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Mon, 26 Feb 2018 10:57:23 -0500 Received: from lelnx194.ext.ti.com ([198.47.27.80]:48383 "EHLO lelnx194.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751947AbeBZP5V (ORCPT ); Mon, 26 Feb 2018 10:57:21 -0500 Date: Mon, 26 Feb 2018 09:57:16 -0600 From: Bin Liu To: Merlijn Wajer CC: , , Greg Kroah-Hartman , , Subject: Re: [PATCH] usb: musb: call pm_runtime_{get,put}_sync before reading vbus registers Message-ID: <20180226155716.GB20609@uda0271908> Mail-Followup-To: Bin Liu , Merlijn Wajer , linux-omap@vger.kernel.org, tony@atomide.com, Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180226105609.22514-1-merlijn@wizzup.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20180226105609.22514-1-merlijn@wizzup.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-usb-owner@vger.kernel.org X-Mailing-List: linux-usb@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hi, On Mon, Feb 26, 2018 at 11:56:08AM +0100, Merlijn Wajer wrote: > Without pm_runtime_{get,put}_sync calls in place, reading > vbus status via /sys causes the following error: > > Unhandled fault: external abort on non-linefetch (0x1028) at 0xfa0ab060 > pgd = b333e822 > [fa0ab060] *pgd=48011452(bad) > > [] (musb_default_readb) from [] (musb_vbus_show+0x58/0xe4) > [] (musb_vbus_show) from [] (dev_attr_show+0x20/0x44) > [] (dev_attr_show) from [] (sysfs_kf_seq_show+0x80/0xdc) > [] (sysfs_kf_seq_show) from [] (seq_read+0x250/0x448) > [] (seq_read) from [] (__vfs_read+0x1c/0x118) > [] (__vfs_read) from [] (vfs_read+0x90/0x144) > [] (vfs_read) from [] (SyS_read+0x3c/0x74) > [] (SyS_read) from [] (ret_fast_syscall+0x0/0x54) > > Solution was suggested by Tony Lindgren . > > Signed-off-by: Merlijn Wajer > --- > drivers/usb/musb/musb_core.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c > index eef4ad578b31..ceaa40ef0e73 100644 > --- a/drivers/usb/musb/musb_core.c > +++ b/drivers/usb/musb/musb_core.c > @@ -1760,6 +1760,8 @@ vbus_show(struct device *dev, struct device_attribute *attr, char *buf) > val = musb->a_wait_bcon; > vbus = musb_platform_get_vbus_status(musb); > if (vbus < 0) { > + pm_runtime_get_sync(dev); > + > /* Use default MUSB method by means of DEVCTL register */ > devctl = musb_readb(musb->mregs, MUSB_DEVCTL); > if ((devctl & MUSB_DEVCTL_VBUS) > @@ -1767,6 +1769,8 @@ vbus_show(struct device *dev, struct device_attribute *attr, char *buf) > vbus = 1; > else > vbus = 0; > + > + pm_runtime_put_sync(dev); > } > spin_unlock_irqrestore(&musb->lock, flags); Thanks for the patch, but I got spinlock deadlock when testing it. I think the function pair should be at the outside scope of the spin_lock/unlock, doesn't it? Regards, -Bin.