Re: [PATCH v4] arm64: dts: rockchip: Fix SD card init on rk3399-nanopi4

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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




[Index of Archives]     [Linux Memonry Technology]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux