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

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Message-ID: <40b29323-66db-492c-be00-71ff87f48d77@linaro.org>
Date: Mon, 18 Aug 2025 14:21:26 +0100
From: James Clark <james.clark@...aro.org>
To: Frank Li <Frank.li@....com>
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 14/08/2025 5:58 pm, Frank Li wrote:
> 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
> 

Ack

> 
> 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
>>