linux-kernel - Re: [PATCH v2 2/3] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race"

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Date:   Mon, 26 Oct 2020 10:05:00 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Wolfram Sang <wsa@...nel.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Akash Asthana <akashast@...eaurora.org>,
        linux-i2c@...r.kernel.org,
        Roja Rani Yarubandi <rojay@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        linux-arm-msm@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Mukesh Savaliya <msavaliy@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race"

On Tue 13 Oct 16:25 CDT 2020, Douglas Anderson wrote:

> 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>

Wolfram, would you like to pick this patch or would you prefer that it
goes together with the other two through the soc tree?

Per Doug's description it has a functional dependency on patch 1, but as
long as all three patches makes it into v5.11 I'm okay with either way.

Regards,
Bjorn

> ---
> 
> (no changes since v1)
> 
>  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
>