linux-kernel - Re: [PATCH 08/13] spi: spi-fsl-lpspi: Make prescale erratum a bool

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Message-ID: <7c4cb21a-e1ea-4931-9b51-91cfc8217155@linaro.org>
Date: Mon, 18 Aug 2025 14:54:36 +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>,
 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 08/13] spi: spi-fsl-lpspi: Make prescale erratum a bool



On 14/08/2025 7:36 pm, Frank Li wrote:
> On Thu, Aug 14, 2025 at 05:06:48PM +0100, James Clark wrote:
>> This erratum only ever results in a max value of 1, otherwise the full 3
>> bits are available. To avoid repeating the same prescale values for
>> every new device's devdata, make it a bool.
>>
>> Signed-off-by: James Clark <james.clark@...aro.org>
>> ---
>>   drivers/spi/spi-fsl-lpspi.c | 12 +++++++-----
>>   1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
>> index 332a852b746f..1013d5c994e9 100644
>> --- a/drivers/spi/spi-fsl-lpspi.c
>> +++ b/drivers/spi/spi-fsl-lpspi.c
>> @@ -96,7 +96,7 @@ static const char * const pincfgs[] = {
>>   };
>>
>>   struct fsl_lpspi_devtype_data {
>> -	u8 prescale_max;
>> +	bool prescale_err : 1;
>>   };
>>
>>   struct lpspi_config {
>> @@ -144,13 +144,16 @@ struct fsl_lpspi_data {
>>   /*
>>    * ERR051608 fixed or not:
>>    * https://www.nxp.com/docs/en/errata/i.MX93_1P87f.pdf
>> + *
>> + * Devices with ERR051608 have a max TCR_PRESCALE value of 1, otherwise the full
>> + * 3 bits are available (0-7).
>>    */
>>   static const struct fsl_lpspi_devtype_data imx93_lpspi_devtype_data = {
>> -	.prescale_max = 1,
>> +	.prescale_err = true,
> 
> I think prescale_max is good and clear enough, you can treat 0 as no
> limit for prescale.
> 
> Frank

Ack

>>   };
>>
>>   static const struct fsl_lpspi_devtype_data imx7ulp_lpspi_devtype_data = {
>> -	.prescale_max = 7,
>> +	.prescale_err = false,
>>   };
>>
>>   static const struct of_device_id fsl_lpspi_dt_ids[] = {
>> @@ -329,12 +332,11 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi)
>>   {
>>   	struct lpspi_config config = fsl_lpspi->config;
>>   	unsigned int perclk_rate, div;
>> -	u8 prescale_max;
>> +	u8 prescale_max = fsl_lpspi->devtype_data->prescale_err ? 1 : 7;
>>   	u8 prescale;
>>   	int scldiv;
>>
>>   	perclk_rate = clk_get_rate(fsl_lpspi->clk_per);
>> -	prescale_max = fsl_lpspi->devtype_data->prescale_max;
>>
>>   	if (!config.speed_hz) {
>>   		dev_err(fsl_lpspi->dev,
>>
>> --
>> 2.34.1
>>