[PATCH v4 03/16] spi: parse spi-max-post-config-frequency into post_config_max_speed_hz

[Santhosh Kumar K <s-k6@ti.com>]

Add post_config_max_speed_hz to struct spi_device and parse it from
the spi-max-post-config-frequency DT property in of_spi_parse_dt().

This supports SPI devices that operate at two distinct clock rates: a
conservative rate always reachable without controller configuration,
and a higher rate achievable only after controller-side configuration
such as PHY tuning. With both properties set, spi-max-frequency gives
the conservative pre-configuration rate and post_config_max_speed_hz
carries the post-configuration target for the SPI-MEM layer.

Zero when not set, preserving existing behaviour.

Signed-off-by: Santhosh Kumar K <s-k6@ti.com>
---
 drivers/spi/spi.c       | 2 ++
 include/linux/spi/spi.h | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 76e3563c523f..36951ab47a2f 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2599,6 +2599,8 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
 	/* Device speed */
 	if (!of_property_read_u32(nc, "spi-max-frequency", &value))
 		spi->max_speed_hz = value;
+	if (!of_property_read_u32(nc, "spi-max-post-config-frequency", &value))
+		spi->post_config_max_speed_hz = value;
 
 	/* Device CS delays */
 	of_spi_parse_dt_cs_delay(nc, &spi->cs_setup, "spi-cs-setup-delay-ns");
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index f6ed93eff00b..2d90ec91450a 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -139,6 +139,8 @@ extern void spi_transfer_cs_change_delay_exec(struct spi_message *msg,
  * @max_speed_hz: Maximum clock rate to be used with this chip
  *	(on this board); may be changed by the device's driver.
  *	The spi_transfer.speed_hz can override this for each transfer.
+ * @post_config_max_speed_hz: Maximum clock rate achievable after controller
+ *	configuration (e.g. PHY tuning); zero when not assigned.
  * @bits_per_word: Data transfers involve one or more words; word sizes
  *	like eight or 12 bits are common.  In-memory wordsizes are
  *	powers of two bytes (e.g. 20 bit samples use 32 bits).
@@ -191,6 +193,7 @@ struct spi_device {
 	struct device		dev;
 	struct spi_controller	*controller;
 	u32			max_speed_hz;
+	u32			post_config_max_speed_hz;
 	u8			bits_per_word;
 	bool			rt;
 #define SPI_NO_TX		BIT(31)		/* No transmit wire */
-- 
2.34.1