* [PATCH] arm64: dts: mediatek: mt7986a-bananapi-bpi-r3: add ramoops region
@ 2026-05-28 9:30 Martino Dell'Ambrogio
2026-05-28 12:36 ` [PATCH v2] arm64: dts: mediatek: mt7988a-bananapi-bpi-r4: " Martino Dell'Ambrogio
0 siblings, 1 reply; 2+ messages in thread
From: Martino Dell'Ambrogio @ 2026-05-28 9:30 UTC (permalink / raw)
To: matthias.bgg, angelogioacchino.delregno
Cc: kees, tony.luck, gpiccoli, linux-mediatek, linux-arm-kernel,
devicetree, linux-kernel, Martino Dell'Ambrogio
Reserve 64 KiB of RAM just below the ARM Trusted Firmware secmon region
(0x42ff0000-0x43000000) for persistent kernel log storage via pstore/ramoops,
allowing post-panic console output and oops dumps to be recovered after a
warm reset. Without it, kernel crash logs on this board are lost when the
SoC reboots.
The carve-out is divided into 8 KiB kmsg records, a 32 KiB rolling console,
8 KiB ftrace, and 8 KiB pmsg, leaving the remainder for the per-record
Reed-Solomon ECC parity (ecc-size=16) which significantly improves dump
readability when the panic path truncates writes mid-record.
The region sits immediately below the ATF block already declared at
0x43000000 in mt7986a.dtsi, so no other reserved-memory child is moved or
resized. BPI-R3 ships with 2 GiB of DRAM starting at 0x40000000, well above
0x43000000, so the region is always within installed memory.
For the carve-out to actually preserve content across a reset, the boot
loader must avoid touching this region on warm reset; on standard BPI-R3
boards with the stock OpenWrt U-Boot fork this already holds.
Signed-off-by: Martino Dell'Ambrogio <tillo@tillo•ch>
---
.../boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
index 19f538d..31ee189 100644
--- a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
+++ b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
@@ -140,6 +140,18 @@ sfp2: sfp-2 {
};
};
+&{/reserved-memory} {
+ ramoops@42ff0000 {
+ compatible = "ramoops";
+ reg = <0 0x42ff0000 0 0x10000>;
+ record-size = <0x2000>;
+ console-size = <0x8000>;
+ ftrace-size = <0x2000>;
+ pmsg-size = <0x2000>;
+ ecc-size = <16>;
+ };
+};
+
&cpu_thermal {
cooling-maps {
map-cpu-active-high {
--
2.47.3
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH v2] arm64: dts: mediatek: mt7988a-bananapi-bpi-r4: add ramoops region
2026-05-28 9:30 [PATCH] arm64: dts: mediatek: mt7986a-bananapi-bpi-r3: add ramoops region Martino Dell'Ambrogio
@ 2026-05-28 12:36 ` Martino Dell'Ambrogio
0 siblings, 0 replies; 2+ messages in thread
From: Martino Dell'Ambrogio @ 2026-05-28 12:36 UTC (permalink / raw)
To: matthias.bgg, angelogioacchino.delregno
Cc: kees, tony.luck, gpiccoli, linux-mediatek, linux-arm-kernel,
devicetree, linux-kernel, Martino Dell'Ambrogio
Reserve 1 MiB of RAM just below the ARM Trusted Firmware secmon region
(0x42f00000-0x43000000) for persistent kernel log storage via pstore/ramoops,
allowing post-panic console output and oops dumps to be recovered after a
reboot. Without it, kernel crash logs on this board are lost when the SoC
warm-resets and the on-chip console buffer is reinitialised.
With record-size=128 KiB, console-size=256 KiB, ftrace-size=64 KiB and
pmsg-size=64 KiB, ramoops_probe() carves the post-console remainder
(640 KiB) into five 128 KiB kmsg records, with the requested ecc-size=16
reserving a small Reed-Solomon parity block from each zone's own
allocation (per persistent_ram_new()). The ECC lets pstore recover dumps
even when the panic path truncates writes mid-record.
The no-map property is required so the reserved region is kept out of the
kernel linear map. ramoops remaps the carve-out write-combine via
ioremap_wc(); on arm64, leaving the same physical RAM mapped cacheable in
the linear map at the same time is an attribute-mismatch and risks losing
panic data to dirty cache evictions from the linear alias.
The carve-out sits immediately below the ATF region already declared at
0x43000000 in mt7988a.dtsi, so no other reserved-memory child is moved or
resized. BPI-R4 ships with at least 4 GiB of DRAM starting at 0x40000000,
so the region is well within installed memory on every variant.
For the carve-out to actually preserve content across a reset, the boot
loader must also avoid touching this region on warm reset; on standard
BPI-R4 boards with the stock OpenWrt U-Boot fork this already holds.
Signed-off-by: Martino Dell'Ambrogio <tillo@tillo•ch>
---
Changes in v2:
- Add no-map; to keep the carve-out out of the kernel linear map and
avoid the cacheable/write-combine attribute mismatch on arm64.
(sashiko-bot, gemini-3.1-pro)
- Rewrite the ECC paragraph in the commit log: ramoops carves ecc-size
from each zone's own allocation in persistent_ram_new() and the
post-console remainder is split into record-size'd kmsg records, not
one record plus a separate ECC pool. (sashiko-bot, gemini-3.1-pro)
v1: https://lore.kernel.org/all/20260528093038.1945245-1-tillo@tillo.ch/
.../boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dtsi | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dtsi b/arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dtsi
index 0ff69da..f7d4944 100644
--- a/arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt7988a-bananapi-bpi-r4.dtsi
@@ -80,6 +80,19 @@ sfp1: sfp1 {
};
};
+&{/reserved-memory} {
+ ramoops@42f00000 {
+ compatible = "ramoops";
+ reg = <0 0x42f00000 0 0x100000>;
+ no-map;
+ record-size = <0x20000>;
+ console-size = <0x40000>;
+ ftrace-size = <0x10000>;
+ pmsg-size = <0x10000>;
+ ecc-size = <16>;
+ };
+};
+
&cci {
proc-supply = <&rt5190_buck3>;
};
--
2.47.3
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2026-05-28 9:30 [PATCH] arm64: dts: mediatek: mt7986a-bananapi-bpi-r3: add ramoops region Martino Dell'Ambrogio
2026-05-28 12:36 ` [PATCH v2] arm64: dts: mediatek: mt7988a-bananapi-bpi-r4: " Martino Dell'Ambrogio
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