: Avoid early timeout during FDI PHY reset

Tvrtko Ursulin
2016-06-28T11:12:14Z

On 28/06/16 11:37, Imre Deak wrote:
> Since wait_for_atomic doesn't re-check the wait-for condition after
> expiry of the timeout it can fail when called from non-atomic context
> even if the condition is set correctly before the expiry. Fix this by
> using the non-atomic wait_for instead.
>
> Fixes: 0351b93992aa ("drm/i915: Do not lie about atomic timeout granularity")
> CC: Chris Wilson <chris@chris-wilson.co.uk>
> CC: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
> drivers/gpu/drm/i915/intel_display.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index c3b5dc8..0312472 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -8537,16 +8537,16 @@ static void lpt_reset_fdi_mphy(struct drm_i915_private *dev_priv)
> tmp |= FDI_MPHY_IOSFSB_RESET_CTL;
> I915_WRITE(SOUTH_CHICKEN2, tmp);
>
> - if (wait_for_atomic_us(I915_READ(SOUTH_CHICKEN2) &
> - FDI_MPHY_IOSFSB_RESET_STATUS, 100))
> + if (wait_for_us(I915_READ(SOUTH_CHICKEN2) &
> + FDI_MPHY_IOSFSB_RESET_STATUS, 100))
> DRM_ERROR("FDI mPHY reset assert timeout\n");
>
> tmp = I915_READ(SOUTH_CHICKEN2);
> tmp &= ~FDI_MPHY_IOSFSB_RESET_CTL;
> I915_WRITE(SOUTH_CHICKEN2, tmp);
>
> - if (wait_for_atomic_us((I915_READ(SOUTH_CHICKEN2) &
> - FDI_MPHY_IOSFSB_RESET_STATUS) == 0, 100))
> + if (wait_for_us((I915_READ(SOUTH_CHICKEN2) &
> + FDI_MPHY_IOSFSB_RESET_STATUS) == 0, 100))
> DRM_ERROR("FDI mPHY reset de-assert timeout\n");
> }

This one was easy to find non-atomic context is correct.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko