On Tue, 4 Mar 2025 12:18:10 -0600
Chris Morgan <macroalpha82@xxxxxxxxx> wrote:
> On Tue, Dec 17, 2024 at 02:04:37AM +0800, Chen-Yu Tsai wrote:
> > On Tue, Dec 17, 2024 at 2:01 AM Chris Morgan <macroalpha82@xxxxxxxxx> wrote:
> > >
> > > On Wed, Dec 11, 2024 at 09:58:26PM +0000, Jonathan Cameron wrote:
> > > > On Tue, 10 Dec 2024 16:48:57 -0600
> > > > Chris Morgan <macroalpha82@xxxxxxxxx> wrote:
> > > >
> > > > > From: Chris Morgan <macromorgan@xxxxxxxxxxx>
> > > > >
> > > > > After performing a git bisect, I identified a commit that broke the
> > > > > battery and charger driver for my AXP717 PMIC. This was caused by
> > > > > commit e37ec3218870 ("mfd: axp20x: Allow multiple regulators").
> > > > >
> > > > > After digging into it, it appears when mfd_add_devices was called with
> > > > > a platform ID of PLATFORM_DEVID_NONE, the devm_iio_channel_get() call
> > > > > made by the various AXP20X power drivers would not be able to generate
> > > > > a dev_name(dev) for some reason, and the iio_channel_get() call used in
> > > > > the devm_ helper would fall back to making a iio_channel_get_sys()
> > > > > call. After the platform ID was updated, now iio_channel_get() is no
> > > > > longer falling back to iio_channel_get_sys(). At least this is my
> > > > > limited understanding of what happened.
> > > >
> > > > The dev_name(dev) not getting a name doesn't sound quite right to me.
> > > >
> > > > Time to look at the ancient creaking ghost that is the iio_map handling.
> > > >
> > > > struct iio_channel *iio_channel_get(struct device *dev,
> > > > const char *channel_name)
> > > > {
> > > > const char *name = dev ? dev_name(dev) : NULL;
> > > > struct iio_channel *channel;
> > > >
> > > > if (dev) {
> > > > channel = fwnode_iio_channel_get_by_name(dev_fwnode(dev),
> > > > channel_name);
> > > > if (!IS_ERR(channel) || PTR_ERR(channel) != -ENODEV)
> > > > return channel;
> > > > }
> > > >
> > > > return iio_channel_get_sys(name, channel_name);
> > > > }
> > > > EXPORT_SYMBOL_GPL(iio_channel_get);
> > > >
> > > > We didn't invent the relevant phandle stuff in DT via the patch you point at
> > > > so all that matters is what gets passed to that iio_channel_get_sys()
> > > >
> > > > So key here is that dev should be set, so we are passing dev_name(dev) into
> > > > iio_channel_get_sys()
> > > > I'm guessing that changed...
> > > >
> > > > Ah. The iio_maps in
> > > > https://elixir.bootlin.com/linux/v6.12.4/source/drivers/iio/adc/axp20x_adc.c#L158
> > > > are our problem. Those hardcode the consumer_dev name. The fix just changed
> > > > those names. Back when this infrastructure was written we were in the world of
> > > > board files, so everything was hard coded in them - or in an MFD like this
> > > > it was treated as a singleton device.
> > > >
> > > > So as to how to fix it... Assuming the new device names are the same for all
> > > > the mfd parts that make up each pmic, then you should be able to figure out the
> > > > extra the number and build the channel maps to allow you to find the numbered
> > > > devices.
> > >
> > > Is there a way to figure out the device number at runtime? The issue is
> > > each time the device attempts to probe and fails, the device number
> > > increments, making it a "hitting a moving target" problem.
> >
> > The ADC device is a mfd cell or child device of the PMIC mfd device.
> > So you should be able to use dev->parent to get it directly? We do
> > that at least for the regulator driver.
>
> Sorry to dig up such an old thread. I'm taking a look at this one again
> and can confirm passing pdev->dev.parent to devm_iio_channel_get() is
> insufficient to get the driver to find the correct ADC channel. Would
> there be another/better way to do this other than the
> devm_iio_channel_get_sys() as proposed? Or should we be walking the
> parent somehow looking for the named ADC channel on each child device
> (which would also require a new symbol most likely)?
Hi Chris
