linux-kernel - [PATCH 5.4 082/453] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race"

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Date:   Mon, 28 Dec 2020 13:45:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Douglas Anderson <dianders@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Akash Asthana <akashast@...eaurora.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 082/453] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race"

From: Douglas Anderson <dianders@...omium.org>

[ Upstream commit 9cb4c67d7717135d6f4600a49ab07b470ea4ee2f ]

This reverts commit 02b9aec59243c6240fc42884acc958602146ddf6.

As talked about in the patch ("soc: qcom: geni: More properly switch
to DMA mode"), swapping the order of geni_se_setup_m_cmd() and
geni_se_xx_dma_prep() can sometimes cause corrupted transfers.  Thus
we traded one problem for another.  Now that we've debugged the
problem further and fixed the geni helper functions to more disable
FIFO interrupts when we move to DMA mode we can revert it and end up
with (hopefully) zero problems!

To be explicit, the patch ("soc: qcom: geni: More properly switch
to DMA mode") is a prerequisite for this one.

Fixes: 02b9aec59243 ("i2c: i2c-qcom-geni: Fix DMA transfer race")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Reviewed-by: Akash Asthana <akashast@...eaurora.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Link: https://lore.kernel.org/r/20201013142448.v2.2.I7b22281453b8a18ab16ef2bfd4c641fb1cc6a92c@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/i2c/busses/i2c-qcom-geni.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index aafc76ee93e02..17abf60c94aeb 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -368,6 +368,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		geni_se_select_mode(se, GENI_SE_FIFO);
 
 	writel_relaxed(len, se->base + SE_I2C_RX_TRANS_LEN);
+	geni_se_setup_m_cmd(se, I2C_READ, m_param);
 
 	if (dma_buf && geni_se_rx_dma_prep(se, dma_buf, len, &rx_dma)) {
 		geni_se_select_mode(se, GENI_SE_FIFO);
@@ -375,8 +376,6 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		dma_buf = NULL;
 	}
 
-	geni_se_setup_m_cmd(se, I2C_READ, m_param);
-
 	time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
 	if (!time_left)
 		geni_i2c_abort_xfer(gi2c);
@@ -410,6 +409,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		geni_se_select_mode(se, GENI_SE_FIFO);
 
 	writel_relaxed(len, se->base + SE_I2C_TX_TRANS_LEN);
+	geni_se_setup_m_cmd(se, I2C_WRITE, m_param);
 
 	if (dma_buf && geni_se_tx_dma_prep(se, dma_buf, len, &tx_dma)) {
 		geni_se_select_mode(se, GENI_SE_FIFO);
@@ -417,8 +417,6 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		dma_buf = NULL;
 	}
 
-	geni_se_setup_m_cmd(se, I2C_WRITE, m_param);
-
 	if (!dma_buf) /* Get FIFO IRQ */
 		writel_relaxed(1, se->base + SE_GENI_TX_WATERMARK_REG);
 
-- 
2.27.0