linux-kernel - Re: [PATCH v2 2/4] spi: spi-fsl-dspi: Fix delete the processing of undefined bitmask for rxdata

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Date:   Sun, 30 Sep 2018 12:06:59 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Chuanhua Han <chuanhua.han@....com>
Cc:     broonie@...nel.org, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org, eha@...f.com
Subject: Re: [PATCH v2 2/4] spi: spi-fsl-dspi: Fix delete the processing of
 undefined bitmask for rxdata

On Sun, 30 Sep 2018 17:25:33 +0800
Chuanhua Han <chuanhua.han@....com> wrote:

> This patch fixes the problem of rxdata being equal to 0 during the XSPI
> mode transfer of the dspi controller.
> In XSPI mode, If it is not deleted, the value of rxdata will be equal
> to 0, and the data received will not be received correctly, causing the
> receiving transfer of the spi to fail.
> 
> Signed-off-by: Chuanhua Han <chuanhua.han@....com>
> ---
> Changes in v2:
>  -The original patch is divided into multiple patches(the original
> patch theme is "spi: spi-fsl-dspi: Fix support for XSPI transport
> mode"),one of which is segmented.
> 
>  drivers/spi/spi-fsl-dspi.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
> index 3082e72e4f6c..4dc1064bf408 100644
> --- a/drivers/spi/spi-fsl-dspi.c
> +++ b/drivers/spi/spi-fsl-dspi.c
> @@ -243,9 +243,6 @@ static void dspi_push_rx(struct fsl_dspi *dspi, u32 rxdata)
>  	if (!dspi->rx)
>  		return;
>  
> -	/* Mask of undefined bits */
> -	rxdata &= (1 << dspi->bits_per_word) - 1;
> -

Why not

	if (dspi->bits_per_word)
		rxdata &= (1 << dspi->bits_per_word) - 1;

>  	if (dspi->bytes_per_word == 1)
>  		*(u8 *)dspi->rx = rxdata;
>  	else if (dspi->bytes_per_word == 2)