On 6/4/26 00:27, Sam Day wrote:
Heya Casey,
On Wednesday, 3 June 2026 at 11:47 PM, Casey Connolly
<[email protected]> wrote:
Hi Sam,
(CC list definitely needs some tuning on the next revision XD)
Hmm? Is it incorrect to use `b4 prep --auto-to-cc` nowadays?
Urgh yeah I think this is a U-Boot issue with MAINTAINERS, needs some
improvement but not your fault.
On 6/1/26 10:12, Sam Day via B4 Relay wrote:
From: Sam Day <[email protected]>
Many (often fused) bootloaders on older ARMv7 qcom SoCs do not support
FDTs at all, and instead pass along ATAGS in r2.
Minimal support for parsing memory info out of these tags is introduced,
so that we can support mainline devicetrees, which expect the bootloader
to populate /memory nodes.
I think this should go its own armv7-specific file. It would probably
also make sense to just have a separate implementation of
board_fdt_blob_setup() since it's already really quite complicated.
I was considering that as well but decided against it, since sprinkling #ifdef
everywhere is quite ugly, and the ATAGS handling code is quite minimal. Are you
sure it really needs to be split out?
I would have the two implementations in different files
The SMEM series will do a bit of rework, in the next spin I'll probably
move the caching stuff out as well, maybe I should also take
board_fdt_blob_setup() then the file can be arm64 specific?
I'm not sure how we can have a separate version of board_fdt_blob_setup. On
ARMv7, sometimes you'll br receiving ATAGS in r2, sometimes it'll be FDT. It
depends on which bootloader you're chaining from.
I see, can we impose any limitations on this in practise? If not then I
guess this is fine. I'd like to see all this logic cleaned up a bit as
I'm just worried about introducing bugs
At the very least I'd like it if the atags parsing was moved to a
different file then here we can do if
(CONFIG_IS_ENABLED(...SNAPDRAGON_ARM32)
qcom_parse_atags()
the compiler will optimise out the function call so there's no need for
a stub version
e.g my nokia-fame can run U-Boot directly chained from SBL3 since the bootchain
on this device has been broken enough, in which case U-Boot gets ATAGS. My
samsung-expressltexx chains from lk2nd, in which case U-Boot gets an FDT.
Cheers,
-Sam
Signed-off-by: Sam Day <[email protected]>
---
arch/arm/mach-snapdragon/board.c | 119
++++++++++++++++++++++++++++++---------
1 file changed, 91 insertions(+), 28 deletions(-)
diff --git a/arch/arm/mach-snapdragon/board.c b/arch/arm/mach-snapdragon/board.c
index 627b566d178..753983467a0 100644
--- a/arch/arm/mach-snapdragon/board.c
+++ b/arch/arm/mach-snapdragon/board.c
@@ -11,6 +11,7 @@
#include <asm/gpio.h>
#include <asm/io.h>
+#include <asm/setup.h>
#include <asm/system.h>
#include <dm/device.h>
#include <dm/pinctrl.h>
@@ -175,6 +176,67 @@ static int qcom_parse_memory(const void *fdt)
return 0;
}
+static bool qcom_atags_valid(const phys_addr_t p)
+{
+ const struct tag *tags = (const struct tag *)p;
+
+ return tags && tags->hdr.tag == ATAG_CORE &&
+ tags->hdr.size >= sizeof(struct tag_header) / sizeof(u32);
+}
+
+static int qcom_parse_atags(const struct tag *tags)
+{
+ phys_addr_t ram_end = 0;
+ const struct tag *t;
+ bool atags_end = false;
+ u32 words = 0;
+ int j = 0;
+
+ memset(prevbl_ddr_banks, 0, sizeof(prevbl_ddr_banks));
+
+ for (t = tags; words < SZ_16K / sizeof(u32); t = tag_next(t)) {
+ if (t->hdr.tag == ATAG_NONE) {
+ atags_end = true;
+ break;
+ }
+ if (t->hdr.size < sizeof(struct tag_header) / sizeof(u32))
+ return -EINVAL;
+ if (t->hdr.size > SZ_16K / sizeof(u32) - words)
+ return -EINVAL;
+
+ words += t->hdr.size;
