Hi Simon and Fabio,
On 9/12/22 3:16 PM, Simon Glass wrote:
Hi,
On Mon, 12 Sept 2022 at 12:48, Fabio Estevam <feste...@gmail.com> wrote:
Hi Nate and Simon,
On Mon, Sep 12, 2022 at 2:55 PM Nate Drude <nat...@variscite.com> wrote:
gpio_hog_probe_all is invoked by init_sequence_r in board_r.c.
If device_probe fails for any gpio-hog, boot hangs with the following error:
initcall sequence 00000000fffc8e18 failed at call 000000004023b320 (err=-121)
### ERROR ### Please RESET the board ###
gpio-hog-optional allows the boot sequence to continue if device_probe
fails for optional gpio-hog(s).
Signed-off-by: Nate Drude <nat...@variscite.com>
---
doc/device-tree-bindings/gpio/gpio.txt | 1 +
drivers/gpio/gpio-uclass.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/doc/device-tree-bindings/gpio/gpio.txt
b/doc/device-tree-bindings/gpio/gpio.txt
index 1481ed607d..02d296316b 100644
--- a/doc/device-tree-bindings/gpio/gpio.txt
+++ b/doc/device-tree-bindings/gpio/gpio.txt
@@ -189,6 +189,7 @@ gpio-controller's driver probe function.
Each GPIO hog definition is represented as a child node of the GPIO
controller.
Required properties:
- gpio-hog: A property specifying that this child node represents a GPIO
hog.
+- gpio-hog-optional: A property specifying to continue boot when device_probe
fails in gpio_hog_probe_all
gpio-hog-optional property does not exist in Linux.
If this property is introduced then U-Boot and Linux devicetrees will
not be in sync.
Can this be fixed differently?
Nate, can you send a patch to Linux with the binding update?
Regards,
Simon
Thanks for your responses and feedback.
I don't think gpio-hog-optional is relevant to Linux.
The problem is if gpio_hog_probe_all returns an error, board_init_r will
hang()
See:
- https://github.com/u-boot/u-boot/blob/v2022.07/common/board_r.c#L824-L825
- https://github.com/u-boot/u-boot/blob/v2022.07/common/board_r.c#L763
-
https://github.com/u-boot/u-boot/blob/v2022.07/drivers/gpio/gpio-uclass.c#L330-L332
A practical example of how this may occur is when an i2c gpio expander
(e.g. nxp,pca9534) uses gpio-hog, but the gpio expander is depopulated.
Arguably, the best solution is to use a different device tree when the
gpio expander is not populated. This patch allows the gpio-hog to fail
gracefully and continue booting if gpio-hog-optional is used.
Do you have any suggestions for a better approach? Does it make sense
for gpio_hog_probe_all to cause a fatal error when the gpio hog probe
fails (most devices, including the gpio-expander, will not cause a hang
if they fail to probe)?
Regards,
Nate
