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firmware: Allow fw_platform_init() to return updated FDT location

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Currently, the fw_platform_init() does not return anything but we can
further improve by allowing fw_platform_init() to return updated FDT
location.

It is certainly not mandatory for fw_platform_init() to return a new
location of FDT (or modify FDT). In fact, the fw_platform_init() can
always return the original FDT location (i.e. 'arg1') unmodified.

This new capability of fw_platform_init() will allow platforms to:
1. Have multiple built-in FDTs and select one
2. Modify FDT before using based on platform specific straps or OTP

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
This commit is contained in:
Anup Patel 2020-05-24 10:03:13 +05:30 • committed by Anup Patel
parent 4ce6b7a82a
commit 86ec5341e4
2 changed files with 12 additions and 4 deletions
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3
firmware/fw_base.S
View file

@ -198,7 +198,9 @@ _prev_arg1_override_done:
*/
MOV_5R s0, a0, s1, a1, s2, a2, s3, a3, s4, a4
call fw_platform_init
add t0, a0, zero
MOV_5R a0, s0, a1, s1, a2, s2, a3, s3, a4, s4
add a1, t0, zero
/* Preload HART details
* s7 -> HART Count
@ -475,6 +477,7 @@ _start_hang:
.globl fw_platform_init
.weak fw_platform_init
fw_platform_init:
add a0, a1, zero
ret
.section .entry, "ax", %progbits

13
platform/generic/platform.c
View file

@ -62,10 +62,14 @@ static u32 generic_hart_index2id[SBI_HARTMASK_MAX_BITS] = { 0 };
* The arguments passed to fw_platform_init() function are boot time state
* of A0 to A4 register. The "arg0" will be boot HART id and "arg1" will
* be address of FDT passed by previous booting stage.
*
* The return value of fw_platform_init() function is the FDT location. If
* FDT is unchanged (or FDT is modified in-place) then fw_platform_init()
* can always return the original FDT location (i.e. 'arg1') unmodified.
*/
void fw_platform_init(unsigned long arg0, unsigned long arg1,
unsigned long arg2, unsigned long arg3,
unsigned long arg4)
unsigned long fw_platform_init(unsigned long arg0, unsigned long arg1,
unsigned long arg2, unsigned long arg3,
unsigned long arg4)
{
const char *model, *mmu_type;
void *fdt = (void *)arg1;
@ -106,7 +110,8 @@ void fw_platform_init(unsigned long arg0, unsigned long arg1,
platform.hart_count = hart_count;
return;
/* Return original FDT pointer */
return arg1;
fail:
while (1)