Hi Grygorii, > Am 09.06.2017 um 18:25 schrieb Grygorii Strashko <grygorii.strashko@xxxxxx>: > > > > On 06/09/2017 01:05 AM, H. Nikolaus Schaller wrote: >> Hi, >> >>> Am 07.06.2017 um 22:44 schrieb Sebastian Reichel <sre@xxxxxxxxxx>: >>> >>> Hi, >>> >>> On Sun, May 21, 2017 at 12:38:18PM +0200, H. Nikolaus Schaller wrote: >>>> This fixes an issue if both this twl4030_charger driver and >>>> phy-twl4030-usb are compiled as modules and loaded in random order. >>>> It has been observed on GTA04 and OpenPandora devices that in worst >>>> case the boot process hangs and in best case the AC detection fails >>>> with a warning. >>>> >>>> Therefore we add deferred probing checks for the usb_phy and the >>>> iio channel for AC detection. >>>> >>>> For implementing this we must reorder code because we can't safely >>>> return -EPROBE_DEFER after allocating any devm managed interrupt >>>> (it might already/still be enabled without working interrupt handler). >>>> >>>> So the check for required resources that may abort probing by >>>> returning -EPROBE_DEFER, must come first. >>> >>> This sounds fishy. EPROBE_DEFER should not be different from >>> other error codes in this regard and devm_ requested resources >>> should be free'd on any error. Why is irq handler not working? >> >> 1. there is no other error code involved, before we try to convert the driver to handle EPROBE_DEFER. >> So it is not that EPROBE_DEFER is special but that we add an error return path for it. >> >> 2. I don't know why it is not working - I just know that the handler seems to be triggered before >> all resources are available (if probe() is aborted with EPROBE_DEFER error paths) which ends up in kernel panics. >> >> Therefore just to be safe, I have reordered things a little (without changing the function): >> >> 1. check for resources (with some EPROBE_DEFER) >> 2. allocate non-devm (with optional EPROBE_DEFER) >> 3. allocate devm >> >> So this should be safe in any case. >> >> Please also compare a discussion >> >> https://lkml.org/lkml/2013/2/22/65 >> >>> >>>> Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> >>>> --- >>>> drivers/power/supply/twl4030_charger.c | 37 ++++++++++++++++++++-------------- >>>> 1 file changed, 22 insertions(+), 15 deletions(-) >>>> >>>> diff --git a/drivers/power/supply/twl4030_charger.c b/drivers/power/supply/twl4030_charger.c >>>> index 785a07bc4f39..945eabdbbc89 100644 >>>> --- a/drivers/power/supply/twl4030_charger.c >>>> +++ b/drivers/power/supply/twl4030_charger.c >>>> @@ -984,6 +984,28 @@ static int twl4030_bci_probe(struct platform_device *pdev) >>>> >>>> platform_set_drvdata(pdev, bci); >>>> >>>> + if (bci->dev->of_node) { >>>> + struct device_node *phynode; >>>> + >>>> + phynode = of_find_compatible_node(bci->dev->of_node->parent, >>>> + NULL, "ti,twl4030-usb"); >>>> + if (phynode) { >>>> + bci->transceiver = devm_usb_get_phy_by_node( >>>> + bci->dev, phynode, &bci->usb_nb); >>>> + if (IS_ERR(bci->transceiver) && >>>> + PTR_ERR(bci->transceiver) == -EPROBE_DEFER) >>>> + return -EPROBE_DEFER; /* PHY not ready */ >>>> + } >>>> + } >>>> + >>>> + bci->channel_vac = iio_channel_get(&pdev->dev, "vac"); >>>> + if (IS_ERR(bci->channel_vac)) { >>>> + if (PTR_ERR(bci->channel_vac) == -EPROBE_DEFER) >>>> + return -EPROBE_DEFER; /* iio not ready */ >>>> + dev_warn(&pdev->dev, "could not request vac iio channel"); >>>> + bci->channel_vac = NULL; >>>> + } >>>> + >>> >>> You should not request non-devm managed iio_channel before >>> devm-managed power-supply. >> >> Well, it is not *me* doing that. >> >> It is the unpatched driver which already does. See: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/power/supply/twl4030_charger.c?h=v4.12-rc4#n1069 >> >> I have just moved this line to a different location to be able to add a proper EPROBE_DEFER return path. >> >>> This could be fixed by switching to >>> devm_iio_channel_get(), which also cleans up some code. >> >> Yes, this