On 2021-04-27 11:27, Mauro Carvalho Chehab wrote:
Despite other *_get()/*_put() functions, where usage count is
incremented only if not errors, the pm_runtime_get_sync() has
a different behavior, incrementing the counter *even* on
errors.
That's an error prone behavior, as people often forget to
decrement the usage counter.
However, the hantro driver depends on this behavior, as it
will decrement the usage_count unconditionally at the m2m
job finish time, which makes sense.
So, intead of using the pm_runtime_resume_and_get() that
would decrement the counter on error, keep the current
API, but add a documentation explaining the rationale for
keep using pm_runtime_get_sync().
Signed-off-by: Mauro Carvalho Chehab <mchehab+hua...@kernel.org>
---
drivers/staging/media/hantro/hantro_drv.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/staging/media/hantro/hantro_drv.c
b/drivers/staging/media/hantro/hantro_drv.c
index 595e82a82728..96f940c1c85c 100644
--- a/drivers/staging/media/hantro/hantro_drv.c
+++ b/drivers/staging/media/hantro/hantro_drv.c
@@ -155,6 +155,13 @@ static void device_run(void *priv)
ret = clk_bulk_enable(ctx->dev->variant->num_clocks, ctx->dev->clocks);
if (ret)
goto err_cancel_job;
..except this can also cause the same pm_runtime_put_autosuspend() call
without even reaching the "matching" get below, so rather than some kind
of cleverness it seems more like it's just broken :/
Robin.
+
+ /*
+ * The pm_runtime_get_sync() will increment dev->power.usage_count,
+ * even on errors. That's the expected behavior here, since the
+ * hantro_job_finish() function at the error handling code
+ * will internally call pm_runtime_put_autosuspend().
+ */
ret = pm_runtime_get_sync(ctx->dev->dev);
if (ret < 0)
goto err_cancel_job;
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