Hi Dan, On Mon, Jul 12, 2021 at 09:13:00AM +0100, Daniel Scally wrote: > On 11/07/2021 17:55, Laurent Pinchart wrote: > > On Sat, Jul 10, 2021 at 11:54:26PM +0100, Daniel Scally wrote: > >> On 10/07/2021 23:28, Laurent Pinchart wrote: > >>> On Thu, Jul 08, 2021 at 11:42:24PM +0100, Daniel Scally wrote: > >>>> Hello all > >>>> > >>>> See previous series for some background context [1] > >>>> > >>>> Some x86 laptops with ACPI tables designed for Windows have a TPS68470 > >>>> PMIC providing regulators and clocks to camera modules. The DSDT tables for > >>>> those cameras lack any power control methods, declaring only a > >>>> dependency on the ACPI device representing the TPS68470. This leaves the > >>>> regulator framework with no means of determining appropriate voltages for the > >>>> regulators provided by the PMIC, or of determining which regulators relate to > >>>> which of the sensor's requested supplies. > >>>> > >>>> This series is a prototype of an emulation of the device tree regulator > >>>> initialisation and lookup functions, using software nodes. Software nodes > >>>> relating to each regulator are registered as children of the TPS68470's ACPI > >>>> firmware node. Those regulators have properties describing their constraints > >>>> (for example "regulator-min-microvolt"). Similarly, software nodes are > >>>> registered and assigned as secondary to the Camera's firmware node - these > >>>> software nodes have reference properties named after the supply in the same > >>>> way as device tree's phandles, for example "avdd-supply", and linking to the > >>>> software node assigned to the appropriate regulator. We can then use those > >>>> constraints to specify the appropriate voltages and the references to allow the > >>>> camera drivers to look up the correct regulator device. > >>>> > >>>> Although not included in this series, I would plan to use a similar method for > >>>> linking the clocks provided by the TPS68470 to the sensor so that it can be > >>>> discovered too. > >>>> > >>>> I'm posting this to see if people agree it's a good approach for tackling the > >>>> problem; I may be overthinking this and there's a much easier way that I should > >>>> be looking at instead. It will have knock-ons in the cio2-bridge code [2], as > >>>> that is adding software nodes to the same sensors to connect them to the media > >>>> graph. Similarly, is the board file an acceptable solution, or should we just > >>>> define the configuration for these devices (there's three orf our laptop models > >>>> in scope) in int3472-tps68470 instead? > >>> > >>> I may have missed something, but if you load the SGo2 board file, won't > >>> it create the regulator software nodes if it finds an INT3472, > >>> regardless of whether the device is an SGo2 ? If you happen to do so on > >>> a machine that requires different voltages, that sounds dangerous. > >> > >> Ah, yes - hadn't thought of that. If a driver registered regulators with > >> those names, it would try to apply those voltages during registration. > >> Good point. > >> > >>> Given that INT3472 models the virtual "Intel Skylake and Kabylake camera > >>> PMIC", I think moving device-specific information to the int3472 driver > >>> may make sense. I'm unsure what option is best though, having all the > >>> data (regulators, clocks, but also data currently stored in the > >>> cio2-bridge driver) in a single file (or a single file per machine) is > >>> tempting. > >> > >> It is tempting, particularly because (assuming we do end up using this > >> approach) setting the references to the supplies in a board file like > >> this complicated the cio2-bridge code quite a bit, since it then needs > >> to extend the properties array against an already-existing software node > >> rather than registering a new one. But then, I don't particularly want > >> to handle that aspect of the problem in two separate places. > > > > If technically feasible, gathering all the data in a single place would > > be my preference. Whether that should take the form of software nodes in > > all cases, or be modelled as custom data that the int3472 driver would > > interpret to create the regulators and clocks is a different (but > > related) question. > > I'll have to think on that one then; the problem there is that the > cio2-bridge is just given ACPI HIDs for the sensors as "ok to parse > this", and of course the INT347A that is being dealt with here should > already be supported on most Surface platforms via the intel-skl-int3472 > stuff, so once the ov8865 edits are (posted and) accepted and that > driver is supported my plan would be to add it into the bridge. So we'd > need a way to exclude Go2 from that if we wanted to define all the > software nodes parts in a single board file instead. > > > The very important part is to ensure that the correct board data will be > > used, as otherwise we could damage the hardware. > > Not sure how this is usually guarded against; we could do a DMI match at > the start of the init function to confirm it's running on a Go2 and exit > if not? Unless the information is available in ACPI properties that the CIO2 bridge driver can access (and I wouldn't be surprised if it was the case in some way, there's are different IDs that we're not sure how to use, the Windows driver may very well map them to a set of reference designs), then a DMI match is likely the best option. > >>>> [1] https://lore.kernel.org/lkml/20210603224007.120560-1-djrscally@xxxxxxxxx/ > >>>> [2] https://elixir.bootlin.com/linux/latest/source/drivers/media/pci/intel/ipu3/cio2-bridge.c#L166 > >>>> > >>>> > >>>> Daniel Scally (2): > >>>> regulator: Add support for software node connections > >>>> platform/surface: Add Surface Go 2 board file > >>>> > >>>> MAINTAINERS | 6 + > >>>> drivers/platform/surface/Kconfig | 10 ++ > >>>> drivers/platform/surface/Makefile | 1 + > >>>> drivers/platform/surface/surface_go_2.c | 135 +++++++++++++++++++++ > >>>> drivers/regulator/Kconfig | 6 + > >>>> drivers/regulator/Makefile | 1 + > >>>> drivers/regulator/core.c | 23 ++++ > >>>> drivers/regulator/swnode_regulator.c | 111 +++++++++++++++++ > >>>> include/linux/regulator/swnode_regulator.h | 33 +++++ > >>>> 9 files changed, 326 insertions(+) > >>>> create mode 100644 drivers/platform/surface/surface_go_2.c > >>>> create mode 100644 drivers/regulator/swnode_regulator.c > >>>> create mode 100644 include/linux/regulator/swnode_regulator.h -- Regards, Laurent Pinchart
