linux-kernel - Re: [PATCH v2 7/9] spi: spi-fsl-lpspi: Treat prescale

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Message-ID: <aLCcYMBqCF5XaaaN@lizhi-Precision-Tower-5810>
Date: Thu, 28 Aug 2025 14:13:52 -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>,
	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 v2 7/9] spi: spi-fsl-lpspi: Treat prescale_max == 0 as no
 erratum

On Thu, Aug 28, 2025 at 11:14:46AM +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 default prescale value
> for every new device's devdata, treat 0 as no limit (7) and only set a
> value when the erratum is present.
>
> Change the field to be 3 bits to catch out of range definitions.
>
> No functionality change.
>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---

Reviewed-by: Frank Li <Frank.Li@....com>
>  drivers/spi/spi-fsl-lpspi.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
> index f16449cf42bb..ea25e8dab0a4 100644
> --- a/drivers/spi/spi-fsl-lpspi.c
> +++ b/drivers/spi/spi-fsl-lpspi.c
> @@ -86,7 +86,7 @@
>  #define SR_CLEAR_MASK	GENMASK(13, 8)
>
>  struct fsl_lpspi_devtype_data {
> -	u8 prescale_max;
> +	u8 prescale_max : 3; /* 0 == no limit */
>  };
>
>  struct lpspi_config {
> @@ -132,15 +132,15 @@ 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 there is
> + * no prescale limit: https://www.nxp.com/docs/en/errata/i.MX93_1P87f.pdf
>   */
>  static const struct fsl_lpspi_devtype_data imx93_lpspi_devtype_data = {
>  	.prescale_max = 1,
>  };
>
>  static const struct fsl_lpspi_devtype_data imx7ulp_lpspi_devtype_data = {
> -	.prescale_max = 7,
> +	/* All defaults */
>  };
>
>  static const struct of_device_id fsl_lpspi_dt_ids[] = {
> @@ -324,7 +324,7 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi)
>  	int scldiv;
>
>  	perclk_rate = clk_get_rate(fsl_lpspi->clk_per);
> -	prescale_max = fsl_lpspi->devtype_data->prescale_max;
> +	prescale_max = fsl_lpspi->devtype_data->prescale_max ?: 7;
>
>  	if (!config.speed_hz) {
>  		dev_err(fsl_lpspi->dev,
>
> --
> 2.34.1
>