On Tue, Apr 25, 2017 at 10:30:07AM -0700, Lionel Landwerlin wrote:
> +static int gen8_configure_all_contexts(struct drm_i915_private *dev_priv)
> +{
> + struct i915_gem_context *ctx;
> + int ret;
> +
> + ret = i915_mutex_lock_interruptible(&dev_priv->drm);
> + if (ret)
> + return ret;
> +
> + /* Switch away from any user context. */
> + ret = i915_gem_switch_to_kernel_context(dev_priv);
> + if (ret) {
> + mutex_unlock(&dev_priv->drm.struct_mutex);
> + return ret;
> + }
> +
> + /* The OA register config is setup through the context image. This image
> + * might be written to by the GPU on context switch (in particular on
> + * lite-restore). This means we can't safely update a context's image,
> + * if this context is scheduled/submitted to run on the GPU.
> + *
> + * We could emit the OA register config through the batch buffer but
> + * this might leave small interval of time where the OA unit is
> + * configured at an invalid sampling period.
> + *
> + * So far the best way to work around this issue seems to be draining
> + * the GPU from any submitted work.
> + */
> + ret = i915_gem_wait_for_idle(dev_priv,
> + I915_WAIT_INTERRUPTIBLE |
> + I915_WAIT_LOCKED);
> + if (ret) {
> + mutex_unlock(&dev_priv->drm.struct_mutex);
> + return ret;
> + }
> +
> + /* Update all contexts now that we've stalled the submission. */
> + list_for_each_entry(ctx, &dev_priv->context_list, link) {
> + if (!ctx->engine[RCS].initialised)
> + continue;
> +
You need to pin the context here, otherwise there is not guarrantee that
the lrc_reg_state exists, or map it directly.
> + gen8_update_reg_state_unlocked(ctx,
> + ctx->engine[RCS].lrc_reg_state);
> + }
> +
> + mutex_unlock(&dev_priv->drm.struct_mutex);
> +
> + /* Now update the current context.
You don't need to. The current context is the kernel context, it is
scratch and never used by userspace so no oa-reports.
> + *
> + * Note: Using MMIO to update per-context registers requires
> + * some extra care...
> + */
> + ret = gen8_begin_ctx_mmio(dev_priv);
> + if (ret) {
> + DRM_ERROR("Failed to bring RCS out of idle to update current
> ctx OA state\n");
> + return ret;
> + }
> +
> + I915_WRITE(GEN8_OACTXCONTROL, ((dev_priv->perf.oa.period_exponent <<
> + GEN8_OA_TIMER_PERIOD_SHIFT) |
> + (dev_priv->perf.oa.periodic ?
> + GEN8_OA_TIMER_ENABLE : 0) |
> + GEN8_OA_COUNTER_RESUME));
> +
> + config_oa_regs(dev_priv, dev_priv->perf.oa.flex_regs,
> + dev_priv->perf.oa.flex_regs_len);
> +
> + gen8_end_ctx_mmio(dev_priv);
This entire chunk can go and I don't need to critique
gen8_begin_ctx_mmio() -- it needs a bit of tlc.
This patch is not ready.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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