linux-kernel - Re: [PATCH v2] usb: musb: fix pm

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Date:	Thu, 12 Jan 2012 13:56:02 +0200
From:	Grazvydas Ignotas <notasas@...il.com>
To:	Felipe Contreras <felipe.contreras@...ia.com>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap <linux-omap@...r.kernel.org>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Jarkko Nikula <jarkko.nikula@...mer.com>,
	Felipe Contreras <felipe.contreras@...il.com>,
	stable@...r.kernel.org, Hema HK <hemahk@...com>
Subject: Re: [PATCH v2] usb: musb: fix pm_runtime mismatch

On Mon, Dec 19, 2011 at 10:01 PM, Felipe Contreras
<felipe.contreras@...ia.com> wrote:
> From: Felipe Contreras <felipe.contreras@...il.com>
>
> In musb_init_controller() there's a pm_runtime_put(), but there's no
> pm_runtime_get(), which creates a mismatch that causes the driver to
> sleep when it shouldn't.

This patch is causing problems here, the device never suspends, I've
verified musb_runtime_suspend and omap2430_runtime_suspend are never
called in my setup, unless I revert this patch. I'm using musb with
ethernet gadget; cable removal also doesn't suspend musb.

It seems pm_runtime_put() that was removed was balancing out
pm_runtime_get in musb_platform_init(), which is called at the
beginning of musb_init_controller(). I think this pm_runtime_get()
from musb_platform_init() should be moved to musb_init_controller() to
stop confusing people and pm_runtime_put() needs to be brought back. I
can do a patch if nobody objects.

> This was introduced in 7acc619[1], but it wasn't triggered in my setup
> until 18a2689[2] was merged to Linus' branch at point df0914[3]. IOW;
> when PM is working as it was supposed to.
>
> However, it seems most of the time this is used in a way that keeps the
> counter above 0, so nobody noticed. Also, it seems to depend on the
> configuration used in versions before 3.1, but not later (or in it).
>
> I found the problem by loading isp1704_charger before any usb gadgets:
> http://article.gmane.org/gmane.linux.kernel/1226122

isp1704_charger seems to be doing otg_io_read(), and it's perfectly
normal that musb can be suspended at the time isp1704 decides to do
this. I think proper fix is to wake up must on musb_ulpi_read() and
musb_ulpi_write() instead.

>
> All versions after 2.6.39 are affected.
>
> [1] usb: musb: Idle path retention and offmode support for OMAP3
> [2] OMAP2+: musb: hwmod adaptation for musb registration
> [3] Merge branch 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6
>
> Cc: stable@...r.kernel.org
> Cc: Hema HK <hemahk@...com>
> Signed-off-by: Felipe Contreras <felipe.contreras@...il.com>
> ---
>  drivers/usb/musb/musb_core.c |    2 --
>  1 files changed, 0 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
> index b63ab15..920f04e 100644
> --- a/drivers/usb/musb/musb_core.c
> +++ b/drivers/usb/musb/musb_core.c
> @@ -2012,8 +2012,6 @@ musb_init_controller(struct device *dev, int nIrq, void __iomem *ctrl)
>        if (status < 0)
>                goto fail3;
>
> -       pm_runtime_put(musb->controller);
> -
>        status = musb_init_debugfs(musb);
>        if (status < 0)
>                goto fail4;
> --
> 1.7.8
>
> --
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-- 
Gražvydas
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