On 07/02/2012 10:37 AM, Kevin Hilman wrote:
"DebBarma, Tarun Kanti" <tarun.kanti@xxxxxx> writes:
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.
I think the original patch from Neil looks right.
Note that we would need something like this in the case where we built
the GPIO driver as a module and it was unloaded/reloaded where the
starting point of the context-loss count would not be zero.
Neil, care to send a patch w/changelog?
Nevermind, this same issue has come up in another thread with a patch
proposed.
Kevin
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