[PATCH 2/2] docs: firmware: Document parameters passed to firmware and alignment requirement

[Bin Meng]

This updates documentation to describe parameters passed to firmware
from previous booting stage, and corresponding address alignment
requirement.

This also fixes a typo in fw_dynamic.md (it's => its).

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
---

 docs/firmware/fw.md         | 7 +++++++
 docs/firmware/fw_dynamic.md | 5 +++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/docs/firmware/fw.md b/docs/firmware/fw.md
index cc0cc9e..a3bb70c 100644
--- a/docs/firmware/fw.md
+++ b/docs/firmware/fw.md
@@ -9,6 +9,13 @@ OpenSBI generic library code. The supported firmwares type will differ in how
 the arguments passed by the platform early boot stage are handled, as well as
 how the boot stage following the firmware will be handled and executed.
 
+The previous booting stage will pass information via the following registers
+of RISC-V CPU:
+
+* hartid via *a0* register
+* device tree blob address in memory via *a1* register. The address must be
+  aligned to 8 bytes.
+
 OpenSBI currently supports three different types of firmwares.
 
 Firmware with Dynamic Information (*FW_DYNAMIC*)
diff --git a/docs/firmware/fw_dynamic.md b/docs/firmware/fw_dynamic.md
index 01f43f9..7b9b192 100644
--- a/docs/firmware/fw_dynamic.md
+++ b/docs/firmware/fw_dynamic.md
@@ -6,8 +6,9 @@ information about next booting stage (e.g. a bootloader or an OS) and runtime
 OpenSBI library options from previous booting stage.
 
 The previous booting stage will pass information to *FW_DYNAMIC* by creating
-*struct fw_dynamic_info* in memory and passing it's address to *FW_DYNAMIC*
-via *a2* register of RISC-V CPU.
+*struct fw_dynamic_info* in memory and passing its address to *FW_DYNAMIC*
+via *a2* register of RISC-V CPU. The address must be aligned to 8 bytes on
+RV64 and 4 bytes on RV32.
 
 A *FW_DYNAMIC* firmware is particularly useful when the booting stage executed
 prior to OpenSBI firmware is capable of loading both the OpenSBI firmware and
-- 
2.25.1