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Mon, 26 Feb 2018 12:20:06 -0500 Subject: Re: [PATCH] usb: musb: call pm_runtime_{get,put}_sync before reading vbus registers To: Bin Liu , 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> From: Merlijn Wajer Message-ID: <73a1de6d-6bf4-275f-aee3-85699cd6ca76@wizzup.org> Date: Mon, 26 Feb 2018 18:19:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux armv7l; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180226155716.GB20609@uda0271908> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="v7DLODj7yyMXF0yaV8OWKW7IM7rys82oW" 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: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --v7DLODj7yyMXF0yaV8OWKW7IM7rys82oW Content-Type: multipart/mixed; boundary="ZxcOfYQgk538GczIH3XlQ1XTQx1BbNV8o"; protected-headers="v1" From: Merlijn Wajer To: Bin Liu , linux-omap@vger.kernel.org, tony@atomide.com, Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <73a1de6d-6bf4-275f-aee3-85699cd6ca76@wizzup.org> Subject: Re: [PATCH] usb: musb: call pm_runtime_{get,put}_sync before reading vbus registers References: <20180226105609.22514-1-merlijn@wizzup.org> <20180226155716.GB20609@uda0271908> In-Reply-To: <20180226155716.GB20609@uda0271908> --ZxcOfYQgk538GczIH3XlQ1XTQx1BbNV8o Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable Hi, On 26/02/18 16:57, Bin Liu wrote: > Hi, >=20 > 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 0xfa0ab06= 0 >> pgd =3D b333e822 >> [fa0ab060] *pgd=3D48011452(bad) >> >> [] (musb_default_readb) from [] (musb_vbus_show+0x= 58/0xe4) >> [] (musb_vbus_show) from [] (dev_attr_show+0x20/0x= 44) >> [] (dev_attr_show) from [] (sysfs_kf_seq_show+0x80= /0xdc) >> [] (sysfs_kf_seq_show) from [] (seq_read+0x250/0x4= 48) >> [] (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= =2Ec >> 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_attr= ibute *attr, char *buf) >> val =3D musb->a_wait_bcon; >> vbus =3D musb_platform_get_vbus_status(musb); >> if (vbus < 0) { >> + pm_runtime_get_sync(dev); >> + >> /* Use default MUSB method by means of DEVCTL register */ >> devctl =3D musb_readb(musb->mregs, MUSB_DEVCTL); >> if ((devctl & MUSB_DEVCTL_VBUS) >> @@ -1767,6 +1769,8 @@ vbus_show(struct device *dev, struct device_attr= ibute *attr, char *buf) >> vbus =3D 1; >> else >> vbus =3D 0; >> + >> + pm_runtime_put_sync(dev); >> } >> spin_unlock_irqrestore(&musb->lock, flags); >=20 > 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. Cheers, Merlijn --ZxcOfYQgk538GczIH3XlQ1XTQx1BbNV8o-- --v7DLODj7yyMXF0yaV8OWKW7IM7rys82oW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEARYIAB0WIQRM5LT7NbLF9yb6a/UGN09rynK8WgUCWpRBowAKCRAGN09rynK8 WsJ2AQCFTepleUmO+hp6g2z88hbLON6tpRFFkCLGamoyJkUZigEAiPE6v00LuuOu 8iPD3QEknN21HdFlDE+/WkOPqw9/LAw= =8PVH -----END PGP SIGNATURE----- --v7DLODj7yyMXF0yaV8OWKW7IM7rys82oW--