On Mon, Jun 25, 2012 at 11:48 AM, NeilBrown <neilb@xxxxxxx> wrote:
> 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.
I am just wondering if the context_lost_count = 1 for GPIO in WKUP domain
is expected. In that case we have to add additional logic in runtime callbacks
to skip context restore/save for WKUP domain GPIOs.
But let's hear what Kevin says.
--
Tarun
>
> 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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