Re: [PATCH] usb: phy: add dedicated notifier for charger events

[Ivaylo Dimitrov]

ping

On 16.11.22 г. 9:11 ч., Ivaylo Dimitrov wrote:
> On 14.11.22 г. 18:46 ч., Ivaylo Dimitrov wrote:
> > Hi,
> >
> > On 14.11.22 г. 18:14 ч., Greg KH wrote:
> > > On Mon, Nov 14, 2022 at 02:56:02PM +0200, Ivaylo Dimitrov wrote:
> > > > usb_phy::notifier is already used by various PHY drivers (including
> > > > phy_generic) to report VBUS status changes and its usage conflicts with
> > > > charger current limit changes reporting.
> > >
> > > How exactly does it conflict?
> >
> > see below
> >
> > > > Fix that by introducing a second notifier that is dedicated to usb 
> > > > charger
> > > > notifications. Add usb_charger_XXX_notifier functions. Fix charger 
> > > > drivers
> > > > that currently (ab)use usb_XXX_notifier() to use the new API.
> > >
> > > Why not just set the notifier type to be a new one instead of adding a
> > > whole new notifier list?  Or use a real callback?  notifier lists are
> > > really horrid and should be avoided whenever possible.
> >
> > Not sure what you mean by "notifier type', but if that is that val 
> > parameter of atomic_notifier_call_chain(), the way it is used by usb 
> > charger FW:
> >
> > https://elixir.bootlin.com/linux/latest/source/drivers/usb/phy/phy.c#L132
> >
> > is not compatible with:
> >
> > https://elixir.bootlin.com/linux/latest/source/drivers/usb/phy/phy-generic.c#L185 
> >
> >
> > for example, IIUC.
> >
> > The former wants to send max current as val, while latter sends event 
> > type as val. Sure, I may create some kind of hack, like using the MSB 
> > to denote charger events, but that doesn't feel right.
> >
> > Or, shall I do something else and fix the usage all over the place? 
> > Please elaborate.
>
> Digging further into that, it seems phy-ab8500-usb.c is also using 
> usb_phy::notifier in non-standard way, it sends events from 
> ux500_musb_vbus_id_status instead of usb_phy_events. I don't know the 
> history behind, but right now we have at least 3 incompatible usages of 
> usb_phy::notifier:
>
> 1. Most of the phy and charger drivers use usb_phy_events as notifier type
>
> 2. phy-ab8500-usb.c uses ux500_musb_vbus_id_status as notifier type, I 
> am not the only one to hit that it seems 
> https://elixir.bootlin.com/linux/v6.1-rc5/source/drivers/power/supply/ab8500_charger.c#L3191 
>
>
> 3. USB charger framework uses max charging current as notifier type.
>
> Moreover, a charger driver in a system that has gadget drivers support 
> and phy that has extcon charger cable detection support and registers to 
> phy notifier, will inevitably receive (1) and (3) types of 
> notifications, without any way to distinguish I was able to find.
>
> I don't really see how those can be merged to use one notifier only, 
> without fixing most of USB phy and gadget drivers and half of charger 
> drivers. Not that I like adding the second notifier, I just don;t see 
> other way.
>
> Regards,
> Ivo
>
> > In regards to callback - I didn't want to come-up with a whole new 
> > API, but just fix the current one. Also, a single callback will not be 
> > enough - imagine a case with 2 batteries that have to be charged by a 
> > single USB port, so 2 separate charger devices, most-probably. We will 
> > have to keep a list of callback functions somehow. I admit my lack of 
> > knowledge, but, do we already have such API to use?
> >
> > > > Fixes: a9081a008f84 ("usb: phy: Add USB charger support")
> > > >
> > > > Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@xxxxxxxxx>
> > >
> > > You can't have a blank line between there, checkpatch.pl should have
> > > complained.
> >
> > it didn't:
> >
> > ./scripts/checkpatch.pl 
> > 0001-usb-phy-add-dedicated-notifier-for-charger-events.patch
> > total: 0 errors, 0 warnings, 90 lines checked
> >
> > 0001-usb-phy-add-dedicated-notifier-for-charger-events.patch has no 
> > obvious style problems and is ready for submission.
> >
> > Will fix, if I am to send v2
> >
> > Thanks,
> > Ivo
> >
> > > thanks,
> > >
> > > greg k-h