On Wed, May 16, 2018 at 2:52 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > On 02/05/18 02:47, Evan Green wrote: > > For a controller with SDHCI_QUIRK_NO_CARD_NO_RESET, there are several > > conditions where sdhci_do_reset is called under a spinlock with interrupts > > disabled. The card detect is often a GPIO, which might sleep. Avoid > > asking for the card detect status if interrupts are disabled to prevent > > a warning like the following: > > > > [ 2.480199] Call trace: > > [ 2.480218] [<ffffff800808a698>] dump_backtrace+0x0/0x228 > > [ 2.480224] [<ffffff800808a8e0>] show_stack+0x20/0x28 > > [ 2.480235] [<ffffff80088a0214>] dump_stack+0x90/0xb0 > > [ 2.480245] [<ffffff80080d7aa8>] ___might_sleep+0x110/0x128 > > [ 2.480248] [<ffffff80080d7b38>] __might_sleep+0x78/0x88 > > [ 2.480260] [<ffffff80083cdd28>] gpiod_get_raw_value_cansleep+0x2c/0xc4 > > [ 2.480269] [<ffffff80086a93a8>] mmc_gpio_get_cd+0x3c/0x68 > > [ 2.480275] [<ffffff80086b008c>] sdhci_get_cd+0x20/0x98 > > [ 2.480280] [<ffffff80086b081c>] sdhci_do_reset+0x50/0x88 > > [ 2.480283] [<ffffff80086b4640>] sdhci_tasklet_finish+0x1a8/0x270 > > [ 2.480292] [<ffffff80080b29d4>] tasklet_action+0x90/0xf4 > > [ 2.480296] [<ffffff80080813b8>] __do_softirq+0x1c8/0x360 > > [ 2.480300] [<ffffff80080b2408>] irq_exit+0x88/0xd0 > > > > --- > > > > I discovered this warning while trying to bring up SD, somewhat unsuccessfully, > > on a new device, and hit this error path. > > > > This change is not ideal as it only makes a best effort to adhere to the quirk, > > but may in some cases end up resetting the controller with no card present. > > > > Another option I considered was trying to call sdhci_do_reset within only > > sleepable contexts. I actually got as far as converting the tasklet to a > > work queue, and deferring the reset to the end of the function in > > sdhci_request_done. But 1) I'm not sure if that deferral was actually safe, > > and 2) we call sdhci_do_reset from under the lock in several other places, > > such as sdhci_card_event and sdhci_cqe_disable. > > > > Finally, I also considered calling the non-_maysleep gpio functions in > > mmc_gpio_get_cd. I assume this is not workable as someone somewhere has put > > a card detect off of a PMIC or GPIO expander. > > > > Any advice? > The SDHCI_QUIRK_NO_CARD_NO_RESET quirk was designed for host controllers > that use the present state register. I have to assume that users of GPIO > card detect get away with using the quirk because: > a) their GPIO does not sleep, and > b) they don't enable the debugging that produces the "might sleep" > warning > If you know your device's card detect GPIO does not sleep, then you can look > at making a non-sleep version of mmc_gpio_get_cd(). > Another possibility is to look at using mmc_gpio_set_cd_isr() to keep track > of whether the card has been removed. Also try to use sdhci_ops->reset() > rather than SDHCI_QUIRK_NO_CARD_NO_RESET. Thanks Adrian for the guidance. I'll explore this a bit and see what shakes out. -Evan -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
