On Thu, 21 Jun 2012 12:04:26 +0530 "DebBarma, Tarun Kanti"
<tarun.kanti@xxxxxx> wrote:
> On Thu, Jun 21, 2012 at 8:46 AM, NeilBrown <neilb@xxxxxxx> wrote:
> > On Thu, 14 Jun 2012 23:24:10 +0530 "DebBarma, Tarun Kanti"
> > <tarun.kanti@xxxxxx> wrote:
> >
> >> On Thu, Jun 14, 2012 at 5:45 AM, NeilBrown <neilb@xxxxxxx> wrote:
> >> > On Fri, 11 May 2012 17:30:48 -0700 Kevin Hilman <khilman@xxxxxx> wrote:
> >> >
> >> >> Hi Grant,
> >> >>
> >> >> Here's the final round of GPIO cleanups for v3.5. This branch is based
> >> >> on my for_3.5/fixes/gpio branch you just pulled.
> >> >>
> >> >> Kevin
> >> >
> >> > Hi.
> >> >
> >> > I'm not sure if it was this series or the following cleanups which broke
> >> > things for me, but I've been trying 3.5-rc2 on my GTA04 and the serial
> >> > console (ttyO2) dies as soon as the omap-gpio driver initialises.
> >> >
> >> > After some digging I came up with this patch to gpio-omap.c
> >> >
> >> > @@ -1124,6 +1124,9 @@ static int __devinit omap_gpio_probe(struct platform_device *pdev)
> >> >
> >> > platform_set_drvdata(pdev, bank);
> >> >
> >> > + if (bank->get_context_loss_count)
> >> > + bank->context_loss_count =
> >> > + bank->get_context_loss_count(bank->dev);
> >> > pm_runtime_enable(bank->dev);
> >> > pm_runtime_irq_safe(bank->dev);
> >> > pm_runtime_get_sync(bank->dev);
> >> >
> >> > which fixes it.
> >> >
> >> > What was happening was that when omap_gpio_probe calls pm_runtime_get_sync,
> >> > it calls
> >> > _od_runtime_resume -> pm_generic_runtime_resume -> omap_gpio_runtime_resume
> >> > -> omap_gpio_restore_context
> >> >
> >> > and then the serial port stops.
> >> > I reasoned that the context probably hadn't been set up yet, so restoring
> >> > from it broke things.
> >> > Initialising bank->context_loss_count seems sensible and would ensure that
> >> > we didn't try to restore the context until it has actually been lost.
> >>
> >> I thought the following code exactly does that. That is context_lost_cnt_after
> >> would be zero until there is context loss. The bank->context_loss_count is zero
> >> at the beginning. So, (context_lost_cnt_after != bank->context_loss_count) would
> >> be false and hence context restore should NOT happen? Not sure if I am
> >> over looking
> >> anything here....
> >>
> >> omap_gpio_runtime_resume(...)
> >> {
> >> ...
> >> if (bank->get_context_loss_count) {
> >> context_lost_cnt_after =
> >> bank->get_context_loss_count(bank->dev);
> >> if (context_lost_cnt_after != bank->context_loss_count) {
> >> omap_gpio_restore_context(bank);
> >> } else {
> >> spin_unlock_irqrestore(&bank->lock, flags);
> >> return 0;
> >> }
> >> }
> >> ...
> >> }
> >
> > Hi,
> > I've looked more closely at this now.
> >
> > The problem is that the initial context loss count is *not* zero. Not always.
> > The context loss count is the sum of
> >
> > count = pwrdm->state_counter[PWRDM_POWER_OFF];
> > count += pwrdm->ret_logic_off_counter;
> >
> > for (i = 0; i < pwrdm->banks; i++)
> > count += pwrdm->ret_mem_off_counter[i];
> >
> > (from pwrdm_get_context_loss_count()).
> >
> > These are initlialised in _pwrdm_register
> >
> > /* Initialize the powerdomain's state counter */
> > for (i = 0; i < PWRDM_MAX_PWRSTS; i++)
> > pwrdm->state_counter[i] = 0;
> >
> > pwrdm->ret_logic_off_counter = 0;
> > for (i = 0; i < pwrdm->banks; i++)
> > pwrdm->ret_mem_off_counter[i] = 0;
> >
> > pwrdm_wait_transition(pwrdm);
> > pwrdm->state = pwrdm_read_pwrst(pwrdm);
> > pwrdm->state_counter[pwrdm->state] = 1;
> >
> >
> > What I'm seeing is that for wkup_pwrdm and dpll{3,4,5}_pwrdm,
> > the state that pwrdm_read_pwrst returns is PWRDM_POWER_OFF.
> > So that state_counter gets initialised to '1', and so the initial
> > context_loss_count, which includes that counter, is also '1'.
> > I think it is the wkup_pwrdm that covers the GPIOs that are causing problems
> > for me.
> I just put a log in omap_gpio_probe() to see the value of context_loss_count.
> GPIO Bank 0 (WKUP Domain) always shows the count as '1'.
>
> [ 0.169494] omap_gpio omap_gpio.0: context_loss_count=1
> [ 0.170227] gpiochip_add: registered GPIOs 0 to 31 on device: gpio
> [ 0.170471] OMAP GPIO hardware version 0.1
> [ 0.170623] omap_gpio omap_gpio.1: context_loss_count=0
> [ 0.170928] gpiochip_add: registered GPIOs 32 to 63 on device: gpio
> [ 0.171295] omap_gpio omap_gpio.2: context_loss_count=0
> [ 0.171600] gpiochip_add: registered GPIOs 64 to 95 on device: gpio
> [ 0.171936] omap_gpio omap_gpio.3: context_loss_count=0
> [ 0.172241] gpiochip_add: registered GPIOs 96 to 127 on device: gpio
> [ 0.172576] omap_gpio omap_gpio.4: context_loss_count=0
> [ 0.172882] gpiochip_add: registered GPIOs 128 to 159 on device: gpio
> [ 0.173217] omap_gpio omap_gpio.5: context_loss_count=0
> [ 0.173522] gpiochip_add: registered GPIOs 160 to 191 on device: gpio
That's consistent with what I see, and confirm that initialising the
context_lost_count to zero isn't always correct.
Thanks,
NeilBrown
> --
> Tarun
> >
> > So either there is something seriously wrong with pwrdm_read_pwrst and it
> > shouldn't be reporting that the wkup_pwrdm is off, or we need to initialise
> > bank->context_loss_count like my patch does.
> >
> > NeilBrown
> --
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