On 2022-07-15 18:16, Christian Kohlschütter wrote:
OK, this took me a while to figure out.
When no undervoltage limit is configured, I can reliably trigger the initialization bug upon boot.
When the limit is set to 3.0V, it rarely occurs, but just after I send the v3 patch, I was able to reproduce...
Well this has to be in the running for "weirdest placebo ever"... :/
All it actually seems to achieve is printing an error[1] (this is after
all a tiny 5-pin fixed-voltage LDO regulator, not an intelligent PMIC),
and if that makes an appreciable difference then there has to be some
kind of weird timing condition at play. Maybe regulator_register() ends
up turning it off and on again rapidly enough that the card sees a
voltage brownout and glitches, and adding more delay by printing to the
console somewhere in the middle gives it enough time to act as a proper
power cycle with no ill effect?
If you just whack something like an mdelay(500) at around that point in
set_machine_constraints(), without the DT property, does it have the
same effect?
Robin.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/regulator/core.c#n1521
Am 15.07.2022 um 19:12 schrieb Christian Kohlschütter <christian@xxxxxxxxxxxxxxxx>:
mmc/SD-card initialization may fail on NanoPi R4S with
"mmc1: problem reading SD Status register" /
"mmc1: error -110 whilst initialising SD card"
either on cold boot or after a reboot.
Moreover, the system would also sometimes hang upon reboot.
This is prevented by setting an explicit undervoltage protection limit
for the SD-card-specific vcc3v0_sd voltage regulator.
Set the undervoltage protection limit to 2.7V, which is the minimum
permissible SD card operating voltage.
Signed-off-by: Christian Kohlschütter <christian@xxxxxxxxxxxxxxxx>
---
arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi | 4 ++++
1 file changed, 4 insertions(+)
mode change 100644 => 100755 arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
diff --git a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
old mode 100644
new mode 100755
index 8c0ff6c96e03..669c74ce4d13
--- a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
@@ -73,6 +73,10 @@ vcc3v0_sd: vcc3v0-sd {
regulator-always-on;
regulator-min-microvolt = <3000000>;
regulator-max-microvolt = <3000000>;
+
+ // must be configured or SD card may fail to initialize occasionally
+ regulator-uv-protection-microvolt = <2700000>;
+
regulator-name = "vcc3v0_sd";
vin-supply = <&vcc3v3_sys>;
};
--
2.36.1
