[Intel-gfx] [PATCH 2/2] drm/i915: restrict unclaimed register checking

[Chris Wilson]

On Tue, Aug 25, 2015 at 07:03:42PM -0300, Paulo Zanoni wrote:
> The unclaimed register bit is only triggered when someone touches the
> specified register range.
> 
> For the normal use case (with i915.mmio_debug=0), this commit will
> avoid the extra __raw_i915_read32() call for every register outside
> the specified range, at the expense of a few additional "if"
> statements.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>


> @@ -612,7 +614,7 @@ hsw_unclaimed_reg_debug(struct drm_i915_private *dev_priv, u32 reg, bool read,
>  	const char *op = read ? "reading" : "writing to";
>  	const char *when = before ? "before" : "after";
>  
> -	if (!i915.mmio_debug)
> +	if (!i915.mmio_debug || !UNCLAIMED_CHECK_RANGE(reg))
>  		return;

Place the register check on the preceding line so that it is not
confused with checking the debug-enabled status. (Also you can argue
that reg will be register/cache-hot and so a cheaper test to do first
than loading a module parameter.)

>  	if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
> @@ -624,11 +626,11 @@ hsw_unclaimed_reg_debug(struct drm_i915_private *dev_priv, u32 reg, bool read,
>  }
>  
>  static void
> -hsw_unclaimed_reg_detect(struct drm_i915_private *dev_priv)
> +hsw_unclaimed_reg_detect(struct drm_i915_private *dev_priv, u32 reg)
>  {
>  	static bool mmio_debug_once = true;
>  
> -	if (i915.mmio_debug || !mmio_debug_once)
> +	if (i915.mmio_debug || !UNCLAIMED_CHECK_RANGE(reg) || !mmio_debug_once)
>  		return;

The use is wrong here though because you never reviewed my patch to
enable the single-shot debugging from the interrupt handler to catch
invalid usage from elsewhere.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre