Hi Sumit,
On 5/12/25 08:01, Sumit Garg wrote:
On Fri, May 09, 2025 at 04:54:43PM +0200, Stephan Gerhold wrote:
On Fri, May 09, 2025 at 12:45:20PM +0200, Casey Connolly wrote:
On 5/8/25 12:32, Sumit Garg wrote:
From: Sumit Garg <sumit.g...@oss.qualcomm.com>
When debug serial port isn't connected, it is at least reported on RB1
that autoboot gets interrupted. It is probably due to random characters
on the UART RX line when disconnected. Lets try to fix this inconsistent
behaviour via enabling AUTOBOOT_KEYED such that the autoboot gets
interrupted only when the <SPACE> key gets pressed.
Honestly I'd much rather fix the bug in the UART driver, maybe it's broken
pinctrl?
The older UART driver (for msm8916) had a similar but that Stephen was able
to fix with better configuration.
Anyhow, this is a sensible enough workaround if nobody wants to look into
GENI...
Well, the main fix I did for that isn't related to the UART driver at
all, it's simply adding bias-pull-up for the RX pin so that it isn't
left floating when UART is not connected.
For RB1, qcm2290.dtsi &qup_uart4_default currently has bias-disable for
both RX and TX pins. So please try applying bias-pull-up + bootph-all
for the GPIO that belongs to RX.
For details, please see the following patch series for MSM8916:
https://lore.kernel.org/linux-arm-msm/20250422-msm8916-console-pinctrl-v2-0-f345b7a53...@linaro.org/T/
Thanks for this reference but unfortunately this doesn't fix the issue
on RB1. I have tried the diff below [1]. It seems most likely due the
chainloading via ABL on RB1 as compared to U-Boot running as primary
bootloader on db410c. The RX line seems to be floating even before the
U-Boot starts which is causing the autoboot to stop. So for the
chainloading configuration, we need to enable AUTOBOOT_KEYED. I think
it should be the default sane configuration on Qcom platforms rather
than allowing autoboot stopped via any random character on RX line.
I dug into it and the rogue inputs actually come from the button-kbd
driver, maybe the buttons are slightly misconfigured. This explains why
it only happens on some boards.
So the right solution here is to fix the buttons, or disable button-kbd
if you don't need it.
Kind regards,
[1]
diff --git a/dts/upstream/src/arm64/qcom/qcm2290.dtsi
b/dts/upstream/src/arm64/qcom/qcm2290.dtsi
index f0746123e59..9392bd6f3e0 100644
--- a/dts/upstream/src/arm64/qcom/qcm2290.dtsi
+++ b/dts/upstream/src/arm64/qcom/qcm2290.dtsi
@@ -551,10 +551,28 @@
};
qup_uart4_default: qup-uart4-default-state {
+ tx-pins {
+ pins = "gpio12";
+ function = "qup4";
+ drive-strength = <16>;
+ bias-disable;
+ bootph-all;
+ };
+
+ rx-pins {
+ pins = "gpio13";
+ function = "qup4";
+ drive-strength = <16>;
+ bias-pull-up;
+ bootph-all;
+ };
+ };
+
+ qup_uart4_sleep: qup-uart4-sleep-state {
pins = "gpio12", "gpio13";
- function = "qup4";
+ function = "gpio";
drive-strength = <2>;
- bias-disable;
+ bias-pull-down;
};
sdc1_state_on: sdc1-on-state {
@@ -1293,7 +1311,8 @@
clocks = <&gcc GCC_QUPV3_WRAP0_S4_CLK>;
clock-names = "se";
pinctrl-0 = <&qup_uart4_default>;
- pinctrl-names = "default";
+ pinctrl-1 = <&qup_uart4_sleep>;
+ pinctrl-names = "default", "sleep";
interconnects = <&qup_virt MASTER_QUP_CORE_0
RPM_ALWAYS_TAG
&qup_virt SLAVE_QUP_CORE_0
RPM_ALWAYS_TAG>,
<&bimc MASTER_APPSS_PROC
RPM_ALWAYS_TAG
-Sumit
--
Casey (she/they)
