Re: [PATCH] gpio: omap-gpio: add support for pm_runtime autosuspend

[Felipe Balbi <balbi@ti.com>]

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Hi,

On Fri, Oct 26, 2012 at 09:55:30AM +0200, Tim Niemeyer wrote:
> Adds support for configuring the omap-gpio driver use autosuspend for
> runtime power management. This can reduce the latency in using it by
> not suspending the device immediately on idle. If another access takes
> place before the autosuspend timeout (2 secs), the call to resume the
> device can return immediately saving some save/ restore cycles.
> 
> I use a gpio to monitor a spi transfer which occurs every 250µs. The
> suspend overhead is to high, so almost every second transfer is lost.
> This patch fixes that.
> 
> Signed-off-by: Tim Niemeyer <tim.niemeyer@corscience.de>
> ---
>  drivers/gpio/gpio-omap.c |   23 ++++++++++++++++++-----
>  1 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index 94cbc84..92f48cb 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -31,6 +31,7 @@
>  #include <asm/mach/irq.h>
>  
>  #define OFF_MODE	1
> +#define GPIO_AUTOSUSPEND_TIMEOUT                2000
>  
>  static LIST_HEAD(omap_gpio_list);
>  
> @@ -628,8 +629,10 @@ static void omap_gpio_free(struct gpio_chip *chip, unsigned offset)
>  	 * If this is the last gpio to be freed in the bank,
>  	 * disable the bank module.
>  	 */
> -	if (!bank->mod_usage)
> -		pm_runtime_put(bank->dev);
> +	if (!bank->mod_usage) {

while at that I would drop this bank->mod_usage nonsense and let
power core handle reference counting.

> +		pm_runtime_mark_last_busy(bank->dev);
> +		pm_runtime_put_autosuspend(bank->dev);
> +	}
>  }
>  
>  /*
> @@ -715,7 +718,8 @@ static void gpio_irq_handler(unsigned int irq, struct irq_desc *desc)
>  exit:
>  	if (!unmasked)
>  		chained_irq_exit(chip, desc);
> -	pm_runtime_put(bank->dev);
> +	pm_runtime_mark_last_busy(bank->dev);
> +	pm_runtime_put_autosuspend(bank->dev);
>  }
>  
>  static void gpio_irq_shutdown(struct irq_data *d)
> @@ -1132,6 +1136,8 @@ static int __devinit omap_gpio_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, bank);
>  
> +	pm_runtime_use_autosuspend(bank->dev);
> +	pm_runtime_set_autosuspend_delay(bank->dev, GPIO_AUTOSUSPEND_TIMEOUT);
>  	pm_runtime_enable(bank->dev);
>  	pm_runtime_irq_safe(bank->dev);
>  	pm_runtime_get_sync(bank->dev);
> @@ -1146,7 +1152,8 @@ static int __devinit omap_gpio_probe(struct platform_device *pdev)
>  	if (bank->loses_context)
>  		bank->get_context_loss_count = pdata->get_context_loss_count;
>  
> -	pm_runtime_put(bank->dev);
> +	pm_runtime_mark_last_busy(bank->dev);
> +	pm_runtime_put_autosuspend(bank->dev);
>  
>  	list_add_tail(&bank->node, &omap_gpio_list);
>  
> @@ -1333,7 +1340,13 @@ void omap2_gpio_prepare_for_idle(int pwr_mode)
>  
>  		bank->power_mode = pwr_mode;
>  
> -		pm_runtime_put_sync_suspend(bank->dev);
> +		/* direct pm_runtime on pwroff */
> +		if (pwr_mode)

you also need braces here.

> +			pm_runtime_put_sync_suspend(bank->dev);
> +		else {
> +			pm_runtime_mark_last_busy(bank->dev);
> +			pm_runtime_put_sync_autosuspend(bank->dev);
> +		}
>  	}
>  }
>  
> -- 
> 1.7.2.5
> 
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-- 
balbi

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