Re: [PATCH] gpio/omap: fix wakeups on level-triggered GPIOs

[Grant Likely <grant.likely@secretlab.ca>]

On Mon,  5 Mar 2012 15:10:04 -0800, Kevin Hilman <khilman@ti.com> wrote:
> While both level- and edge-triggered GPIOs are capable of generating
> interrupts, only edge-triggered GPIOs are capable of generating a
> module-level wakeup to the PRCM (c.f. 34xx NDA TRM section 25.5.3.2.)
> 
> In order to ensure that devices using level-triggered GPIOs as
> interrupts can also cause wakeups (e.g. from idle), this patch enables
> edge-triggering for wakeup-enabled, level-triggered GPIOs when a GPIO
> bank is runtime-suspended (which also happens during idle.)
> 
> This fixes a problem found in GPMC-connected network cards with GPIO
> interrupts (e.g. smsc911x on Zoom3, Overo, ...) where network booting
> with NFSroot was very slow since the GPIO IRQs used by the NIC were
> not generating PRCM wakeups, and thus not waking the system from idle.
> NOTE: until v3.3, this boot-time problem was somewhat masked because
> the UART init prevented WFI during boot until the full serial driver
> was available.  Preventing WFI allowed regular GPIO interrupts to fire
> and this problem was not seen.  After the UART runtime PM cleanups, we
> no longer avoid WFI during boot, so GPIO IRQs that were not causing
> wakeups resulted in very slow IRQ response times.
> 
> Tested on platforms using level-triggered GPIOs for network IRQs using
> the SMSC911x NIC: 3530/Overo and 3630/Zoom3.
> 
> Reported-by: Tony Lindgren <tony@atomide.com>
> Tested-by: Tarun Kanti DebBarma <tarun.kanti@ti.com>
> Tested-by: Tony Lindgren <tony@atomide.com>
> Signed-off-by: Kevin Hilman <khilman@ti.com>

Applied, thx.

g.

> ---
> Grant, here's another one for your gpio/next branch, and applies on
> top of the for_3.4/gpio/runtime-pm-cleanup branch you've already
> pulled from me.  While it's a fix, it's not a regressions since
> this problem has been around for awhile, so it can be for 3.4.
> 
>  drivers/gpio/gpio-omap.c |   34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index f49bd6f..752ae9b 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -1196,8 +1196,30 @@ static int omap_gpio_runtime_suspend(struct device *dev)
>  	struct gpio_bank *bank = platform_get_drvdata(pdev);
>  	u32 l1 = 0, l2 = 0;
>  	unsigned long flags;
> +	u32 wake_low, wake_hi;
>  
>  	spin_lock_irqsave(&bank->lock, flags);
> +
> +	/*
> +	 * Only edges can generate a wakeup event to the PRCM.
> +	 *
> +	 * Therefore, ensure any wake-up capable GPIOs have
> +	 * edge-detection enabled before going idle to ensure a wakeup
> +	 * to the PRCM is generated on a GPIO transition. (c.f. 34xx
> +	 * NDA TRM 25.5.3.1)
> +	 *
> +	 * The normal values will be restored upon ->runtime_resume()
> +	 * by writing back the values saved in bank->context.
> +	 */
> +	wake_low = bank->context.leveldetect0 & bank->context.wake_en;
> +	if (wake_low)
> +		__raw_writel(wake_low | bank->context.fallingdetect,
> +			     bank->base + bank->regs->fallingdetect);
> +	wake_hi = bank->context.leveldetect1 & bank->context.wake_en;
> +	if (wake_hi)
> +		__raw_writel(wake_hi | bank->context.risingdetect,
> +			     bank->base + bank->regs->risingdetect);
> +
>  	if (bank->power_mode != OFF_MODE) {
>  		bank->power_mode = 0;
>  		goto update_gpio_context_count;
> @@ -1246,6 +1268,18 @@ static int omap_gpio_runtime_resume(struct device *dev)
>  
>  	spin_lock_irqsave(&bank->lock, flags);
>  	_gpio_dbck_enable(bank);
> +
> +	/*
> +	 * In ->runtime_suspend(), level-triggered, wakeup-enabled
> +	 * GPIOs were set to edge trigger also in order to be able to
> +	 * generate a PRCM wakeup.  Here we restore the
> +	 * pre-runtime_suspend() values for edge triggering.
> +	 */
> +	__raw_writel(bank->context.fallingdetect,
> +		     bank->base + bank->regs->fallingdetect);
> +	__raw_writel(bank->context.risingdetect,
> +		     bank->base + bank->regs->risingdetect);
> +
>  	if (!bank->enabled_non_wakeup_gpios || !bank->workaround_enabled) {
>  		spin_unlock_irqrestore(&bank->lock, flags);
>  		return 0;
> -- 
> 1.7.9.2
> 

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies,Ltd.