On Tue, Apr 3, 2018 at 9:47 AM, Andrew Lunn <andrew@xxxxxxx> wrote: > On Tue, Apr 03, 2018 at 08:48:27AM -0700, Tim Harvey wrote: >> On Wed, Mar 28, 2018 at 8:14 AM, Tim Harvey <tharvey@xxxxxxxxxxxxx> wrote: >> > The Gateworks System Controller (GSC) is an I2C slave controller >> > implemented with an MSP430 micro-controller whose firmware embeds the >> > following features: >> > - I/O expander (16 GPIO's) using PCA955x protocol >> > - Real Time Clock using DS1672 protocol >> > - User EEPROM using AT24 protocol >> > - HWMON using custom protocol >> > - Interrupt controller with tamper detect, user pushbotton >> > - Watchdog controller capable of full board power-cycle >> > - Power Control capable of full board power-cycle >> > >> > see http://trac.gateworks.com/wiki/gsc for more details >> > >> <snip> >> > + >> > +/* >> > + * gsc_powerdown - API to use GSC to power down board for a specific time >> > + * >> > + * secs - number of seconds to remain powered off >> > + */ >> > +static int gsc_powerdown(struct gsc_dev *gsc, unsigned long secs) >> > +{ >> > + int ret; >> > + unsigned char regs[4]; >> > + >> > + dev_info(&gsc->i2c->dev, "GSC powerdown for %ld seconds\n", >> > + secs); >> > + regs[0] = secs & 0xff; >> > + regs[1] = (secs >> 8) & 0xff; >> > + regs[2] = (secs >> 16) & 0xff; >> > + regs[3] = (secs >> 24) & 0xff; >> > + ret = regmap_bulk_write(gsc->regmap, GSC_TIME_ADD, regs, 4); >> > + >> > + return ret; >> > +} >> >> Any feedback on the 'powerdown' sysfs attribute that hooks to this >> function? This allows the GSC to disable the board primary power >> supply for 2^32 seconds and is often used to 'reset' the board >> although it could also be used to put the board in a power down state >> longer. I'm wondering if there is a more appropriate API for this in >> the kernel that I don't know about. > > Hi Tim > > RTC can cause wakeup when an alarm is set. It looks like the DS1672 > does not have this. But you are emulating the DS1672 right? You could > add a second emulated RTC which does support an alarm? DS3232? Andrew, Thanks for the response! An RTC alarm may indeed be a good route for the overall sleep functionality I will look into that. What about the 'reset' functionality? Is there something in the power supply API for hooking in a GPIO based power switch (in my case it would be i2c) as I would think that would be common for ATX supplies? I didn't see anything in Documentation/power. This is what led me to the restart handler idea. Ultimately when someone issues a 'reboot' I would like it to use the GSC to power-cycle the board. > >> I would also like to register a restart handler using this but I >> believe that ARM restart handlers currently can not use I2C - is that >> correct? > > There are plenty which use GPIOs, or UARTs. Not seen any which use > i2c. What do you think does not work at this point? I'll have to dig around for the e-mail thread. I recall someone else trying to implement a restart handler for something hanging off i2c and the issue was that by the time the (ARM) restart handler got called interrupts were disabled making i2c unreliable. I have hooked the ARM restart handler to my GSC powerdown in some kernels and have had mixed results. When the handler gets called from a clean 'reboot' things seem fine but if its called from some error condition that halts the kernel it seems that i2c may not be reliable anymore. Regards, Tim -- 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
