On 06/09/2017 11:59 PM, H. Nikolaus Schaller wrote: > 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? > The question is - is there bug in driver or not? As per current code seems yes. You can easily test it by directly calling twl4030_charger_interrupt() right after IRQ is requested. there is a bug if it will crush. As for me it more reasonable to move forward using smaller steps. Thanks for you work and patches. -- regards, -grygorii -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
