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
--
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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