On Wed, Jul 14, 2021 at 11:56 AM Stephan Gerhold stephan@gerhold.net wrote:

At the moment pressing the volume down key does not actually launch fastboot. This is because setting "bootdelay" to "-1" actually disables autoboot and drops to the U-Boot console. It does not execute the "bootcmd".

The correct value for "bootdelay" here would be "-2", which disables the delay and key checking and would immediately execute the "bootcmd".

However, even better in this case is using "preboot" to trigger Fastboot. The advantage is that running "fastboot continue" will actually continue the autoboot process instead of ending up in the U-Boot shell.

Also make sure to unset "preboot" again immediately in case the user saves the environment after triggering fastboot.

Cc: Ramon Fried rfried.dev@gmail.com Fixes: aa043ee91a47 ("db410c: automatically launch fastboot") Signed-off-by: Stephan Gerhold stephan@gerhold.net

---

board/qualcomm/dragonboard410c/dragonboard410c.c | 3 +-- configs/dragonboard410c_defconfig | 1 + 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/board/qualcomm/dragonboard410c/dragonboard410c.c b/board/qualcomm/dragonboard410c/dragonboard410c.c index 3b71881cac..371b3262f8 100644 --- a/board/qualcomm/dragonboard410c/dragonboard410c.c +++ b/board/qualcomm/dragonboard410c/dragonboard410c.c @@ -132,8 +132,7 @@ int misc_init_r(void) }

    if (dm_gpio_get_value(&resin)) {

•           env_set("bootdelay", "-1");
  

•           env_set("bootcmd", "fastboot 0");
  

•           env_set("preboot", "setenv preboot; fastboot 0");
            printf("key_vol_down pressed - Starting fastboot.\n");
    }
  
  

diff --git a/configs/dragonboard410c_defconfig b/configs/dragonboard410c_defconfig index dc9d0d893c..a46283f980 100644 --- a/configs/dragonboard410c_defconfig +++ b/configs/dragonboard410c_defconfig @@ -10,6 +10,7 @@ CONFIG_DISTRO_DEFAULTS=y # CONFIG_ANDROID_BOOT_IMAGE is not set CONFIG_FIT=y CONFIG_OF_BOARD_SETUP=y +CONFIG_USE_PREBOOT=y # CONFIG_DISPLAY_CPUINFO is not set # CONFIG_DISPLAY_BOARDINFO is not set CONFIG_MISC_INIT_R=y -- 2.32.0

I also noticed that a few days ago, it's strange because it used to work, maybe something changed since I introduced the fastboot support. Reviewed-by: Ramon Fried rfried.dev@gmail.com

On Wed, Jul 14, 2021 at 11:39:34PM +0300, Ramon Fried wrote:

On Wed, Jul 14, 2021 at 11:56 AM Stephan Gerhold stephan@gerhold.net wrote:

...

For some reason, the DragonBoard 410c aborts autoboot immediately if U-Boot is started without LK. It looks like it picks up a single broken character via serial and therefore believes a key was pressed to abort autoboot.

After some debugging, it seems like adding some delay after pinctrl setup but before UART initialization fixes the issue. It's also worth mentioning that unlike when booting from LK, the pinctrl setup is actually necessary when booting U-Boot without LK since UART is broken if the pinctrl line is removed.

I suspect that reconfiguring the pins might take some time to stabilize and if the UART controller is enabled too quickly it will pick up some random noise. Adding a few milliseconds of delay fixes the issue and shouldn't have any other negative side effects.

3ms seems to be the minimum delay required in my tests, use 5ms instead just to be sure.

Signed-off-by: Stephan Gerhold stephan@gerhold.net

drivers/serial/serial_msm.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/serial/serial_msm.c b/drivers/serial/serial_msm.c index d8dd5c1104..ac4d0824b9 100644 --- a/drivers/serial/serial_msm.c +++ b/drivers/serial/serial_msm.c @@ -18,6 +18,7 @@ #include <asm/global_data.h> #include <asm/io.h> #include <linux/compiler.h> +#include <linux/delay.h> #include <dm/pinctrl.h>

/* Serial registers - this driver works in uartdm mode*/ @@ -193,6 +194,9 @@ static int msm_uart_clk_init(struct udevice *dev)

static void uart_dm_init(struct msm_serial_data *priv) {

•   /* Delay initialization for a bit to let pins stabilize if necessary */
  

•   mdelay(5);
  

•   writel(priv->clk_bit_rate, priv->base + UARTDM_CSR);
    writel(0x0, priv->base + UARTDM_MR1);
    writel(MSM_BOOT_UART_DM_8_N_1_MODE, priv->base + UARTDM_MR2);
  

-- 2.32.0

Eh...this is not a nice fix, perhaps just clearing the RX buffer after initialization will work better ?

I don't like it much either but this is the best I came up with even after spending several hours trying to track down the problem. I also tried porting more register initialization from LK, probably even tried clearing the RX buffer again after initialization.

The problem is: In my tests there was no way to get rid of the delay, because the character doesn't show up until a few milliseconds after initialization. What you suggest would only work like this:

<initialize UART> mdelay(5); // Wait for the weird character to show up <clear RX buffer>

Which is not much different (and in fact will take longer) than:

mdelay(5); <initialize UART>

So unfortunately I can't think of a way to get rid of the delay. :(

I'm not sure if this is some strange problem of my DB410c, I'd actually be curious if the problem can also be reproduced on others.

Stephan