[PATCH v2 6/6] doc: spl: Add info regarding memory reservation and missing Kconfigs

[Devarsh Thakkar <devarsht@ti.com>]

Add information regarding memory reservation scheme in SPL
and details regarding scheme which need to be followed while reserving
those areas which need to be preserved across bootstages.

Also add missing CONFIG_SPL Kconfigs and new ones which were added
recently.

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
---
V1->V3 : No change
---
 doc/develop/spl.rst | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/doc/develop/spl.rst b/doc/develop/spl.rst
index 76e87f07c7..fc570589eb 100644
--- a/doc/develop/spl.rst
+++ b/doc/develop/spl.rst
@@ -65,6 +65,15 @@ CONFIG_SPL_NAND_LOAD (drivers/mtd/nand/raw/nand_spl_load.o)
 CONFIG_SPL_SPI_LOAD (drivers/mtd/spi/spi_spl_load.o)
 CONFIG_SPL_RAM_DEVICE (common/spl/spl.c)
 CONFIG_SPL_WATCHDOG (drivers/watchdog/libwatchdog.o)
+CONFIG_SPL_SYSCON (drivers/core/syscon-uclass.o)
+CONFIG_SPL_GZIP (lib/gzip.o)
+CONFIG_SPL_VIDEO (drivers/video/video-uclass.o drivers/video/vidconsole-uclass.o)
+CONFIG_SPL_SPLASH_SCREEN (common/splash.o)
+CONFIG_SPL_SPLASH_SOURCE (common/splash_source.o)
+CONFIG_SPL_GPIO (drivers/gpio)
+CONFIG_SPL_DM_GPIO (drivers/gpio/gpio-uclass.o)
+CONFIG_SPL_BMP (drivers/video/bmp.o)
+CONFIG_SPL_BLOBLIST (common/bloblist.o)
 
 Adding SPL-specific code
 ------------------------
@@ -164,3 +173,16 @@ cflow will spit out a number of warnings as it does not parse
 the config files and picks functions based on #ifdef.  Parsing the '.i'
 files instead introduces another set of headaches.  These warnings are
 not usually important to understanding the flow, however.
+
+
+Reserving memory in SPL
+-----------------------
+
+If memory need to be reserved in RAM during SPL stage so that area won't get touched
+by SPL and/or u-boot, it need to be reserved starting from end of RAM.
+
+Also the regions which are to be preserved across further stages of boot need to be reserved first starting from
+framebuffer memory which must be reserved from end of RAM for which helper function spl_reserve_video_from_ram_top is provided.
+
+The corresponding information of reservation for those regions can be passed to further stages of boot using a bloblist.
+For e.g. the information for framebuffer area reserved by SPL can be passed onto u-boot using BLOBLISTT_U_BOOT_VIDEO.
-- 
2.34.1