linux-kernel - Re: [PATCH] i2c: qcom-geni: Fix GPI DMA buffer sync-back

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Date:   Mon, 08 Aug 2022 08:59:59 +0200
From:   "Luca Weiss" <luca.weiss@...rphone.com>
To:     "Robin Reckmann" <robin.reckmann@...glemail.com>,
        "Andy Gross" <agross@...nel.org>,
        "Bjorn Andersson" <bjorn.andersson@...aro.org>,
        "Konrad Dybcio" <konrad.dybcio@...ainline.org>,
        "Sumit Semwal" <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>
Cc:     "Robin Reckmann" <robin.reckmann@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH] i2c: qcom-geni: Fix GPI DMA buffer sync-back

Hi Robin,

On Sun Aug 7, 2022 at 4:04 PM CEST, Robin Reckmann wrote:
> Fix i2c transfers using GPI DMA mode for all message types that do not set
> the I2C_M_DMA_SAFE flag (e.g. SMBus "read byte").
>
> In this case a bounce buffer is returned by i2c_get_dma_safe_msg_buf(),
> and it has to synced back to the message after the transfer is done.
>
> Add missing assignment of dma buffer in geni_i2c_gpi().
>
> Set xferred in i2c_put_dma_safe_msg_buf() to true in case of no error to
> ensure the sync-back of this dma buffer to the message.
>
> Signed-off-by: Robin Reckmann <robin.reckmann@...il.com>

This makes I2C with GPI DMA work on sm6350/sm7725 fairphone-fp4!
Thanks for fixing this!

Tested-by: Luca Weiss <luca.weiss@...rphone.com>

Regards
Luca

> ---
>  drivers/i2c/busses/i2c-qcom-geni.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index 6ac402ea58fb..d3541e94794e 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -484,12 +484,12 @@ static void geni_i2c_gpi_unmap(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>  {
>  	if (tx_buf) {
>  		dma_unmap_single(gi2c->se.dev->parent, tx_addr, msg->len, DMA_TO_DEVICE);
> -		i2c_put_dma_safe_msg_buf(tx_buf, msg, false);
> +		i2c_put_dma_safe_msg_buf(tx_buf, msg, !gi2c->err);
>  	}
>  
>  	if (rx_buf) {
>  		dma_unmap_single(gi2c->se.dev->parent, rx_addr, msg->len, DMA_FROM_DEVICE);
> -		i2c_put_dma_safe_msg_buf(rx_buf, msg, false);
> +		i2c_put_dma_safe_msg_buf(rx_buf, msg, !gi2c->err);
>  	}
>  }
>  
> @@ -553,6 +553,7 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>  	desc->callback_param = gi2c;
>  
>  	dmaengine_submit(desc);
> +	*buf = dma_buf;
>  	*dma_addr_p = addr;
>  
>  	return 0;
> -- 
> 2.25.1