could be an alternative solution. >> We still need EPROBE_DEFER handling. >> >>> >>> I suspect, that this is also your IRQ problem, since iio_channel >>> is currently free'd before irqs are free'd, but its used in irq >>> code. >> >> Hm. No. >> >> In upstream code it is never freed on probe failure because there is only >> an error return (goto fail) after allocating irqs in case the >> twl_i2c_write_u8 fails. Which usually doesn't. >> >> The EPROBE_DEFER returned by iio_channel_get not being ready simply prints >> a warning and turns off AC detection (bci->channel_vac = NULL) forever. >> >>> >>>> bci->ac = devm_power_supply_register(&pdev->dev, &twl4030_bci_ac_desc, >>>> NULL); >>>> if (IS_ERR(bci->ac)) { >>>> @@ -1017,25 +1039,10 @@ static int twl4030_bci_probe(struct platform_device *pdev) >>>> return ret; >>>> } >>>> >>>> - bci->channel_vac = iio_channel_get(&pdev->dev, "vac"); >>>> - if (IS_ERR(bci->channel_vac)) { >> >> My first attempt to fix EPROBE_DEFER was to add this >> >> + if (PTR_ERR(bci->channel_vac) == -EPROBE_DEFER) >> + return -EPROBE_DEFER; /* iio not ready */ >> >>>> - bci->channel_vac = NULL; >>>> - dev_warn(&pdev->dev, "could not request vac iio channel"); >>>> - } >>>> - >>>> INIT_WORK(&bci->work, twl4030_bci_usb_work); >>>> INIT_DELAYED_WORK(&bci->current_worker, twl4030_current_worker); >>>> >>>> bci->usb_nb.notifier_call = twl4030_bci_usb_ncb; >>>> - if (bci->dev->of_node) { >>>> - struct device_node *phynode; >>>> - >>>> - phynode = of_find_compatible_node(bci->dev->of_node->parent, >>>> - NULL, "ti,twl4030-usb"); >>>> - if (phynode) >>>> - bci->transceiver = devm_usb_get_phy_by_node( >>>> - bci->dev, phynode, &bci->usb_nb); >> >> and this >> >> + if (IS_ERR(bci->transceiver) && >> + PTR_ERR(bci->transceiver) == -EPROBE_DEFER) { >> + ret = -EPROBE_DEFER; /* PHY not ready */ >> + goto fail; >> >> This did run (and potentially return) after installing devm_request_threaded_irq leading >> to observation of severe kernel panics by interrupts. >> >> Moving the iio channel allocation before devm_request_threaded_irq made them go away. >> >>>> - } >>>> >>>> /* Enable interrupts now. */ >>>> reg = ~(u32)(TWL4030_ICHGLOW | TWL4030_ICHGEOC | TWL4030_TBATOR2 | >>> >>> -- Sebastian >> >> How important is it to keep the current sequence of devm_request_threaded_irq() + (devm_)iio_channel_get() untouched? >> >> The reason I ask is that it is more likely for (devm_)iio_channel_get() to fail than devm_request_threaded_irq(). >> >> Hence the iio channel should imho be always allocated first, so that we skip allocating+freeing unused irq handlers in case >> of iio not being ready. >> >> Therefore, I suggest to keep the proposed reordering even if we think devm-conversion of iio_channel_get() alone >> would solve it equally well. >> >> Next: should there be two separate patches? One for converting the non-devm iio_channel_get() and cleaning up error path. >> And one for adding EPROBE_DEFER error path. >> >> Or keep it in a single patch because they only make sense if done together (you can't add/remove deferred probing >> without converting and/or moving iio_channel_get())? >> >> So please advise how to proceed. >> > > You should request irq as late as possible in probe - it's safest way to go always. > You see crushes simply because request_irq enables IRQ and IRQ can trigger immediately, so > IRQ handler will run and all required resources should be ready and initialized. > > In this case: > twl4030_bci_interrupt() -> twl4030_charger_update_current() -> ac_available() -> iio_read_channel_processed() > OOOPS. > > So, first thing to do is to reorder probe to ensure that sequence is safe. That is exactly what I guessed when proposing the reordering patch. > Then other stuff - devm, EPROBE_DEFER ... IMHO, reordering alone doesn't make much sense as a single patch. Or does it? BR and thanks, Nikolaus -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
