Re: [PATCH] drm/i915/guc: Skip suspend/resume GuC action on platforms w/o GuC submission

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On Mon, 28 Oct 2019 22:25:27 +0100, <don.hiatt@xxxxxxxxx> wrote:

From: Don Hiatt <don.hiatt@xxxxxxxxx>

On some platforms (e.g. KBL) that do not support GuC submission, but
the user enabled the GuC communication (e.g for HuC authentication)
calling the GuC EXIT_S_STATE action results in lose of ability to
enter RC6. We can remove the GuC suspend/remove entirely as we do
not need to save the GuC submission status.

v2: Do not suspend/resume the GuC on platforms that do not support
    Guc Submission.

Signed-off-by: Don Hiatt <don.hiatt@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/uc/intel_uc.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
index 3fdbc935d155..04031564f0b1 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
@@ -572,10 +572,19 @@ void intel_uc_runtime_suspend(struct intel_uc *uc)
 	if (!intel_guc_is_running(guc))
 		return;
+	/*
+	 * If GuC communciation is enabled but submission is not supported,

typo

+	 * we do not need to suspend the GuC but we do need to disable the
+	 * GuC communication on suspend.
+	 */
+	if (!guc->submission_supported)

Using submission_supported flag directly can be tricky, as today it
is always set to false, but in the future it may indicate either that
submission is supported by the driver/fw and/or enabled by modparam.

There is no guarantee that it will reflect actual runtime status,
as even supported/unblocked guc submission may fallback to execlists.

We may need something like intel_guc_submission_is_active() that will
reflect actual mode of submission currently used by the driver.

+		goto guc_disable_comm;

and maybe we can move above logic to intel_guc_suspend()
to do not introduce extra goto's ?

+
 	err = intel_guc_suspend(guc);
 	if (err)
 		DRM_DEBUG_DRIVER("Failed to suspend GuC, err=%d", err);
+guc_disable_comm:
 	guc_disable_communication(guc);
 }
@@ -605,6 +614,14 @@ static int __uc_resume(struct intel_uc *uc, bool enable_communication)
 	if (enable_communication)
 		guc_enable_communication(guc);
+	/*
+	 * If GuC communciation is enabled but submission is not supported,

typo

+	 * we do not need to resume the GuC but we do need to enable the
+	 * GuC communication on resume (above).
+	 */
+	if (!guc->submission_supported)
+		return 0;

see suspend case comment

+
 	err = intel_guc_resume(guc);
 	if (err) {
 		DRM_DEBUG_DRIVER("Failed to resume GuC, err=%d", err);

Thanks,
Michal
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