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Mon, 26 Feb 2018 12:38:40 -0500 Received: from fllnx209.ext.ti.com ([198.47.19.16]:27491 "EHLO fllnx209.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751676AbeBZRih (ORCPT ); Mon, 26 Feb 2018 12:38:37 -0500 Date: Mon, 26 Feb 2018 11:38:33 -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: <20180226173833.GC20609@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> <20180226155716.GB20609@uda0271908> <73a1de6d-6bf4-275f-aee3-85699cd6ca76@wizzup.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <73a1de6d-6bf4-275f-aee3-85699cd6ca76@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: On Mon, Feb 26, 2018 at 06:19:30PM +0100, Merlijn Wajer wrote: > Hi, > > On 26/02/18 16:57, Bin Liu wrote: > > 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? > > I see - sorry. Weird, it worked for me on my Nokia N900. What did you > test this on? > > I will try to submit an improved version tonight (you seem to have a > good idea on what is wrong, so I will follow that), but it would help me > if I can reproduce the issue. I tested on both Beaglebone Black and AM335x GP EVM, on the USB1 host port. I didn't test the USB0 port (yet). Thanks, -Bin.