+
+ if (t->hdr.tag != ATAG_MEM)
+ continue;
+ if (t->hdr.size < tag_size(tag_mem32))
+ return -EINVAL;
+ if (!t->u.mem.size)
+ continue;
+
+ prevbl_ddr_banks[j].start = t->u.mem.start;
+ prevbl_ddr_banks[j].size = t->u.mem.size;
+ ram_end = max(ram_end, (phys_addr_t)t->u.mem.start +
t->u.mem.size);
+ j++;
+
+ if (j == CONFIG_NR_DRAM_BANKS)
+ break;
+ }
+
+ if (!atags_end && j < CONFIG_NR_DRAM_BANKS) {
+ log_err("Provided more memory banks than we can handle\n");
+ return -EINVAL;
+ }
+ if (!j)
+ return -ENODATA;
+
+ qsort(prevbl_ddr_banks, j, sizeof(prevbl_ddr_banks[0]), ddr_bank_cmp);
+
+ gd->ram_base = prevbl_ddr_banks[0].start;
+ gd->ram_size = ram_end - gd->ram_base;
+
+ return 0;
+}
+
static void show_psci_version(void)
{
#ifdef CONFIG_ARM64
@@ -227,42 +289,52 @@ static void qcom_psci_fixup(void *fdt)
*/
int board_fdt_blob_setup(void **fdtp)
{
- struct fdt_header *external_fdt, *internal_fdt;
- bool internal_valid, external_valid;
- int ret = -ENODATA;
-
- internal_fdt = (struct fdt_header *)*fdtp;
- external_fdt = (struct fdt_header *)get_prev_bl_fdt_addr();
- external_valid = external_fdt && !fdt_check_header(external_fdt);
- internal_valid = !fdt_check_header(internal_fdt);
+ int ret = -ENODATA, setup_ret = -EEXIST;
+ struct fdt_header *internal_fdt = *fdtp;
+ phys_addr_t prev_bl_arg = get_prev_bl_fdt_addr();
+ bool internal_valid = internal_fdt && !fdt_check_header(internal_fdt);
+ bool external_is_fdt = prev_bl_arg &&
+ !fdt_check_header((const void *)prev_bl_arg);
- /*
- * There is no point returning an error here, U-Boot can't do anything
useful in this situation.
- * Bail out while we can still print a useful error message.
- */
- if (!internal_valid && !external_valid)
+ if (internal_valid) {
+ debug("Using built in FDT\n");
+ } else if (external_is_fdt) {
+ debug("Using external FDT\n");
+ *fdtp = (void *)prev_bl_arg;
+ setup_ret = 0;
+ } else {
+ /*
+ * There is no point returning an error here, U-Boot can't do
+ * anything useful in this situation. Bail out while we can
+ * still print a useful error message.
+ */
panic("Internal FDT is invalid and no external FDT was provided!
(fdt=%p)\n",
- external_fdt);
+ (void *)prev_bl_arg);
+ }
/* Prefer memory information from internal DT if it's present */
if (internal_valid)
ret = qcom_parse_memory(internal_fdt);
- if (ret < 0 && external_valid) {
+ if (ret < 0 && prev_bl_arg) {
/* No internal FDT or it lacks a proper /memory node.
* The previous bootloader handed us something, let's try that.
*/
if (internal_valid)
debug("No memory info in internal FDT, falling back to
external\n");
- ret = qcom_parse_memory(external_fdt);
+ /* the prev BL arg is either an FDT or ATAGS */
+ if (external_is_fdt)
+ ret = qcom_parse_memory((const void *)prev_bl_arg);
+ if (ret < 0 && qcom_atags_valid(prev_bl_arg))
+ ret = qcom_parse_atags((const struct tag *)prev_bl_arg);
}
if (ret < 0)
panic("No valid memory ranges found!\n");
- /* If we have an external FDT, it can only have come from the Android
bootloader. */
- if (external_valid)
+ /* If we have a prev BL arg, we assume it came from ABL */
+ if (prev_bl_arg)
qcom_boot_source = QCOM_BOOT_SOURCE_ANDROID;
else
qcom_boot_source = QCOM_BOOT_SOURCE_XBL;
@@ -270,18 +342,9 @@ int board_fdt_blob_setup(void **fdtp)
debug("ram_base = %#011lx, ram_size = %#011llx\n",
gd->ram_base, (unsigned long long)gd->ram_size);
- if (internal_valid) {
- debug("Using built in FDT\n");
- ret = -EEXIST;
- } else {
- debug("Using external FDT\n");
- *fdtp = external_fdt;
- ret = 0;
- }
-
qcom_psci_fixup(*fdtp);
- return ret;
+ return setup_ret;
}
/*
