[PATCH v3 7/9] spi: stm32: add support for bits-per-word setting

[Patrice CHOTARD]

On 2/25/26 17:16, Dario Binacchi wrote:
> Implement the set_wordlen operation to allow dynamic bus width
> configuration. This is required for peripherals with non-standard
> requirements, such as display panels that need 9-bit word transfers
> during the initialization and setup phase.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi at amarulasolutions.com>
> 
> ---
> 
> Changes in v3:
> - Move the stm32_spi_is_enabled() implementation in the previous patch
> 
>  drivers/spi/stm32_spi.c | 57 +++++++++++++++++++++++++++++++++++++----
>  1 file changed, 52 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/spi/stm32_spi.c b/drivers/spi/stm32_spi.c
> index 70eb8735e03d..9d095b280a70 100644
> --- a/drivers/spi/stm32_spi.c
> +++ b/drivers/spi/stm32_spi.c
> @@ -384,6 +384,44 @@ static int stm32_spi_set_speed(struct udevice *bus, uint hz)
>  	return 0;
>  }
>  
> +static int _stm32_spi_set_wordlen(struct udevice *bus, unsigned int wordlen)
> +{
> +	struct stm32_spi_priv *priv = dev_get_priv(bus);
> +	struct stm32_spi_plat *plat = dev_get_plat(bus);
> +	void __iomem *base = plat->base;
> +	bool spi_enabled;
> +
> +	if ((wordlen - 1) < SPI_CFG1_DSIZE_MIN ||
> +	    (wordlen - 1) > SPI_CFG1_DSIZE) {
> +		dev_err(bus, "Cannot set wordlen to %u [%d - %d]\n",
> +			wordlen, SPI_CFG1_DSIZE_MIN + 1,
> +			SPI_CFG1_DSIZE + 1);
> +		return -EINVAL;
> +	}
> +
> +	spi_enabled = stm32_spi_is_enabled(plat->base);
> +	if (spi_enabled)
> +		stm32_spi_disable(plat->base);
> +
> +	dev_dbg(bus, "bits_per_word=%d\n", wordlen);
> +
> +	priv->cur_bpw = wordlen;
> +	clrsetbits_le32(base + STM32_SPI_CFG1, SPI_CFG1_DSIZE,
> +			priv->cur_bpw - 1);
> +
> +	if (spi_enabled)
> +		stm32_spi_enable(plat->base);
> +
> +	return 0;
> +}
> +
> +static int stm32_spi_set_wordlen(struct udevice *slave, unsigned int wordlen)
> +{
> +	struct udevice *bus = dev_get_parent(slave);
> +
> +	return _stm32_spi_set_wordlen(bus, wordlen);
> +}
> +
>  static int stm32_spi_xfer(struct udevice *slave, unsigned int bitlen,
>  			  const void *dout, void *din, unsigned long flags)
>  {
> @@ -397,11 +435,19 @@ static int stm32_spi_xfer(struct udevice *slave, unsigned int bitlen,
>  	u32 xferlen;
>  	u32 mode;
>  	int xfer_status = 0;
> +	int nb_words;
>  
>  	xferlen = bitlen / 8;
>  
> -	if (xferlen <= SPI_CR2_TSIZE)
> -		writel(xferlen, base + STM32_SPI_CR2);
> +	if (priv->cur_bpw <= 8)
> +		nb_words = xferlen;
> +	else if (priv->cur_bpw <= 16)
> +		nb_words = DIV_ROUND_UP(xferlen * 8, 16);
> +	else
> +		nb_words = DIV_ROUND_UP(xferlen * 8, 32);
> +
> +	if (nb_words <= SPI_CR2_TSIZE)
> +		writel(nb_words, base + STM32_SPI_CR2);
>  	else
>  		return -EMSGSIZE;
>  
> @@ -409,6 +455,8 @@ static int stm32_spi_xfer(struct udevice *slave, unsigned int bitlen,
>  	priv->rx_buf = din;
>  	priv->tx_len = priv->tx_buf ? xferlen : 0;
>  	priv->rx_len = priv->rx_buf ? xferlen : 0;
> +	dev_dbg(bus, "bitlen: %d, xferlen: %d, nb_words: %d\n",
> +		bitlen, xferlen, nb_words);
>  
>  	mode = SPI_FULL_DUPLEX;
>  	if (!priv->tx_buf)
> @@ -570,9 +618,7 @@ static int stm32_spi_probe(struct udevice *dev)
>  	priv->fifo_size = stm32_spi_get_fifo_size(dev);
>  	priv->cur_mode = SPI_FULL_DUPLEX;
>  	priv->cur_xferlen = 0;
> -	priv->cur_bpw = SPI_DEFAULT_WORDLEN;
> -	clrsetbits_le32(base + STM32_SPI_CFG1, SPI_CFG1_DSIZE,
> -			priv->cur_bpw - 1);
> +	_stm32_spi_set_wordlen(dev, SPI_DEFAULT_WORDLEN);
>  
>  	for (i = 0; i < ARRAY_SIZE(plat->cs_gpios); i++) {
>  		if (!dm_gpio_is_valid(&plat->cs_gpios[i]))
> @@ -633,6 +679,7 @@ static const struct dm_spi_ops stm32_spi_ops = {
>  	.release_bus	= stm32_spi_release_bus,
>  	.set_mode	= stm32_spi_set_mode,
>  	.set_speed	= stm32_spi_set_speed,
> +	.set_wordlen    = stm32_spi_set_wordlen,
>  	.xfer		= stm32_spi_xfer,
>  };
>  
Reviewed-by: Patrice Chotard <patrice.chotard at foss.st.com>

Thanks
Patrice