On Mon, 25 May 2020, Michael Walle wrote: > Am 2020-05-15 12:28, schrieb Lee Jones: > > On Thu, 30 Apr 2020, Michael Walle wrote: > > > > > Hi Lee, > > > > > > Am 2020-04-23 19:45, schrieb Michael Walle: > > > > There might be multiple children with the device tree compatible, for > > > > example if a MFD has multiple instances of the same function. In this > > > > case only the first is matched and the other children get a wrong > > > > of_node reference. > > > > Add a new option to match also against the unit address of the child > > > > node. Additonally, a new helper OF_MFD_CELL_REG is added. > > > > > > > > > Do you think this is feasible? I guess this is the biggest uncertainty > > > for me at the moment in this patch series. > > > > I think it sounds fine in principle. So long as it doesn't change the > > existing behaviour when of_reg isn't set. > > > > > > Signed-off-by: Michael Walle <michael@xxxxxxxx> > > > > --- > > > > drivers/mfd/mfd-core.c | 29 ++++++++++++++++++++--------- > > > > include/linux/mfd/core.h | 26 ++++++++++++++++++++------ > > > > 2 files changed, 40 insertions(+), 15 deletions(-) [...] > > > > diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h > > > > index d01d1299e49d..c2c0ad6b14f3 100644 > > > > --- a/include/linux/mfd/core.h > > > > +++ b/include/linux/mfd/core.h > > > > @@ -13,8 +13,11 @@ > > > > #include <linux/platform_device.h> > > > > > > > > #define MFD_RES_SIZE(arr) (sizeof(arr) / sizeof(struct resource)) > > > > +#define MFD_OF_REG_VALID BIT(31) > > > > What about 64bit platforms? > > The idea was to have this as a logical number. I.e. for now you may only > have one subdevice per unique compatible string. In fact, if you have a > look at the ab8500.c, there are multiple "stericsson,ab8500-pwm" > subdevices. But there is only one DT node for all three of it. I guess > this works as long as you don't use phandles to reference the pwm node > in the device tree. Or you don't want to use device tree properties > per subdevice (for example the "timeout-sec" of a watchdog device). > > So to circumvent this, I thought of having the unit-address (and thus > the "reg" property) to differentiate between multiple subdevices. Now > there is one special case for me: this board management controller > might be upgradable and it might change internally. Thus I came up > with that logical numbering of subdevices. Rob doesn't seem to be a > fan of that, though. Therefore, having bit 31 as a valid indicator > leaves you with 2^31 logical devices, which should be enough ;) > > Rob proposed to have the internal offset as the unit-address. But > in that case I can also use devm_of_platform_populate() and don't > need the OF_MFD_CELL_REG; I'd just parse the reg offset in each > individual subdevice driver. But like I said, I wanted to keep the > internal offsets out of the device tree. Oh, I see what you're doing. So you're adding an arbitrary ID to the device's reg property in DT? How is this not a hack? Why don't you use the full address for identification? -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
