[Intel-gfx] [PATCH 1/3] drm/i915: Keep the ctx workarounds tightly packed

[Oscar Mateo Lozano]

On 6/15/2018 1:59 AM, Chris Wilson wrote:
> For each platform, we have a few registers that rewritten with multiple
> values -- they are not part of a sequence, just different parts of a
> masked register set at different times (e.g. platform and gen
> workarounds). Consolidate these into a single register write to keep the
> table compact.
>
> While adjusting the construction of the wa table, make it non fatal so
> that the driver still loads but keeping the warning and extra details
> for inspection.

A while ago I sent a patch 
(https://patchwork.freedesktop.org/patch/205035/) that uses simple MMIO 
writes to apply ctx workarounds. This is possible since we now have 
proper golden contexts, and avoids the need for these patches.
It also has the advantage that an improperly classified WA doesn't get 
lost (we still need the classification if we want to properly validate 
the WAs, but that's a different story).
Are we sure we prefer to do this instead?

>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Oscar Mateo <oscar.mateo at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_debugfs.c      | 25 ++--------
>   drivers/gpu/drm/i915/i915_drv.h          |  2 +-
>   drivers/gpu/drm/i915/intel_workarounds.c | 63 +++++++++++++++++-------
>   3 files changed, 52 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index c600279d3db5..f78895ffab9b 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -3378,28 +3378,13 @@ static int i915_shared_dplls_info(struct seq_file *m, void *unused)
>   
>   static int i915_wa_registers(struct seq_file *m, void *unused)
>   {
> -	struct drm_i915_private *dev_priv = node_to_i915(m->private);
> -	struct i915_workarounds *workarounds = &dev_priv->workarounds;
> +	struct i915_workarounds *wa = &node_to_i915(m->private)->workarounds;
>   	int i;
>   
> -	intel_runtime_pm_get(dev_priv);
> -
> -	seq_printf(m, "Workarounds applied: %d\n", workarounds->count);
> -	for (i = 0; i < workarounds->count; ++i) {
> -		i915_reg_t addr;
> -		u32 mask, value, read;
> -		bool ok;
> -
> -		addr = workarounds->reg[i].addr;
> -		mask = workarounds->reg[i].mask;
> -		value = workarounds->reg[i].value;
> -		read = I915_READ(addr);
> -		ok = (value & mask) == (read & mask);
> -		seq_printf(m, "0x%X: 0x%08X, mask: 0x%08X, read: 0x%08x, status: %s\n",
> -			   i915_mmio_reg_offset(addr), value, mask, read, ok ? "OK" : "FAIL");
> -	}
> -
> -	intel_runtime_pm_put(dev_priv);
> +	seq_printf(m, "Workarounds applied: %d\n", wa->count);
> +	for (i = 0; i < wa->count; ++i)
> +		seq_printf(m, "0x%X: 0x%08X, mask: 0x%08X\n",
> +			   wa->reg[i].addr, wa->reg[i].value, wa->reg[i].mask);
>   
>   	return 0;
>   }
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 2c12de678e32..91c389622217 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1308,7 +1308,7 @@ struct i915_frontbuffer_tracking {
>   };
>   
>   struct i915_wa_reg {
> -	i915_reg_t addr;
> +	u32 addr;
>   	u32 value;
>   	/* bitmask representing WA bits */
>   	u32 mask;
> diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
> index 24b929ce3341..f8bb32e974f6 100644
> --- a/drivers/gpu/drm/i915/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/intel_workarounds.c
> @@ -48,29 +48,58 @@
>    * - Public functions to init or apply the given workaround type.
>    */
>   
> -static int wa_add(struct drm_i915_private *dev_priv,
> -		  i915_reg_t addr,
> -		  const u32 mask, const u32 val)
> +static void wa_add(struct drm_i915_private *i915,
> +		   i915_reg_t reg, const u32 mask, const u32 val)
>   {
> -	const unsigned int idx = dev_priv->workarounds.count;
> +	struct i915_workarounds *wa = &i915->workarounds;
> +	unsigned int start = 0, end = wa->count;
> +	unsigned int addr = i915_mmio_reg_offset(reg);
> +	struct i915_wa_reg *r;
> +
> +	while (start < end) {
> +		unsigned int mid = start + (end - start) / 2;
> +
> +		if (wa->reg[mid].addr < addr) {
> +			start = mid + 1;
> +		} else if (wa->reg[mid].addr > addr) {
> +			end = mid;
> +		} else {
> +			r = &wa->reg[mid];
> +
> +			if ((mask & ~r->mask) == 0) {
> +				DRM_ERROR("Discarding overwritten w/a for reg %04x (mask: %08x, value: %08x)\n",
> +					  addr, r->mask, r->value);
> +
> +				r->value &= ~mask;
> +			}
> +
> +			r->value |= val;
> +			r->mask  |= mask;
> +			return;
> +		}
> +	}
>   
> -	if (WARN_ON(idx >= I915_MAX_WA_REGS))
> -		return -ENOSPC;
> +	if (WARN_ON_ONCE(wa->count >= I915_MAX_WA_REGS)) {
> +		DRM_ERROR("Dropping w/a for reg %04x (mask: %08x, value: %08x)\n",
> +			  addr, mask, val);
> +		return;
> +	}
>   
> -	dev_priv->workarounds.reg[idx].addr = addr;
> -	dev_priv->workarounds.reg[idx].value = val;
> -	dev_priv->workarounds.reg[idx].mask = mask;
> +	r = &wa->reg[wa->count++];
> +	r->addr  = addr;
> +	r->value = val;
> +	r->mask  = mask;
>   
> -	dev_priv->workarounds.count++;
> +	while (r-- > wa->reg) {
> +		GEM_BUG_ON(r[0].addr == r[1].addr);
> +		if (r[1].addr > r[0].addr)
> +			break;
>   
> -	return 0;
> +		swap(r[1], r[0]);
> +	}
>   }
>   
> -#define WA_REG(addr, mask, val) do { \
> -		const int r = wa_add(dev_priv, (addr), (mask), (val)); \
> -		if (r) \
> -			return r; \
> -	} while (0)
> +#define WA_REG(addr, mask, val) wa_add(dev_priv, (addr), (mask), (val))
>   
>   #define WA_SET_BIT_MASKED(addr, mask) \
>   	WA_REG(addr, (mask), _MASKED_BIT_ENABLE(mask))
> @@ -540,7 +569,7 @@ int intel_ctx_workarounds_emit(struct i915_request *rq)
>   
>   	*cs++ = MI_LOAD_REGISTER_IMM(w->count);
>   	for (i = 0; i < w->count; i++) {
> -		*cs++ = i915_mmio_reg_offset(w->reg[i].addr);
> +		*cs++ = w->reg[i].addr;
>   		*cs++ = w->reg[i].value;
>   	}
>   	*cs++ = MI_NOOP;