[PATCH v2 3/3] spi: spi-cadence: supports transmission with bits_per_word of 16 and 32

Jun Guo
2025-10-27T08:43:13Z

The default FIFO data width of the Cadence SPI IP is 8 bits, but
the hardware supports configurations of 16 bits and 32 bits.
This patch enhances the driver to support communication with both
16-bits and 32-bits FIFO data widths.

Signed-off-by: Jun Guo <jun.guo@cixtech.com>
---
drivers/spi/spi-cadence.c | 106 +++++++++++++++++++++++++++++++++-----
1 file changed, 93 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index 5ae09b21d23a..47054da630d0 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -109,6 +109,7 @@
* @rxbuf: Pointer to the RX buffer
* @tx_bytes: Number of bytes left to transfer
* @rx_bytes: Number of bytes requested
+ * @n_bytes: Number of bytes per word
* @dev_busy: Device busy flag
* @is_decoded_cs: Flag for decoder property set or not
* @tx_fifo_depth: Depth of the TX FIFO
@@ -120,16 +121,24 @@ struct cdns_spi {
struct clk *pclk;
unsigned int clk_rate;
u32 speed_hz;
- const u8 *txbuf;
- u8 *rxbuf;
+ const void *txbuf;
+ void *rxbuf;
int tx_bytes;
int rx_bytes;
+ u8 n_bytes;
u8 dev_busy;
u32 is_decoded_cs;
unsigned int tx_fifo_depth;
struct reset_control *rstc;
};

+enum cdns_spi_frame_n_bytes {
+ CDNS_SPI_N_BYTES_NULL = 0,
+ CDNS_SPI_N_BYTES_U8 = 1,
+ CDNS_SPI_N_BYTES_U16 = 2,
+ CDNS_SPI_N_BYTES_U32 = 4
+};
+
/* Macros for the SPI controller read/write */
static inline u32 cdns_spi_read(struct cdns_spi *xspi, u32 offset)
{
@@ -305,6 +314,78 @@ static int cdns_spi_setup_transfer(struct spi_device *spi,
return 0;
}

+static u8 cdns_spi_n_bytes(struct spi_transfer *transfer)
+{
+ if (transfer->bits_per_word <= 8)
+ return CDNS_SPI_N_BYTES_U8;
+ else if (transfer->bits_per_word <= 16)
+ return CDNS_SPI_N_BYTES_U16;
+ else
+ return CDNS_SPI_N_BYTES_U32;
+}
+
+static inline void cdns_spi_reader(struct cdns_spi *xspi)
+{
+ u32 rxw = 0;
+
+ if (xspi->rxbuf && !IS_ALIGNED((uintptr_t)xspi->rxbuf, xspi->n_bytes)) {
+ pr_err("%s: rxbuf address is not aligned for %d bytes\n",
+ __func__, xspi->n_bytes);
+ return;
+ }
+
+ rxw = cdns_spi_read(xspi, CDNS_SPI_RXD);
+ if (xspi->rxbuf) {
+ switch (xspi->n_bytes) {
+ case CDNS_SPI_N_BYTES_U8:
+ *(u8 *)xspi->rxbuf = rxw;
+ break;
+ case CDNS_SPI_N_BYTES_U16:
+ *(u16 *)xspi->rxbuf = rxw;
+ break;
+ case CDNS_SPI_N_BYTES_U32:
+ *(u32 *)xspi->rxbuf = rxw;
+ break;
+ default:
+ pr_err("%s invalid n_bytes %d\n", __func__,
+ xspi->n_bytes);
+ return;
+ }
+ xspi->rxbuf = (u8 *)xspi->rxbuf + xspi->n_bytes;
+ }
+}
+
+static inline void cdns_spi_writer(struct cdns_spi *xspi)
+{
+ u32 txw = 0;
+
+ if (xspi->txbuf && !IS_ALIGNED((uintptr_t)xspi->txbuf, xspi->n_bytes)) {
+ pr_err("%s: txbuf address is not aligned for %d bytes\n",
+ __func__, xspi->n_bytes);
+ return;
+ }
+
+ if (xspi->txbuf) {
+ switch (xspi->n_bytes) {
+ case CDNS_SPI_N_BYTES_U8:
+ txw = *(u8 *)xspi->txbuf;
+ break;
+ case CDNS_SPI_N_BYTES_U16:
+ txw = *(u16 *)xspi->txbuf;
+ break;
+ case CDNS_SPI_N_BYTES_U32:
+ txw = *(u32 *)xspi->txbuf;
+ break;
+ default:
+ pr_err("%s invalid n_bytes %d\n", __func__,
+ xspi->n_bytes);
+ return;
+ }
+ cdns_spi_write(xspi, CDNS_SPI_TXD, txw);
+ xspi->txbuf = (u8 *)xspi->txbuf + xspi->n_bytes;
+ }
+}
+
/**
* cdns_spi_process_fifo - Fills the TX FIFO, and drain the RX FIFO
* @xspi: Pointer to the cdns_spi structure
@@ -321,23 +402,14 @@ static void cdns_spi_process_fifo(struct cdns_spi *xspi, int ntx, int nrx)

while (ntx || nrx) {
if (nrx) {
- u8 data = cdns_spi_read(xspi, CDNS_SPI_RXD);
-
- if (xspi->rxbuf)
- *xspi->rxbuf++ = data;
-
+ cdns_spi_reader(xspi);
nrx--;
}

if (ntx) {
- if (xspi->txbuf)
- cdns_spi_write(xspi, CDNS_SPI_TXD, *xspi->txbuf++);
- else
- cdns_spi_write(xspi, CDNS_SPI_TXD, 0);
-
+ cdns_spi_writer(xspi);
ntx--;
}
-
}
}

@@ -454,6 +526,10 @@ static int cdns_transfer_one(struct spi_controller *ctlr,
if (cdns_spi_read(xspi, CDNS_SPI_ISR) & CDNS_SPI_IXR_TXFULL)
udelay(10);

+ xspi->n_bytes = cdns_spi_n_bytes(transfer);
+ xspi->tx_bytes = DIV_ROUND_UP(xspi->tx_bytes, xspi->n_bytes);
+ xspi->rx_bytes = DIV_ROUND_UP(xspi->rx_bytes, xspi->n_bytes);
+
cdns_spi_process_fifo(xspi, xspi->tx_fifo_depth, 0);

cdns_spi_write(xspi, CDNS_SPI_IER, CDNS_SPI_IXR_DEFAULT);
@@ -654,6 +730,9 @@ static int cdns_spi_probe(struct platform_device *pdev)
ctlr->mode_bits = SPI_CPOL | SPI_CPHA;
ctlr->bits_per_word_mask = SPI_BPW_MASK(8);

+ if (of_device_is_compatible(pdev->dev.of_node, "cix,sky1-spi-r1p6"))
+ ctlr->bits_per_word_mask |= SPI_BPW_MASK(16) | SPI_BPW_MASK(32);
+
if (!spi_controller_is_target(ctlr)) {
ctlr->mode_bits |= SPI_CS_HIGH;
ctlr->set_cs = cdns_spi_chipselect;
@@ -797,6 +876,7 @@ static const struct dev_pm_ops cdns_spi_dev_pm_ops = {

static const struct of_device_id cdns_spi_of_match[] = {
{ .compatible = "xlnx,zynq-spi-r1p6" },
+ { .compatible = "cix,sky1-spi-r1p6" },
{ .compatible = "cdns,spi-r1p6" },
{ /* end of table */ }
};
--
2.34.1