The at91 QSPI IP uses a default value of half of the period of the QSPI
clock period for the cs-setup time, which is not always enough, an example
being the sst26vf064b SPI NOR flash which requires a minimum cs-setup time
of 5 ns. It was observed that none of the at91 SoCs can fulfill the
minimum CS setup time for the aforementioned flash, as they operate at
high frequencies and half a period does not suffice for the required CS
setup time. Add support for configuring the CS timing in the controller.
Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
---
drivers/spi/atmel-quadspi.c | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)
diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
index 976a217e356d..70637e46290a 100644
--- a/drivers/spi/atmel-quadspi.c
+++ b/drivers/spi/atmel-quadspi.c
@@ -510,6 +510,39 @@ static int atmel_qspi_setup(struct spi_device *spi)
return 0;
}
+static int atmel_qspi_set_cs_timing(struct spi_device *spi)
+{
+ struct spi_controller *ctrl = spi->master;
+ struct atmel_qspi *aq = spi_controller_get_devdata(ctrl);
+ unsigned long clk_rate;
+ u32 cs_setup;
+ int delay;
+ int ret;
+
+ delay = spi_delay_to_ns(&spi->cs_setup, NULL);
+ if (delay <= 0)
+ return delay;
+
+ clk_rate = clk_get_rate(aq->pclk);
+ if (!clk_rate)
+ return -EINVAL;
+
+ cs_setup = DIV_ROUND_UP((delay * DIV_ROUND_UP(clk_rate, 1000000)),
+ 1000);
+
+ ret = pm_runtime_resume_and_get(ctrl->dev.parent);
+ if (ret < 0)
+ return ret;
+
+ aq->scr |= QSPI_SCR_DLYBS(cs_setup);
+ atmel_qspi_write(aq->scr, aq, QSPI_SCR);
+
+ pm_runtime_mark_last_busy(ctrl->dev.parent);
+ pm_runtime_put_autosuspend(ctrl->dev.parent);
+
+ return 0;
+}
+
static void atmel_qspi_init(struct atmel_qspi *aq)
{
/* Reset the QSPI controller */
@@ -555,6 +588,7 @@ static int atmel_qspi_probe(struct platform_device *pdev)
ctrl->mode_bits = SPI_RX_DUAL | SPI_RX_QUAD | SPI_TX_DUAL | SPI_TX_QUAD;
ctrl->setup = atmel_qspi_setup;
+ ctrl->set_cs_timing = atmel_qspi_set_cs_timing;
ctrl->bus_num = -1;
ctrl->mem_ops = &atmel_qspi_mem_ops;
ctrl->num_chipselect = 1;
--
2.25.1
