linux-kernel - Re: [V2] i2c: i2c-qcom-geni: Correct I2C TRE sequence

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Message-ID: <CAA8EJpr_KXsjTUYha7OVg4HLLJLqMRvJun9DnMkBFvq3R2nk=Q@mail.gmail.com>
Date: Tue, 30 Jan 2024 01:49:57 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Viken Dadhaniya <quic_vdadhani@...cinc.com>
Cc: andersson@...nel.org, konrad.dybcio@...aro.org, andi.shyti@...nel.org, 
	linux-arm-msm@...r.kernel.org, linux-i2c@...r.kernel.org, 
	linux-kernel@...r.kernel.org, vkoul@...nel.org, quic_bjorande@...cinc.com, 
	manivannan.sadhasivam@...aro.org, quic_msavaliy@...cinc.com, 
	quic_vtanuku@...cinc.com
Subject: Re: [V2] i2c: i2c-qcom-geni: Correct I2C TRE sequence

On Mon, 29 Jan 2024 at 08:10, Viken Dadhaniya <quic_vdadhani@...cinc.com> wrote:
>
> For i2c read operation, we are getting gsi mode timeout due
> to malformed TRE(Transfer Ring Element). Currently we are
> configuring incorrect TRE sequence in gpi driver
> (drivers/dma/qcom/gpi.c) as below
>
> - Sets up CONFIG
> - Sets up DMA tre
> - Sets up GO tre
>
> As per HPG(Hardware programming guide), We should configure TREs in below
> sequence for any i2c transfer
>
> - Sets up CONFIG tre
> - Sets up GO tre
> - Sets up DMA tre

It is not clear how this is relevant and/or affected by swapping
I2C_WRITE and I2C_READ gpi calls.

>
> For only write operation or write followed by read operation,
> existing software sequence is correct.
>
> for only read operation, TRE sequence need to be corrected.
> Hence, we have changed the sequence to submit GO tre before DMA tre.
>
> Tested covering i2c read/write transfer on QCM6490 RB3 board.

Please read Documentation/process/submitting-patches.rst, understand
it and write a proper commit message.

>
> Signed-off-by: Viken Dadhaniya <quic_vdadhani@...cinc.com>
> Fixes: commit d8703554f4de ("i2c: qcom-geni: Add support for GPI DMA")

As it was pointed out, this line shows ignorance of the mentioned file
and of the existing community practices.

> ---
> v1 -> v2:
> - Remove redundant check.
> - update commit log.
> - add fix tag.
> ---
> ---
>  drivers/i2c/busses/i2c-qcom-geni.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index 0d2e7171e3a6..da94df466e83 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -613,20 +613,20 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>
>                 peripheral.addr = msgs[i].addr;
>
> +               ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
> +                                   &tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
> +               if (ret)
> +                       goto err;
> +
>                 if (msgs[i].flags & I2C_M_RD) {
>                         ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
>                                             &rx_addr, &rx_buf, I2C_READ, gi2c->rx_c);
>                         if (ret)
>                                 goto err;
> -               }
> -
> -               ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
> -                                   &tx_addr, &tx_buf, I2C_WRITE, gi2c->tx_c);
> -               if (ret)
> -                       goto err;
>
> -               if (msgs[i].flags & I2C_M_RD)
>                         dma_async_issue_pending(gi2c->rx_c);
> +               }
> +
>                 dma_async_issue_pending(gi2c->tx_c);
>
>                 timeout = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>
>


-- 
With best wishes
Dmitry