Re: [PATCH 1/5] drm/i915/guc: doorbell reset should avoid used doorbells

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 19/07/16 13:59, Dave Gordon wrote:
> guc_init_doorbell_hw() borrows the (currently single) GuC client to use
> in reinitialising ALL the doorbell registers (as the hardware doesn't
> reset them when the GuC is reset). As a prerequisite for accommodating
> multiple clients, it should only reset doorbells that are supposed to be
> disabled, avoiding those that are marked as in use by any client.
>
> Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_guc_submission.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 2112e02..d8402e4 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -699,7 +699,7 @@ static void gem_release_guc_obj(struct drm_i915_gem_object *obj)
>   }
>
>   /*
> - * Borrow the first client to set up & tear down every doorbell
> + * Borrow the first client to set up & tear down each unused doorbell
>    * in turn, to ensure that all doorbell h/w is (re)initialised.
>    */
>   static void guc_init_doorbell_hw(struct intel_guc *guc)
> @@ -715,6 +715,9 @@ static void guc_init_doorbell_hw(struct intel_guc *guc)
>   		i915_reg_t drbreg = GEN8_DRBREGL(i);
>   		u32 value = I915_READ(drbreg);
>
> +		if (test_bit(i, guc->doorbell_bitmap))
> +			continue;
> +
>   		err = guc_update_doorbell_id(guc, client, i);
>
>   		/* Report update failure or unexpectedly active doorbell */
> @@ -733,6 +736,9 @@ static void guc_init_doorbell_hw(struct intel_guc *guc)
>   		i915_reg_t drbreg = GEN8_DRBREGL(i);
>   		u32 value = I915_READ(drbreg);
>
> +		if (test_bit(i, guc->doorbell_bitmap))
> +			continue;
> +
>   		if (i != db_id && (value & GUC_DOORBELL_ENABLED))
>   			DRM_DEBUG_DRIVER("Doorbell %d (reg 0x%x) finally 0x%x\n",
>   					  i, drbreg.reg, value);
>

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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