Re: [PATCH] dmaengine: qcom: bam_dma: fix runtime PM underflow

From: Caleb Connolly
Date: Tue Jun 28 2022 - 08:08:50 EST




On 16/06/2022 15:00, Vinod Koul wrote:
On 09-06-22, 20:50, Caleb Connolly wrote:
When PM runtime is disabled, pm_runtime_get() isn't called, but
pm_runtime_put() still is. Fix this by creating a matching wrapper
on pm_runtime_put_autosuspend().

Fixes: dbad41e7bb5f ("dmaengine: qcom: bam_dma: check if the runtime pm enabled")
Signed-off-by: Caleb Connolly <caleb.connolly@xxxxxxxxxx>
---
drivers/dma/qcom/bam_dma.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index 87f6ca1541cf..a36dedee262e 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -566,6 +566,14 @@ static int bam_pm_runtime_get_sync(struct device *dev)
return 0;
}
+static int bam_pm_runtime_put_autosuspend(struct device *dev)
+{
+ if (pm_runtime_enabled(dev))
+ return pm_runtime_put_autosuspend(dev);
+
+ return 0;
+}

should we really do a wrapper to fix this ;-) I would think dropping the
get wrapper and calling pm_runtime_get() unconditionally would be
better..?
The original pm_runtime_get() wrapper was added because _get() returns -EACCES if PM is disabled for the device, I've read through some of the pm_runtime docs and I don't see any way to handle this nicely in the framework. I think the real fix will have to be in pm_runtime.

I can rework this to explicitly check for -EACCES on every _get() call, but we still need to check if pm_runtime is enabled before calling _put().

+
/**
* bam_free_chan - Frees dma resources associated with specific channel
* @chan: specified channel
@@ -617,7 +625,7 @@ static void bam_free_chan(struct dma_chan *chan)
err:
pm_runtime_mark_last_busy(bdev->dev);
- pm_runtime_put_autosuspend(bdev->dev);
+ bam_pm_runtime_put_autosuspend(bdev->dev);
}
/**
@@ -793,7 +801,7 @@ static int bam_pause(struct dma_chan *chan)
bchan->paused = 1;
spin_unlock_irqrestore(&bchan->vc.lock, flag);
pm_runtime_mark_last_busy(bdev->dev);
- pm_runtime_put_autosuspend(bdev->dev);
+ bam_pm_runtime_put_autosuspend(bdev->dev);
return 0;
}
@@ -819,7 +827,7 @@ static int bam_resume(struct dma_chan *chan)
bchan->paused = 0;
spin_unlock_irqrestore(&bchan->vc.lock, flag);
pm_runtime_mark_last_busy(bdev->dev);
- pm_runtime_put_autosuspend(bdev->dev);
+ bam_pm_runtime_put_autosuspend(bdev->dev);
return 0;
}
@@ -936,7 +944,7 @@ static irqreturn_t bam_dma_irq(int irq, void *data)
}
pm_runtime_mark_last_busy(bdev->dev);
- pm_runtime_put_autosuspend(bdev->dev);
+ bam_pm_runtime_put_autosuspend(bdev->dev);
return IRQ_HANDLED;
}
@@ -1111,7 +1119,7 @@ static void bam_start_dma(struct bam_chan *bchan)
bam_addr(bdev, bchan->id, BAM_P_EVNT_REG));
pm_runtime_mark_last_busy(bdev->dev);
- pm_runtime_put_autosuspend(bdev->dev);
+ bam_pm_runtime_put_autosuspend(bdev->dev);
}
/**
--
2.36.1


--
Kind Regards,
Caleb (they/he)