linux-kernel - Re: [PATCH 04/13] spi: spi-fsl-lpspi: Clear status register after disabling the module

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Message-ID: <aJ4VpLhI+hZU+cpj@lizhi-Precision-Tower-5810>
Date: Thu, 14 Aug 2025 12:58:12 -0400
From: Frank Li <Frank.li@....com>
To: James Clark <james.clark@...aro.org>
Cc: Mark Brown <broonie@...nel.org>, Clark Wang <xiaoning.wang@....com>,
	Fugang Duan <B38611@...escale.com>, Gao Pan <pandy.gao@....com>,
	Fugang Duan <fugang.duan@....com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Larisa Grigore <larisa.grigore@....nxp.com>,
	Larisa Grigore <larisa.grigore@....com>,
	Ghennadi Procopciuc <ghennadi.procopciuc@....com>,
	Ciprianmarian Costea <ciprianmarian.costea@....com>, s32@....com,
	linux-spi@...r.kernel.org, imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 04/13] spi: spi-fsl-lpspi: Clear status register after
 disabling the module

On Thu, Aug 14, 2025 at 05:06:44PM +0100, James Clark wrote:
> From: Larisa Grigore <larisa.grigore@....com>
>
> Clear the error flags after disabling the module to avoid the case when
> a flag is set between when the flags were just cleared, and when the
> module is disabled.

between flags clear and module disable

And use SR_CLEAR_MASK to replace hardcoded value for improved readability


Reviewed-by: Frank Li <Frank.Li@....com>

>
> Although fsl_lpspi_reset() was only introduced in commit a15dc3d657fa
> ("spi: lpspi: Fix CLK pin becomes low before one transfer"), the
> original driver only reset SR in the interrupt handler, making it
> vulnerable to the same issue. Therefore the fixes commit is set at the
> introduction of the driver.
>
> Fixes: 5314987de5e5 ("spi: imx: add lpspi bus driver")
> Signed-off-by: Larisa Grigore <larisa.grigore@....com>
> Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@....com>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>  drivers/spi/spi-fsl-lpspi.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
> index aab92ee7eb94..79b170426bee 100644
> --- a/drivers/spi/spi-fsl-lpspi.c
> +++ b/drivers/spi/spi-fsl-lpspi.c
> @@ -82,6 +82,8 @@
>  #define TCR_RXMSK	BIT(19)
>  #define TCR_TXMSK	BIT(18)
>
> +#define SR_CLEAR_MASK	GENMASK(13, 8)
> +
>  struct fsl_lpspi_devtype_data {
>  	u8 prescale_max;
>  };
> @@ -536,14 +538,13 @@ static int fsl_lpspi_reset(struct fsl_lpspi_data *fsl_lpspi)
>  		fsl_lpspi_intctrl(fsl_lpspi, 0);
>  	}
>
> -	/* W1C for all flags in SR */
> -	temp = 0x3F << 8;
> -	writel(temp, fsl_lpspi->base + IMX7ULP_SR);
> -
>  	/* Clear FIFO and disable module */
>  	temp = CR_RRF | CR_RTF;
>  	writel(temp, fsl_lpspi->base + IMX7ULP_CR);
>
> +	/* W1C for all flags in SR */
> +	writel(SR_CLEAR_MASK, fsl_lpspi->base + IMX7ULP_SR);
> +
>  	return 0;
>  }
>
>
> --
> 2.34.1
>