Hi,
Today I tried to run barebox with CONFIG_KEYBOARD_GPIO=y added to my config.
and noticed my board hangs during boot. When I modify the probe function to
run without registering the poller[1] it boots as expected.
I started digging into the code to see how far the boot gets when I do
register the poller. I found that Barebox hangs in a do/while loop in
sdhci_transfer_data_dma[2].
The contents of the interrupt status (SDHCI_INT_STATUS) is 0 and stays that
way forever trapping the process in the loop.
Call stack:
initcall -> barebox_of_populate
state_probe drivers/misc/state.c
state_new_from_node common/state/state.c
of_find_path_by_node drivers/of/of_path.c
__of_find_path drivers/of/of_path.c
device_detect drivers/base/driver.c
mci_detect_card drivers/mci/mci-core.c
mci_card_probe drivers/mci/mci-core.c
mci_startup drivers/mci/mci-core.c
mci_startup_mmc drivers/mci/mci-core.c
mmc_compare_ext_csds drivers/mci/mci-core.c
mci_send_ext_csd drivers/mci/mci-core.c
mci_send_cmd drivers/mci/mci-core.c
esdhc_send_cmd
drivers/mci/imx-esdhc.c
__esdhc_send_cmd
drivers/mci/imx-esdhc-common.c
sdhci_transfer_data_dma drivers/mci/sdhci.c
I'm not sure how this happens. It's not the first transfer taking place. I
figured that mayby the poller[1] just adds some cpu load that opens up a
window for this to occur.
Maybe something else cleared the status register right before we entered the
loop. Thats when I spotted this read/write construction[3]. It's executed
right before we enter the do/while loop and (over)writes to the irq status
register.
I removed the line with the write command[3] and my board boots as expected.
Why are we (over)writing the status register right after reading it?
Other theories on how this could occur are also very welcome :)
- Robin
1:
https://git.pengutronix.de/cgit/barebox/tree/drivers/input/gpio_keys.c#n168
2: https://git.pengutronix.de/cgit/barebox/tree/drivers/mci/sdhci.c#n167
3:
https://git.pengutronix.de/cgit/barebox/tree/drivers/mci/imx-esdhc-common.c#n179
