linux-kernel - [PATCH v2 3/3] drm/v3d: Make sure the GPU is on when measuring clocks.

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Date:   Tue, 12 Feb 2019 12:27:13 -0800
From:   Eric Anholt <eric@...olt.net>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, david.emett@...adcom.com,
        thomas.spurden@...adcom.com, Eric Anholt <eric@...olt.net>
Subject: [PATCH v2 3/3] drm/v3d: Make sure the GPU is on when measuring clocks.

You'll get garbage measurements if the registers always read back
0xdeadbeef

Signed-off-by: Eric Anholt <eric@...olt.net>
---
 drivers/gpu/drm/v3d/v3d_debugfs.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/v3d/v3d_debugfs.c b/drivers/gpu/drm/v3d/v3d_debugfs.c
index eb2b2d2f8553..a24af2d2f574 100644
--- a/drivers/gpu/drm/v3d/v3d_debugfs.c
+++ b/drivers/gpu/drm/v3d/v3d_debugfs.c
@@ -187,6 +187,11 @@ static int v3d_measure_clock(struct seq_file *m, void *unused)
 	uint32_t cycles;
 	int core = 0;
 	int measure_ms = 1000;
+	int ret;
+
+	ret = pm_runtime_get_sync(v3d->dev);
+	if (ret < 0)
+		return ret;
 
 	if (v3d->ver >= 40) {
 		V3D_CORE_WRITE(core, V3D_V4_PCTR_0_SRC_0_3,
@@ -210,6 +215,9 @@ static int v3d_measure_clock(struct seq_file *m, void *unused)
 		   cycles / (measure_ms * 1000),
 		   (cycles / (measure_ms * 100)) % 10);
 
+	pm_runtime_mark_last_busy(v3d->dev);
+	pm_runtime_put_autosuspend(v3d->dev);
+
 	return 0;
 }
 
-- 
2.20.1