Re: [PATCH 1/4] usb: phy: twl4030: make runtime pm more reliable.

Tony Lindgren
2015-02-24T20:58:28Z

* NeilBrown <neilb@suse.de> [150223 19:45]:
> A construct like:
>
> if (pm_runtime_suspended(twl->dev))
> pm_runtime_get_sync(twl->dev);
>
> is against the spirit of the runtime_pm interface as it
> makes the internal refcounting useless.
>
> In this case it is also racy, particularly as 'put_autosuspend'
> is use to drop a reference.
> When that happens a timer is started and the device is
> runtime-suspended after the timeout.
> If the above code runs in this window, the device will not be
> found to be suspended so no pm_runtime reference is taken.
> When the timer expires the device will be suspended, which is
> against the intention of the code.
>
> So be more direct is taking and dropping references.
> If twl->linkstat is VBUS_VALID or ID_GROUND, then hold a
> pm_runtime reference, otherwise don't.

Looks good to me, thanks for fixing it. I've tested this series
on beagleboard-xm by plugging and unplugging devices and
switching between host and peripheral mode, things still
idle properly for off-idle. So please feel free to add:

Tested-by: Tony Lindgren <tony@atomide.com>

> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
> drivers/phy/phy-twl4030-usb.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/phy/phy-twl4030-usb.c b/drivers/phy/phy-twl4030-usb.c
> index 8e87f54671f3..97c59074233f 100644
> --- a/drivers/phy/phy-twl4030-usb.c
> +++ b/drivers/phy/phy-twl4030-usb.c
> @@ -536,8 +536,13 @@ static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
>
> mutex_lock(&twl->lock);
> if (status >= 0 && status != twl->linkstat) {
> + status_changed =
> + (twl->linkstat == OMAP_MUSB_VBUS_VALID ||
> + twl->linkstat == OMAP_MUSB_ID_GROUND)
> + !=
> + (status == OMAP_MUSB_VBUS_VALID ||
> + status == OMAP_MUSB_ID_GROUND);
> twl->linkstat = status;
> - status_changed = true;
> }
> mutex_unlock(&twl->lock);
>
> @@ -555,13 +560,10 @@ static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
> */
> if ((status == OMAP_MUSB_VBUS_VALID) ||
> (status == OMAP_MUSB_ID_GROUND)) {
> - if (pm_runtime_suspended(twl->dev))
> - pm_runtime_get_sync(twl->dev);
> + pm_runtime_get_sync(twl->dev);
> } else {
> - if (pm_runtime_active(twl->dev)) {
> - pm_runtime_mark_last_busy(twl->dev);
> - pm_runtime_put_autosuspend(twl->dev);
> - }
> + pm_runtime_mark_last_busy(twl->dev);
> + pm_runtime_put_autosuspend(twl->dev);
> }
> omap_musb_mailbox(status);
> }
> @@ -768,6 +770,10 @@ static int twl4030_usb_remove(struct platform_device *pdev)
>
> /* disable complete OTG block */
> twl4030_usb_clear_bits(twl, POWER_CTRL, POWER_CTRL_OTG_ENAB);
> +
> + if (twl->linkstat == OMAP_MUSB_VBUS_VALID ||
> + twl->linkstat == OMAP_MUSB_ID_GROUND)
> + pm_runtime_put_noidle(twl->dev);
> pm_runtime_mark_last_busy(twl->dev);
> pm_runtime_put(twl->dev);
>
>
>