[Intel-gfx] [PATCH] drm/i915: Disable the mmio.debug WARN after it fires

[Daniel Vetter]

On Mon, Nov 24, 2014 at 08:12:57AM +0000, Chris Wilson wrote:
> If we have a single unclaimed register, we will have lots. A WARN for
> each one makes the machine unusable and does not aid debugging. Convert
> the i915.mmio_debug option to a counter for how many WARNs to fire
> before shutting up. Even when i915.mmio_debug was disabled it would
> continue to shout an *ERROR* for every interrupt, without any
> information at all for debugging.
> 
> The massive verbiage was added in
> commit 5978118c39c2f72fd8b39ef9c086723542384809
> Author: Paulo Zanoni <paulo.r.zanoni at intel.com>
> Date:   Wed Jul 16 17:49:29 2014 -0300
> 
>     drm/i915: reorganize the unclaimed register detection code
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Rodrigo Vivi <rodrigo.vivi at gmail.com>
> Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h     | 2 +-
>  drivers/gpu/drm/i915/i915_params.c  | 5 ++---
>  drivers/gpu/drm/i915/intel_uncore.c | 6 ++++--
>  3 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 5448ce9d1490..314d8a60d55b 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2310,7 +2310,7 @@ struct i915_params {
>  	bool disable_display;
>  	bool disable_vtd_wa;
>  	int use_mmio_flip;
> -	bool mmio_debug;
> +	int mmio_debug;
>  };
>  extern struct i915_params i915 __read_mostly;
>  
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index c91cb2033cc5..654a492fcfca 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -169,7 +169,6 @@ module_param_named(use_mmio_flip, i915.use_mmio_flip, int, 0600);
>  MODULE_PARM_DESC(use_mmio_flip,
>  		 "use MMIO flips (-1=never, 0=driver discretion [default], 1=always)");
>  
> -module_param_named(mmio_debug, i915.mmio_debug, bool, 0600);
> +module_param_named(mmio_debug, i915.mmio_debug, int, 0600);
>  MODULE_PARM_DESC(mmio_debug,
> -	"Enable the MMIO debug code (default: false). This may negatively "
> -	"affect performance.");
> +	"Enable the MMIO debug code. This may negatively affect performance.");
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index f0230b0e8e11..b830407dc2aa 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -714,25 +714,27 @@ 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 <= 0)
>  		return;
>  
>  	if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
>  		WARN(1, "Unclaimed register detected %s %s register 0x%x\n",
>  		     when, op, reg);
>  		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
> +		i915.mmio_debug--;
>  	}
>  }
>  
>  static void
>  hsw_unclaimed_reg_detect(struct drm_i915_private *dev_priv)
>  {
> -	if (i915.mmio_debug)
> +	if (i915.mmio_debug > 0)
>  		return;
>  
>  	if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
>  		DRM_ERROR("Unclaimed register detected. Please use the i915.mmio_debug=1 to debug this problem.");
>  		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
> +		i915.mmio_debug--;

Why the decrement here? And if we make this fancy, maybe we should have a
oneshot set to enable mmio_debug here, i.e.

static mmio_debug_oneshot = 1;

if (unclaimed_mmio_detected) {
	clear();
	mmio_debug = mmio_debug_oneshot--;
}

Or something similar? That way if it's recurring we'll capture it, but
only once.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch