linux-kernel - Re: [PATCH 1/6] spi: spi-fsl-dspi: Don't access reserved fields in SPI

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Message-ID: <c35b3c34123b43b26204a2cf360e7ec1@walle.cc>
Date:   Mon, 09 Mar 2020 19:05:09 +0100
From:   Michael Walle <michael@...le.cc>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     broonie@...nel.org, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org, shawnguo@...nel.org,
        robh+dt@...nel.org, mark.rutland@....com,
        devicetree@...r.kernel.org, eha@...f.com, angelo@...am.it,
        andrew.smirnov@...il.com, gustavo@...eddedor.com, weic@...dia.com,
        mhosny@...dia.com, peng.ma@....com
Subject: Re: [PATCH 1/6] spi: spi-fsl-dspi: Don't access reserved fields in
 SPI_MCR

Am 2020-03-09 15:56, schrieb Vladimir Oltean:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> The SPI_MCR_PCSIS macro assumes that the controller has a number of 
> chip
> select signals equal to 6. That is not always the case, but actually is
> described through the driver-specific " signals equal to 6. That is not
> always the case, but actually is described through the driver-specific
> "spi-num-chipselects" device tree binding.

Repeated sentence? Was this your intention?

-michael

> LS1028A for example only has
> 4 chip selects.
> 
> Don't write to the upper bits of the PCSIS field, which are reserved in
> the reference manual.
> 
> Fixes: 349ad66c0ab0 ("spi:Add Freescale DSPI driver for Vybrid VF610 
> platform")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  drivers/spi/spi-fsl-dspi.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
> index 0683a3fbd48c..0ce26c1cbf62 100644
> --- a/drivers/spi/spi-fsl-dspi.c
> +++ b/drivers/spi/spi-fsl-dspi.c
> @@ -22,7 +22,7 @@
> 
>  #define SPI_MCR				0x00
>  #define SPI_MCR_MASTER			BIT(31)
> -#define SPI_MCR_PCSIS			(0x3F << 16)
> +#define SPI_MCR_PCSIS(x)		((x) << 16)
>  #define SPI_MCR_CLR_TXF			BIT(11)
>  #define SPI_MCR_CLR_RXF			BIT(10)
>  #define SPI_MCR_XSPI			BIT(3)
> @@ -1197,7 +1197,10 @@ static const struct regmap_config
> dspi_xspi_regmap_config[] = {
> 
>  static void dspi_init(struct fsl_dspi *dspi)
>  {
> -	unsigned int mcr = SPI_MCR_PCSIS;
> +	unsigned int mcr;
> +
> +	/* Set idle states for all chip select signals to high */
> +	mcr = SPI_MCR_PCSIS(GENMASK(dspi->ctlr->num_chipselect - 1, 0));
> 
>  	if (dspi->devtype_data->trans_mode == DSPI_XSPI_MODE)
>  		mcr |= SPI_MCR_XSPI;