linux-kernel - [PATCH 2/3] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race"

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Message-Id: <20201008155154.2.I7b22281453b8a18ab16ef2bfd4c641fb1cc6a92c@changeid>
Date:   Thu,  8 Oct 2020 15:52:34 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Wolfram Sang <wsa@...nel.org>,
        Akash Asthana <akashast@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        linux-i2c@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Mukesh Savaliya <msavaliy@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race"

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>
---

 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 dead5db3315a..32b2a9921b14 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -367,6 +367,7 @@ 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);
@@ -374,8 +375,6 @@ 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);
@@ -409,6 +408,7 @@ 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);
@@ -416,8 +416,6 @@ 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);
 
-- 
2.28.0.1011.ga647a8990f-goog