On 06/09/2017 01:05 AM, H. Nikolaus Schaller wrote: > Hi, > >> Am 07.06.2017 um 22:44 schrieb Sebastian Reichel <s...@kernel.org>: >> >> 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 <h...@goldelico.com> >>> --- >>> 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. Then other stuff - devm, EPROBE_DEFER ... -- regards, -grygorii
