Re: [PATCH 1/1] drm/i915: Reset request handling for gen9+

From: Chris Wilson <chris@chris-wilson.co.uk>
To: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 1/1] drm/i915: Reset request handling for gen9+
Date: Tue, 16 Jun 2015 15:09:37 +0100	[thread overview]
Message-ID: <20150616140937.GG11933@nuc-i3427.alporthouse.com> (raw)
In-Reply-To: <1434461963-2438-1-git-send-email-mika.kuoppala@intel.com>

On Tue, Jun 16, 2015 at 04:39:23PM +0300, Mika Kuoppala wrote:
> In order for skl+ hardware to guarantee that no context switch
> takes place during reset and that current context is properly
> saved, the driver needs to notify and query hw before commencing
> with reset.
> 
> We will only proceed with reset if all engines report that they
> are ready for reset.
> 
> As we skip the reset if any single engine reports not ready, this
> commit prevents system hang skl in some situations where the
> gpu/blitter is hanged and in such state that any write to generic
> reset register (GEN6_GDRST) causes immediate system hang.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=89959
> References: https://bugs.freedesktop.org/show_bug.cgi?id=90854
> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h     |  3 +++
>  drivers/gpu/drm/i915/intel_uncore.c | 32 +++++++++++++++++++++++++++++++-
>  2 files changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 0b979ad..3684f92 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1461,6 +1461,9 @@ enum skl_disp_power_wells {
>  #define RING_MAX_IDLE(base)	((base)+0x54)
>  #define RING_HWS_PGA(base)	((base)+0x80)
>  #define RING_HWS_PGA_GEN6(base)	((base)+0x2080)
> +#define RING_RESET_CTL(base)	((base)+0xd0)
> +#define   RESET_CTL_REQUEST_RESET  (1 << 0)
> +#define   RESET_CTL_READY_TO_RESET (1 << 1)
>  
>  #define HSW_GTT_CACHE_EN	0x4024
>  #define   GTT_CACHE_EN_ALL	0xF0007FFF
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 4a86cf0..404bce2 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -1455,9 +1455,39 @@ static int gen6_do_reset(struct drm_device *dev)
>  	return ret;
>  }
>  
> +static int wait_for_bits_set(struct drm_i915_private *dev_priv,
> +			     const u32 reg, const u32 mask, const int timeout)

Use whitespace to group terms, and probably best to call it with both
mask and value for generality.

static int wait_for_register(struct drm_i915_private *dev_priv,
			     const u32 reg,
			     const u32 mask,
			     const u32 value,
			     const unsigend long timeout);

I hope this proves useful elsewhere, do you have a followup patch? It
should reduce the size of our module quite considerably.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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