spl: Allow CPU drivers to be used in SPL

Add a new Kconfig option to allow CPU drivers to be used in SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

common/spl/Kconfig

@@ -149,6 +149,16 @@ config SPL_SHA256_SUPPORT
 	  SHA256 variant is supported: SHA512 and others are not currently
 	  supported in U-Boot.
 
+config SPL_CPU_SUPPORT
+	bool "Support CPU drivers"
+	depends on SPL
+	help
+	  Enable this to support CPU drivers in SPL. These drivers can set
+	  up CPUs and provide information about them such as the model and
+	  name. This can be useful in SPL since setting up the CPUs earlier
+	  may improve boot performance. Enable this option to build the
+	  drivers in drivers/cpu as part of an SPL build.
+
 config SPL_CRYPTO_SUPPORT
 	bool "Support crypto drivers"
 	depends on SPL

drivers/Makefile

@@ -10,6 +10,7 @@ obj-$(CONFIG_$(SPL_)RAM)	+= ram/
 
 ifdef CONFIG_SPL_BUILD
 
+obj-$(CONFIG_SPL_CPU_SUPPORT) += cpu/
 obj-$(CONFIG_SPL_CRYPTO_SUPPORT) += crypto/
 obj-$(CONFIG_SPL_I2C_SUPPORT) += i2c/
 obj-$(CONFIG_SPL_GPIO_SUPPORT) += gpio/