The DesignWare SPI controller supports configurable bits_per_word (typically 4-32 bits), but this was previously hardcoded to 8 bits in the driver initialization.
This patch enables bits_per_word to be set dynamically by upper-level device drivers, matching the approach used in Linux. The controller reads the bits_per_word value from the spi_slave structure during each transfer, allowing different SPI devices on the same bus to use different word sizes. Implementation details: - Read slave->bits_per_word in dw_spi_xfer() before each transfer - Validate requested value against controller capabilities (4 to max_xfer) - Default to 8 bits if not set (maintains backward compatibility) This follows the Linux model where spi_device drivers set bits_per_word, and the controller driver reads it in the transfer function. Device drivers can now set slave->bits_per_word before calling spi_xfer(). Example usage in device driver: slave->bits_per_word = 16; spi_xfer(slave, ...); Backward compatible: Existing drivers that don't set bits_per_word will continue to work with the default 8-bit transfers. Signed-off-by: Boon Khai Ng <[email protected]> --- drivers/spi/designware_spi.c | 12 ++++++++++++ include/spi.h | 1 + 2 files changed, 13 insertions(+) diff --git a/drivers/spi/designware_spi.c b/drivers/spi/designware_spi.c index b520c727900..0df9a4f5abd 100644 --- a/drivers/spi/designware_spi.c +++ b/drivers/spi/designware_spi.c @@ -497,6 +497,7 @@ static int dw_spi_xfer(struct udevice *dev, unsigned int bitlen, { struct udevice *bus = dev->parent; struct dw_spi_priv *priv = dev_get_priv(bus); + struct spi_slave *slave = dev_get_parent_priv(dev); const u8 *tx = dout; u8 *rx = din; int ret = 0; @@ -504,6 +505,17 @@ static int dw_spi_xfer(struct udevice *dev, unsigned int bitlen, u32 val; u32 cs; + /* Get bits_per_word from slave (set by device driver) */ + if (slave->bits_per_word >= 4 && slave->bits_per_word <= priv->max_xfer) { + priv->bits_per_word = slave->bits_per_word; + } else if (slave->bits_per_word == 0) { + priv->bits_per_word = 8; /* Default if not set */ + } else { + dev_warn(dev, "Invalid bits_per_word %u, using 8\n", + slave->bits_per_word); + priv->bits_per_word = 8; + } + /* spi core configured to do 8 bit transfers */ if (bitlen % 8) { dev_err(dev, "Non byte aligned SPI transfer.\n"); diff --git a/include/spi.h b/include/spi.h index 95e7d5b1556..035d50f6b3a 100644 --- a/include/spi.h +++ b/include/spi.h @@ -159,6 +159,7 @@ struct spi_slave { unsigned int max_write_size; void *memory_map; + u8 bits_per_word; u8 flags; #define SPI_XFER_BEGIN BIT(0) /* Assert CS before transfer */ #define SPI_XFER_END BIT(1) /* Deassert CS after transfer */ -- 2.43.7
