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

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Message-ID: <20260206200529.10784-1-git@danielhodges.dev>
Date: Fri,  6 Feb 2026 15:05:29 -0500
From: Daniel Hodges <git@...ielhodges.dev>
To: mani@...nel.org,
	kwilczynski@...nel.org
Cc: kishon@...nel.org,
	bhelgaas@...gle.com,
	mhi@...ts.linux.dev,
	linux-arm-msm@...r.kernel.org,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org,
	Daniel Hodges <git@...ielhodges.dev>
Subject: [PATCH] PCI: epf-mhi: return 0 on success instead of positive jiffies

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@...r.kernel.org
Signed-off-by: Daniel Hodges <git@...ielhodges.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