[PATCH] dts: qcom: remove hardcoded memory maps

[Varadarajan Narayanan]

On Wed, Jul 01, 2026 at 12:19:33PM +0200, Casey Connolly wrote:
> Qualcomm boards have traditionally relied on a prior bootloader stage
> to populate the memory map in devicetree, and when that wasn't available
> the memory map would instead be hardcoded.
>
> With proper support for SMEM in U-Boot the memory map can now
> dynamically be read out of the SMEM database which is populated on boot
> by the preloader (sbl1).
>
> Switch over all the boards that previously relied on hardcoded memory
> maps to use SMEM instead. This has been tested on the Rubik Pi 3 and
> db410c however other platforms still need testing (see below).
>
> This affects the following boards:
>
> * IPQ5424 RDP466
> * IPQ9574 RDP433
> * QCS615 Ride
> * QCS6490 RB3 Gen 2
> * QCS8300 Ride
> * QCS9100 Ride
>
> Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
> ---
> This patch is based on the qcom-next branch found on the Qualcomm U-Boot
> Custodian repository [1]. For testing please check out that branch,
> apply this patch and then build/boot U-Boot. Ensure that you have
> CONFIG_LOGLEVEL set to >=6 and look for the "Memory map loaded from"
> message during boot, it should say SMEM.
>
> If nothing is broken in U-Boot and Linux then please send your Tested-by
> indicating which board(s) you tried as a "#" comment after your email.
>
> [1]: https://source.denx.de/u-boot/custodians/u-boot-snapdragon
>
> Cc: u-boot-qcom at groups.io
> Cc: Neil Armstrong <neil.armstrong at linaro.org>
> Cc: Sumit Garg <sumit.garg at kernel.org>
> Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>

This fails to boot on both IPQ5424 RDP466 and IPQ9574 RDP433.

IPQ SoCs have the following node in their DTs under reserved-memory.

	$ grep bootloader@ dts/upstream/src/arm64/qcom/*
	dts/upstream/src/arm64/qcom/ipq5018.dtsi:	bootloader at 4a800000 {
	dts/upstream/src/arm64/qcom/ipq5332.dtsi:	bootloader at 4a100000 {
	dts/upstream/src/arm64/qcom/ipq5424.dtsi:	bootloader at 8a200000 {
	dts/upstream/src/arm64/qcom/ipq6018.dtsi:	bootloader at 4a100000 {
	dts/upstream/src/arm64/qcom/ipq8074.dtsi:	bootloader at 4a600000 {
	dts/upstream/src/arm64/qcom/ipq9574.dtsi:	bootloader at 4a100000 {

While booting, initr_caches -> enable_caches -> configure_reserved_memory
unmaps the above 'bootloader' reserved-memory region. Eventually, when
U-Boot looks for environment variables via env_get_f(), the 'env' pointer
points inside the 'bootloader' region. Since it has been unmapped, it
crashes.

diff --git a/arch/arm/mach-snapdragon/mem_map.c b/arch/arm/mach-snapdragon/mem_map.c
index f64ec0c674e..d554537fbec 100644
--- a/arch/arm/mach-snapdragon/mem_map.c
+++ b/arch/arm/mach-snapdragon/mem_map.c
@@ -112,6 +112,10 @@ static void configure_reserved_memory(void)
        fdt_for_each_subnode(rmem, gd->fdt_blob, parent) {
                const fdt32_t *ptr;
                attrs = PTE_TYPE_FAULT;
+
+               if (!memcmp("bootloader@", fdt_get_name(gd->fdt_blob, rmem, NULL), 11))
+                       continue;
+
                /* If the no-map property isn't set then the region is valid */
                if (!fdt_getprop(gd->fdt_blob, rmem, "no-map", NULL))
                        attrs = PTE_TYPE_VALID | PTE_BLOCK_MEMTYPE(MT_NORMAL);

Thanks
Varada