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From: Robin van der Gracht <>
To: Barebox <>
Cc: Andrey Smirnov <>
Subject: Boot hangs during sdhci_transfer_data_dma
Date: Mon, 20 Jun 2022 16:33:02 +0200	[thread overview]
Message-ID: <> (raw)


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

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
                               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

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


             reply	other threads:[~2022-06-20 14:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-20 14:33 Robin van der Gracht [this message]
2022-06-21  7:46 ` Sascha Hauer
2022-06-21  9:32   ` Robin van der Gracht
2022-06-21 10:07   ` Robin van der Gracht

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