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spi: atmel-quadspi: Add support for configuring CS timing

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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@microchip.com>
Link: https://lore.kernel.org/r/20221117105249.115649-5-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Tudor Ambarus 2022-11-17 12:52:45 +02:00 committed by Mark Brown
parent 684a47847a
commit f732646d0c
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1 changed files with 34 additions and 0 deletions
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34
drivers/spi/atmel-quadspi.c
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@ -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;