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

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Mar 31, 2014 at 06:21:27PM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@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...

FIXMEs like this look better in the code, I've pasted it there, too.
-Daniel

> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@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;
>  }
>  
> -- 
> 1.8.3.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch