[PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[Daniel Hodges]

wait_for_completion_timeout() returns the number of jiffies remaining
on success (positive value) or 0 on timeout. The pci_epf_mhi_edma_read()
and pci_epf_mhi_edma_write() functions use the return value directly as
their own return value, only converting timeout (0) to -ETIMEDOUT.

On success, they return the positive jiffies value. The callers in
drivers/bus/mhi/ep/ring.c check for errors with "if (ret < 0)" for
read_sync and "if (ret)" for write_sync. This causes write_sync success
cases to be incorrectly treated as errors since the positive jiffies
value is non-zero.

Fix by setting ret to 0 when wait_for_completion_timeout() succeeds.

Fixes: 7b99aaaddabb ("PCI: epf-mhi: Add eDMA support")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Hodges <git@danielhodges.dev>
---
 drivers/pci/endpoint/functions/pci-epf-mhi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
index 6643a88c7a0c..2f077d0b7957 100644
--- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
+++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
@@ -367,6 +367,8 @@ static int pci_epf_mhi_edma_read(struct mhi_ep_cntrl *mhi_cntrl,
 		dev_err(dev, "DMA transfer timeout\n");
 		dmaengine_terminate_sync(chan);
 		ret = -ETIMEDOUT;
+	} else {
+		ret = 0;
 	}
 
 err_unmap:
@@ -438,6 +440,8 @@ static int pci_epf_mhi_edma_write(struct mhi_ep_cntrl *mhi_cntrl,
 		dev_err(dev, "DMA transfer timeout\n");
 		dmaengine_terminate_sync(chan);
 		ret = -ETIMEDOUT;
+	} else {
+		ret = 0;
 	}
 
 err_unmap:
-- 
2.52.0

Re: [PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[Krishna Chaitanya Chundru]

On 2/7/2026 1:35 AM, Daniel Hodges wrote:
> wait_for_completion_timeout() returns the number of jiffies remaining
> on success (positive value) or 0 on timeout. The pci_epf_mhi_edma_read()
> and pci_epf_mhi_edma_write() functions use the return value directly as
> their own return value, only converting timeout (0) to -ETIMEDOUT.
>
> On success, they return the positive jiffies value. The callers in
> drivers/bus/mhi/ep/ring.c check for errors with "if (ret < 0)" for
> read_sync and "if (ret)" for write_sync. This causes write_sync success
> cases to be incorrectly treated as errors since the positive jiffies
> value is non-zero.
>
> Fix by setting ret to 0 when wait_for_completion_timeout() succeeds.
>
> Fixes: 7b99aaaddabb ("PCI: epf-mhi: Add eDMA support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Hodges <git@danielhodges.dev>

Reviewed-by: Krishna Chaitanya Chundru<krishna.chundru@oss.qualcomm.com>

- Krishna Chaitanya.

> ---
>   drivers/pci/endpoint/functions/pci-epf-mhi.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> index 6643a88c7a0c..2f077d0b7957 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> @@ -367,6 +367,8 @@ static int pci_epf_mhi_edma_read(struct mhi_ep_cntrl *mhi_cntrl,
>   		dev_err(dev, "DMA transfer timeout\n");
>   		dmaengine_terminate_sync(chan);
>   		ret = -ETIMEDOUT;
> +	} else {
> +		ret = 0;
>   	}
>   
>   err_unmap:
> @@ -438,6 +440,8 @@ static int pci_epf_mhi_edma_write(struct mhi_ep_cntrl *mhi_cntrl,
>   		dev_err(dev, "DMA transfer timeout\n");
>   		dmaengine_terminate_sync(chan);
>   		ret = -ETIMEDOUT;
> +	} else {
> +		ret = 0;
>   	}
>   
>   err_unmap:

Re: [PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[Manivannan Sadhasivam]

On Fri, 06 Feb 2026 15:05:29 -0500, Daniel Hodges wrote:
> wait_for_completion_timeout() returns the number of jiffies remaining
> on success (positive value) or 0 on timeout. The pci_epf_mhi_edma_read()
> and pci_epf_mhi_edma_write() functions use the return value directly as
> their own return value, only converting timeout (0) to -ETIMEDOUT.
> 
> On success, they return the positive jiffies value. The callers in
> drivers/bus/mhi/ep/ring.c check for errors with "if (ret < 0)" for
> read_sync and "if (ret)" for write_sync. This causes write_sync success
> cases to be incorrectly treated as errors since the positive jiffies
> value is non-zero.
> 
> [...]

Applied, thanks!

[1/1] PCI: epf-mhi: return 0 on success instead of positive jiffies
      commit: f6797680fe312ae6d32a773eb4d33400f24555c2

Best regards,
-- 
Manivannan Sadhasivam <mani@kernel.org>

Re: [PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[Bjorn Helgaas]

On Fri, Feb 06, 2026 at 03:05:29PM -0500, Daniel Hodges wrote:
> wait_for_completion_timeout() returns the number of jiffies remaining
> on success (positive value) or 0 on timeout. The pci_epf_mhi_edma_read()
> and pci_epf_mhi_edma_write() functions use the return value directly as
> their own return value, only converting timeout (0) to -ETIMEDOUT.
> 
> On success, they return the positive jiffies value. The callers in
> drivers/bus/mhi/ep/ring.c check for errors with "if (ret < 0)" for
> read_sync and "if (ret)" for write_sync. This causes write_sync success
> cases to be incorrectly treated as errors since the positive jiffies
> value is non-zero.
> 
> Fix by setting ret to 0 when wait_for_completion_timeout() succeeds.
> 
> Fixes: 7b99aaaddabb ("PCI: epf-mhi: Add eDMA support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Hodges <git@danielhodges.dev>

Thanks for the patch!

Two questions: first, is there any reason why __mhi_ep_cache_ring()
tests for "ret < 0" but mhi_ep_ring_add_element() tests for "ret"
(non-zero)?  Could/should they both test just for non-zero, which I
think is the typical style?

Second, the subject and commit log are perfectly correct but basically
at the level of describing the C code.  I propose something along
these lines:

  PCI: epf-mhi: Return 0, not remaining timeout, when eDMA ops complete

  pci_epf_mhi_edma_read() and pci_epf_mhi_edma_write() start DMA
  operations and wait for completion with a timeout.

  On successful completion, they previously returned the remaining
  timeout, which callers may treat as an error.  In particular,
  mhi_ep_ring_add_element(), which calls pci_epf_mhi_edma_write() via
  mhi_cntrl->write_sync(), interprets any non-zero return value as
  failure.

  Return 0 on success instead of the remaining timeout to prevent
  mhi_ep_ring_add_element() from treating successful completion as an
  error.

> ---
>  drivers/pci/endpoint/functions/pci-epf-mhi.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> index 6643a88c7a0c..2f077d0b7957 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> @@ -367,6 +367,8 @@ static int pci_epf_mhi_edma_read(struct mhi_ep_cntrl *mhi_cntrl,
>  		dev_err(dev, "DMA transfer timeout\n");
>  		dmaengine_terminate_sync(chan);
>  		ret = -ETIMEDOUT;
> +	} else {
> +		ret = 0;
>  	}
>  
>  err_unmap:
> @@ -438,6 +440,8 @@ static int pci_epf_mhi_edma_write(struct mhi_ep_cntrl *mhi_cntrl,
>  		dev_err(dev, "DMA transfer timeout\n");
>  		dmaengine_terminate_sync(chan);
>  		ret = -ETIMEDOUT;
> +	} else {
> +		ret = 0;
>  	}
>  
>  err_unmap:
> -- 
> 2.52.0
> 

Re: [PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[Manivannan Sadhasivam]

On Fri, Feb 27, 2026 at 01:15:10PM -0600, Bjorn Helgaas wrote:
> On Fri, Feb 06, 2026 at 03:05:29PM -0500, Daniel Hodges wrote:
> > wait_for_completion_timeout() returns the number of jiffies remaining
> > on success (positive value) or 0 on timeout. The pci_epf_mhi_edma_read()
> > and pci_epf_mhi_edma_write() functions use the return value directly as
> > their own return value, only converting timeout (0) to -ETIMEDOUT.
> > 
> > On success, they return the positive jiffies value. The callers in
> > drivers/bus/mhi/ep/ring.c check for errors with "if (ret < 0)" for
> > read_sync and "if (ret)" for write_sync. This causes write_sync success
> > cases to be incorrectly treated as errors since the positive jiffies
> > value is non-zero.
> > 
> > Fix by setting ret to 0 when wait_for_completion_timeout() succeeds.
> > 
> > Fixes: 7b99aaaddabb ("PCI: epf-mhi: Add eDMA support")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Daniel Hodges <git@danielhodges.dev>
> 
> Thanks for the patch!
> 
> Two questions: first, is there any reason why __mhi_ep_cache_ring()
> tests for "ret < 0" but mhi_ep_ring_add_element() tests for "ret"
> (non-zero)?  Could/should they both test just for non-zero, which I
> think is the typical style?
> 

Yes, agree. I've sent a patch to fix this. Thanks for spotting!

> Second, the subject and commit log are perfectly correct but basically
> at the level of describing the C code.  I propose something along
> these lines:
> 
>   PCI: epf-mhi: Return 0, not remaining timeout, when eDMA ops complete
> 
>   pci_epf_mhi_edma_read() and pci_epf_mhi_edma_write() start DMA
>   operations and wait for completion with a timeout.
> 
>   On successful completion, they previously returned the remaining
>   timeout, which callers may treat as an error.  In particular,
>   mhi_ep_ring_add_element(), which calls pci_epf_mhi_edma_write() via
>   mhi_cntrl->write_sync(), interprets any non-zero return value as
>   failure.
> 
>   Return 0 on success instead of the remaining timeout to prevent
>   mhi_ep_ring_add_element() from treating successful completion as an
>   error.
> 

Ammended the commit with the above, thanks!

- Mani

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

[Daniel Hodges]

On Mon, Mar 02, 2026 at 11:24:23AM +0530, Manivannan Sadhasivam wrote:
> On Fri, Feb 27, 2026 at 01:15:10PM -0600, Bjorn Helgaas wrote:
> > On Fri, Feb 06, 2026 at 03:05:29PM -0500, Daniel Hodges wrote:
> > > wait_for_completion_timeout() returns the number of jiffies remaining
> > > on success (positive value) or 0 on timeout. The pci_epf_mhi_edma_read()
> > > and pci_epf_mhi_edma_write() functions use the return value directly as
> > > their own return value, only converting timeout (0) to -ETIMEDOUT.
> > > 
> > > On success, they return the positive jiffies value. The callers in
> > > drivers/bus/mhi/ep/ring.c check for errors with "if (ret < 0)" for
> > > read_sync and "if (ret)" for write_sync. This causes write_sync success
> > > cases to be incorrectly treated as errors since the positive jiffies
> > > value is non-zero.
> > > 
> > > Fix by setting ret to 0 when wait_for_completion_timeout() succeeds.
> > > 
> > > Fixes: 7b99aaaddabb ("PCI: epf-mhi: Add eDMA support")
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Daniel Hodges <git@danielhodges.dev>
> > 
> > Thanks for the patch!
> > 
> > Two questions: first, is there any reason why __mhi_ep_cache_ring()
> > tests for "ret < 0" but mhi_ep_ring_add_element() tests for "ret"
> > (non-zero)?  Could/should they both test just for non-zero, which I
> > think is the typical style?
> > 
> 
> Yes, agree. I've sent a patch to fix this. Thanks for spotting!
> 
> > Second, the subject and commit log are perfectly correct but basically
> > at the level of describing the C code.  I propose something along
> > these lines:
> > 
> >   PCI: epf-mhi: Return 0, not remaining timeout, when eDMA ops complete
> > 
> >   pci_epf_mhi_edma_read() and pci_epf_mhi_edma_write() start DMA
> >   operations and wait for completion with a timeout.
> > 
> >   On successful completion, they previously returned the remaining
> >   timeout, which callers may treat as an error.  In particular,
> >   mhi_ep_ring_add_element(), which calls pci_epf_mhi_edma_write() via
> >   mhi_cntrl->write_sync(), interprets any non-zero return value as
> >   failure.
> > 
> >   Return 0 on success instead of the remaining timeout to prevent
> >   mhi_ep_ring_add_element() from treating successful completion as an
> >   error.
> > 
> 
> Ammended the commit with the above, thanks!
> 
> - Mani

Thanks for cleaning up! I meant to get around to this, but got a little
distracted with some other things.

-Daniel