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 10:10:14 +0000
From:   Chuanhua Han <chuanhua.han@....com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
CC:     "broonie@...nel.org" <broonie@...nel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "eha@...f.com" <eha@...f.com>
Subject: RE: [PATCH v2 2/4] spi: spi-fsl-dspi: Fix delete the processing of
 undefined bitmask for rxdata



> -----Original Message-----
> From: Boris Brezillon <boris.brezillon@...tlin.com>
> Sent: 2018年9月30日 18:07
> 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
In xspi mode, the value of rxdata after the statement is processed is equal to 0 no matter what data is received.
> 
> 	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)