Hi,
On 6/1/23 01:09, Marek Vasut wrote:
On 5/26/23 17:28, patrick.delaunay@xxxxxxxxxxx wrote:
Hi Marek,
Hi,
From: Marek Vasut <marex@xxxxxxx>
Sent: Wednesday, May 17, 2023 5:25 PM
Subject: [PATCH v2 3/3] ARM: dts: stm32: Add nvmem-syscon node to
TAMP to
expose boot count on DHSOM
Add nvmem-syscon subnode to expose TAMP_BKPxR register 19 to user
space.
This register contains U-Boot boot counter, by exposing it to user
space the user
space can reset the boot counter.
Read access example:
"
$ hexdump -vC /sys/bus/nvmem/devices/5c00a000.tamp\:nvmem0/nvmem
00000000 0c 00 c4 b0
"
Signed-off-by: Marek Vasut <marex@xxxxxxx>
---
Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>
Cc: Conor Dooley <conor+dt@xxxxxxxxxx>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>
Cc: Marek Vasut <marex@xxxxxxx>
Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: kernel@xxxxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
V2: No change
---
arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi | 11 +++++++++++
arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi | 11 +++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
b/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
index 74735552f4803..b2557bb718f52 100644
--- a/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
+++ b/arch/arm/boot/dts/stm32mp15xx-dhcom-som.dtsi
@@ -537,6 +537,17 @@ &sdmmc3 {
status = "okay";
};
+&tamp {
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ /* Boot counter */
+ nvmem {
+ compatible = "nvmem-syscon";
+ reg = <0x14c 0x4>;
+ };
+};
+
&uart4 {
pinctrl-names = "default";
pinctrl-0 = <&uart4_pins_a>;
diff --git a/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
b/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
index bba19f21e5277..864960387e634 100644
--- a/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
+++ b/arch/arm/boot/dts/stm32mp15xx-dhcor-som.dtsi
@@ -269,3 +269,14 @@ &rng1 {
&rtc {
status = "okay";
};
+
+&tamp {
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ /* Boot counter */
+ nvmem {
According binding you need to add "@<reg>" => nvmem@14c
And you export only TAMP_BKP19R directly in a nvmem region ?
4 bytes is more than plenty for boot counter , yes.
+ compatible = "nvmem-syscon";
+ reg = <0x14c 0x4>;
+ };
+};
the boot counter could be a nvem cell so you could expose other
backup registers
For example :
&tamp {
#address-cells = <1>;
#size-cells = <1>;
nvmem@14c {
compatible = "nvmem-syscon";
reg = <0x14c 0x4>;
/* Data cells */
boot_counter: boot-counter@14c {
reg = <0x14c 0x4>;
};
};
};
Even if you export more backup register the cell will be correctly
described in DT
and could be accessible directly with sysfs without managed offset
in userland
with https://lore.kernel.org/lkml/202305240724.z3McDuYM-lkp@xxxxxxxxx/T/
Or previous serie
https://lore.kernel.org/lkml/20211220064730.28806-1-zajec5@xxxxxxxxx/
for example to export all the free register:
Reference: https://wiki.st.com/stm32mpu/wiki/STM32MP15_backup_registers
the cell " boot-counter" will be always available for users.
&tamp {
#address-cells = <1>;
#size-cells = <1>;
/* backup register: 10 to 21 */
nvmem@0x128 {
compatible = "nvmem-syscon";
reg = <0x128 0x44>;
/* Data cells */
boot_counter: boot-counter@14c {
reg = <0x14c 0x4>;
};
boot_mode: boot-mode@150 {
reg = <0x150 0x4>;
};
....
};
};
Sure, thanks. I'm not sure I understood the message above.
sorry if it wasn't clear
TAMP register a nvmem driver = NVRAM provider
=> it should export ALL the free backup registers
as they can used by application / kernel for many purpose....
and not only for boot counterfor you use-case
So limit the exported backup register to this 4 bytes is strange for me.
and COUNTER is a nvem cell = a part of backup register = TAMP_BKP19R
=> I agree 4 byte for this count is fine for this cell
NB: today we have no means to read only one nvmem cell with sysfs API
but I see this feature is proposed to have something as
/sys/bus/nvmem/devices/nvmem@0x128/ => all the backup registers
/sys/bus/nvmem/devices/nvmem@0x128/cells/boot-mode => only the nvmem
cell used as counter I think it is more safe for long term support to
manage your counter as a nvmem cell. regards Patrick
