Subject: [PATCH v6 09/16] OMAP2+: UART: Add runtime pm support for omap-serial driver

From: [email-masked] (Kevin Hilman)
Date: Wed, 12 Oct 2011 17:06:43 -0700

"Govindraj.R" <[email-masked]> writes:

[...] 

> Use device_may_wakeup to check whether uart has wakeup capabilities
> and then enable uart runtime usage for the uart.

Curious about what happens when device_may_wakeup() is not set during
device init.

[...]

> @@ -1305,6 +1363,16 @@ static int serial_omap_probe(struct platform_device *pdev)
>  		up->uart_dma.rx_dma_channel = OMAP_UART_DMA_CH_FREE;
>  	}
>  
> +	pm_runtime_use_autosuspend(&pdev->dev);
> +	pm_runtime_set_autosuspend_delay(&pdev->dev,
> +			OMAP_UART_AUTOSUSPEND_DELAY);
> +
> +	pm_runtime_irq_safe(&pdev->dev);
> +	if (device_may_wakeup(&pdev->dev)) {
> +		pm_runtime_enable(&pdev->dev);

So if device_may_wakeup() is false, runtime PM is not enabled, then...

> +		pm_runtime_get_sync(&pdev->dev);

...this get doesn't happen, and the first register access causes a crash.

So either this get isn't needed, because there is no device access in
this path, or this path is broken and needs validation.

> +	}
> +
>  	ui[pdev->id] = up;
>  	serial_omap_add_console_port(up);
>  
> @@ -1312,6 +1380,7 @@ static int serial_omap_probe(struct platform_device *pdev)
>  	if (ret != 0)
>  		goto do_release_region;
>  
> +	pm_runtime_put(&pdev->dev);

...also, this put is not balanced with a corresponding get.

Kevin