linux-kernel - Re: [PATCH] i2c: qcom-geni: make sure I2C hub controllers can't use SE DMA

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Message-ID: <49f067c0-20d3-4039-95e6-fc19ce48881d@oss.qualcomm.com>
Date: Thu, 30 Oct 2025 10:26:42 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Mukesh Kumar Savaliya <mukesh.savaliya@....qualcomm.com>,
        Viken Dadhaniya <viken.dadhaniya@....qualcomm.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Wolfram Sang <wsa@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>
Cc: 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: make sure I2C hub controllers can't use
 SE DMA

On 10/29/25 7:07 PM, Neil Armstrong wrote:
> The I2C Hub controller is a simpler GENI I2C variant that doesn't
> support DMA at all, add a no_dma flag to make sure it nevers selects
> the SE DMA mode with mappable 32bytes long transfers.
> 
> Fixes: cacd9643eca7 ("i2c: qcom-geni: add support for I2C Master Hub variant")
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>  drivers/i2c/busses/i2c-qcom-geni.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index 43fdd89b8beb..bfb352b04902 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -97,6 +97,7 @@ struct geni_i2c_dev {
>  	dma_addr_t dma_addr;
>  	struct dma_chan *tx_c;
>  	struct dma_chan *rx_c;
> +	bool no_dma;
>  	bool gpi_mode;
>  	bool abort_done;
>  };
> @@ -425,7 +426,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
>  	size_t len = msg->len;
>  	struct i2c_msg *cur;
>  
> -	dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> +	dma_buf = gi2c->no_dma ? NULL : i2c_get_dma_safe_msg_buf(msg, 32);

Not a huge fan of putting the ternary operator here, but I don't
mind that much either

Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>

Konrad