linux-kernel - [PATCH v3 9/9] i2c: tegra: Check DMA completion status in addition to left time

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Message-Id: <20200106010423.5890-10-digetx@gmail.com>
Date:   Mon,  6 Jan 2020 04:04:23 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Mikko Perttunen <cyndis@...si.fi>,
        Wolfram Sang <wsa@...-dreams.de>
Cc:     linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 9/9] i2c: tegra: Check DMA completion status in addition to left time

It is more robust to check completion status in addition to the left time
in a case of DMA transfer because transfer's completion happens in two
phases [one is ISR, other is tasklet] and thus it is possible that DMA is
completed while I2C completion awaiting times out because of the deferred
notification done by the DMA driver. The DMA completion status becomes
100% actual after DMA synchronization. This fixes spurious DMA timeouts
when system is under load.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/i2c/busses/i2c-tegra.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 3c7c86d4b0e4..cbc2ad49043e 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1224,7 +1224,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 					 i2c_dev->rx_dma_chan :
 					 i2c_dev->tx_dma_chan);
 
-		if (time_left == 0) {
+		if (!time_left && !completion_done(&i2c_dev->dma_complete)) {
 			dev_err(i2c_dev->dev, "DMA transfer timeout\n");
 			tegra_i2c_init(i2c_dev, true);
 			return -ETIMEDOUT;
-- 
2.24.0