Hi Tony, > On May 18, 2015, at 21:14 , Tony Lindgren <tony@xxxxxxxxxxx> wrote: > > * Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx> [150518 11:02]: >> Hi Tony, >> >>> On May 18, 2015, at 20:03 , Tony Lindgren <tony@xxxxxxxxxxx> wrote: >>> >>> * Robert Nelson <robertcnelson@xxxxxxxxx> [150518 09:51]: >>>> On Mon, May 18, 2015 at 11:29 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: >>>>> * Robert Nelson <robertcnelson@xxxxxxxxx> [150518 09:15]: >>>>>> On Mon, May 18, 2015 at 10:21 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: >>>>>> >>>>>> All the rev information is in the board's eeprom: >>>>>> >>>>>> hexdump -e '8/1 "%c"' /sys/bus/i2c/devices/0-0050/eeprom -s 12 -n 4 >>>>>> >>>>>> Rev A5B >>>>>> 0A5B >>>>>> >>>>>> Rev C >>>>>> 000C >>>>>> >>>>>> Just another default qwerk to add to Pantelis' bone_capemgr. ;) >>>>> >>>>> It seems we should not even instantiate some devices on BBB >>>>> until the EEPROM is parsed.. So maybe something like this: >>>>> >>>>> 1. The problem devices are initially set with status = "disabled" >>>>> in the dts >>>>> >>>>> 2. We set up drivers/*/bbb-eeprom.c that parses the board >>>>> revision at module_init time, and then flips the selected >>>>> devices to have status = "enabled" and populates the revision >>>>> info based on the eeprom and SoC revision passed in pdata. >>>>> Then those devices get their struct device created and >>>>> probed, but at a much later time. >>>>> >>>>> So rather than trying to init all that early, let's just >>>>> init them much later when we have the proper I2C driver >>>>> running? >>>> >>>> I see that working just fine. We (beagleboard.org) enforce the eeprom >>>> data, as all the official images require a proper baseboard eeprom. >>> >>> OK >>> >>>> We just have to be very careful to limit the scope, otherwise we will >>>> end up with Pantelis' rejected capebus from the v3.2.x days... >>> >>> Naturally I was thinking #2 above would use Pantelis' code for >>> CONFIG_OF_OVERLAY in mainline. But instead of the earlier patches, >>> we can make things happen much later on to avoid the detect of >>> EEPROM early on. >> >> Already been taken care of: >> >> https://lkml.org/lkml/2015/2/18/258 >> >> The patchset works, but it still needs some review eyeballs. >> There might be a rename to variants or something. >> >> You were part of that thread too :) > > Right, and what I mean with #2 above is that we can make this all > into a regular drivers/* device driver with no need for the > early hacks in your series in arch/arm/mach-omap2/am33xx-dt-quirks.c. > It’s going to be tough. This is touching the pmic that needs to be initialized early since a whole bunch of drivers depend on it. >> I think it’s best if we go this path instead of twiddling with the >> status properties manually. Conceptually the idea is similar to >> the detection of the white/black, with the added joy of revision >> detection. > > If some device drivers depend on the I2C EEPROM, we should not > create the struct device entry for those until the I2C EEPROM > driver has parsed the EEPROM. And there's no need to do that > early, we want to do everything as late as possible. That way > we have real debug console available in most cases. > FWIW the first patch used an early platform device, but that made things even more complicated. >> Ain’t hardware designers a fun bunch or what? > > We need something equal to the MS DOS boot floppy to limit their > ideas :) > I think hardware people still clink to the idea that this whole OS business is a fad and MSDOS will make a comeback any minute now :) > Regards, > > Tony Regards — Pantelis -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
