env_spi: support overriding spi dev from board code

This enables boards to choose where to/from the environment
should be saved/loaded. They can then for example support using
the same device (dynamically) from which the bootloader was
launched to load and save env data and do not have to
define CONFIG_ENV_SPI_BUS statically.

In my use case, the environment needs to be on the same device I
booted from. It can be the QSPI or OSPI device.
I therefore would override spi_get_env_dev in the board code,
read the bootmode registers to determine where we booted from
and return the corresponding device index.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20240614124811.22945-2-venkatesh.abbarapu@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com> # Move spi_get_env_dev to sf.c

env/sf.c

@@ -38,14 +38,24 @@ static ulong env_new_offset	= CONFIG_ENV_OFFSET_REDUND;
 
 DECLARE_GLOBAL_DATA_PTR;
 
+__weak int spi_get_env_dev(void)
+{
+#ifdef CONFIG_ENV_SPI_BUS
+	return CONFIG_ENV_SPI_BUS;
+#else
+	return 0;
+#endif
+}
+
 static int setup_flash_device(struct spi_flash **env_flash)
 {
 #if CONFIG_IS_ENABLED(DM_SPI_FLASH)
 	struct udevice *new;
 	int	ret;
+	int dev = spi_get_env_dev();
 
 	/* speed and mode will be read from DT */
-	ret = spi_flash_probe_bus_cs(CONFIG_ENV_SPI_BUS, CONFIG_ENV_SPI_CS,
+	ret = spi_flash_probe_bus_cs(dev, CONFIG_ENV_SPI_CS,
 				     &new);
 	if (ret) {
 		env_set_default("spi_flash_probe_bus_cs() failed", 0);

include/spi.h

@@ -743,4 +743,6 @@ int dm_spi_get_mmap(struct udevice *dev, ulong *map_basep, uint *map_sizep,
 #define spi_get_ops(dev)	((struct dm_spi_ops *)(dev)->driver->ops)
 #define spi_emul_get_ops(dev)	((struct dm_spi_emul_ops *)(dev)->driver->ops)
 
+int spi_get_env_dev(void);
+
 #endif	/* _SPI_H_ */