Currently, the RSPI driver always tries to use the maximum configured
bit rate for communicating with a slave device, even if the transfer(s)
in the current message specify a lower rate.
Use the mininum rate specified in the message instead.
Rename rspi_data.max_speed_hz accordingly.
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
drivers/spi/spi-rspi.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
index 0e786af546c9f513..1b635d6b7881f5b9 100644
--- a/drivers/spi/spi-rspi.c
+++ b/drivers/spi/spi-rspi.c
@@ -179,7 +179,7 @@
struct rspi_data {
void __iomem *addr;
- u32 max_speed_hz;
+ u32 speed_hz;
struct spi_controller *ctlr;
struct platform_device *pdev;
wait_queue_head_t wait;
@@ -258,8 +258,7 @@ static int rspi_set_config_register(struct rspi_data *rspi, int access_size)
rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
/* Sets transfer bit rate */
- spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk),
- 2 * rspi->max_speed_hz) - 1;
+ spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz) - 1;
rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
/* Disable dummy transmission, set 16-bit word access, 1 frame */
@@ -299,14 +298,14 @@ static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size)
clksrc = clk_get_rate(rspi->clk);
while (div < 3) {
- if (rspi->max_speed_hz >= clksrc/4) /* 4=(CLK/2)/2 */
+ if (rspi->speed_hz >= clksrc/4) /* 4=(CLK/2)/2 */
break;
div++;
clksrc /= 2;
}
/* Sets transfer bit rate */
- spbr = DIV_ROUND_UP(clksrc, 2 * rspi->max_speed_hz) - 1;
+ spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1;
rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
rspi->spcmd |= div << 2;
@@ -341,7 +340,7 @@ static int qspi_set_config_register(struct rspi_data *rspi, int access_size)
rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
/* Sets transfer bit rate */
- spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->max_speed_hz);
+ spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz);
rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
/* Disable dummy transmission, set byte access */
@@ -949,9 +948,24 @@ static int rspi_prepare_message(struct spi_controller *ctlr,
{
struct rspi_data *rspi = spi_controller_get_devdata(ctlr);
struct spi_device *spi = msg->spi;
+ const struct spi_transfer *xfer;
int ret;
- rspi->max_speed_hz = spi->max_speed_hz;
+ /*
+ * As the Bit Rate Register must not be changed while the device is
+ * active, all transfers in a message must use the same bit rate.
+ * In theory, the sequencer could be enabled, and each Command Register
+ * could divide the base bit rate by a different value.
+ * However, most RSPI variants do not have Transfer Data Length
+ * Multiplier Setting Registers, so each sequence step would be limited
+ * to a single word, making this feature unsuitable for large
+ * transfers, which would gain most from it.
+ */
+ rspi->speed_hz = spi->max_speed_hz;
+ list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+ if (xfer->speed_hz < rspi->speed_hz)
+ rspi->speed_hz = xfer->speed_hz;
+ }
rspi->spcmd = SPCMD_SSLKP;
if (spi->mode & SPI_CPOL)
--
2.17.1
