On 2022-07-15 19:11, Robin Murphy wrote:
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?
...and apparently the answer is yes, it seems to be doing exactly that (see attached). But seemingly my SD cards don't mind, or maybe my T4 board happens to have more capacitance than Christian's R4S so my voltage dip isn't as bad, or both.
So it seems like the solution here might indeed simply be to remove the regulator-always-on which doesn't seem to have any reason to be here anyway. Without that, the enable stays low until the MMC driver probes and claims it, which is then massively longer than the time it takes for VCC3V0_SD to ramp down completely.
Robin.
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#n1521Am 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.dtsidiff --git a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsiold 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_______________________________________________ Linux-rockchip mailing list Linux-rockchip@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-rockchip
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