spi: Introduce spi-cs-setup-ns property

SPI NOR flashes have specific cs-setup time requirements without which
they can't work at frequencies close to their maximum supported frequency,
as they miss the first bits of the instruction command. Unrecognized
commands are ignored, thus the flash will be unresponsive. Introduce the
spi-cs-setup-ns property to allow spi devices to specify their cs setup
time.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20221117105249.115649-3-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 4ddd250481f5a9bb8cf5b5ddef0b334bce8d9910..b93a6085d9a0feaab65cb1faf1f7a1cc8872f93c 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2224,6 +2224,7 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
                           struct device_node *nc)
 {
        u32 value;
+       u16 cs_setup;
        int rc;
 
        /* Mode (clock phase/polarity/etc.) */
@@ -2309,6 +2310,11 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
        if (!of_property_read_u32(nc, "spi-max-frequency", &value))
                spi->max_speed_hz = value;
 
+       if (!of_property_read_u16(nc, "spi-cs-setup-ns", &cs_setup)) {
+               spi->cs_setup.value = cs_setup;
+               spi->cs_setup.unit = SPI_DELAY_UNIT_NSECS;
+       }
+
        return 0;
 }