[Intel-gfx] [PATCH 4/7] drm/i915: Warn when DPIO read returns 0xffffffff

[Jesse Barnes]

On Mon, 31 Mar 2014 18:21:27 +0300
ville.syrjala at linux.intel.com wrote:

> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> DPIO reads from groups/broadcast register offsets for PCS and
> TX return all 1's. If that result gets used for something
> we'll probably end up doing something wrong. So warn when that
> happens.
> 
> FIXME there might be some registers where all 1's is a valid value,
> so ideally we should check the register offset instead...
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_sideband.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_sideband.c b/drivers/gpu/drm/i915/intel_sideband.c
> index 0954f13..c1e56f5 100644
> --- a/drivers/gpu/drm/i915/intel_sideband.c
> +++ b/drivers/gpu/drm/i915/intel_sideband.c
> @@ -182,6 +182,10 @@ u32 vlv_dpio_read(struct drm_i915_private *dev_priv, enum pipe pipe, int reg)
>  
>  	vlv_sideband_rw(dev_priv, DPIO_DEVFN, DPIO_PHY_IOSF_PORT(DPIO_PHY(pipe)),
>  			DPIO_OPCODE_REG_READ, reg, &val);
> +
> +	WARN(val == 0xffffffff, "DPIO read pipe %c reg 0x%x == 0x%x\n",
> +	     pipe_name(pipe), reg, val);
> +
>  	return val;
>  }
>  

Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center