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    Subject[PATCH 4.4 126/268] usb: musb: call pm_runtime_{get,put}_sync before reading vbus registers
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Merlijn Wajer <merlijn@wizzup.org>

    [ Upstream commit df6b074dbe248d8c43a82131e8fd429e401841a5 ]

    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)

    [<c05261b0>] (musb_default_readb) from [<c0525bd0>] (musb_vbus_show+0x58/0xe4)
    [<c0525bd0>] (musb_vbus_show) from [<c04c0148>] (dev_attr_show+0x20/0x44)
    [<c04c0148>] (dev_attr_show) from [<c0259f74>] (sysfs_kf_seq_show+0x80/0xdc)
    [<c0259f74>] (sysfs_kf_seq_show) from [<c0210bac>] (seq_read+0x250/0x448)
    [<c0210bac>] (seq_read) from [<c01edb40>] (__vfs_read+0x1c/0x118)
    [<c01edb40>] (__vfs_read) from [<c01edccc>] (vfs_read+0x90/0x144)
    [<c01edccc>] (vfs_read) from [<c01ee1d0>] (SyS_read+0x3c/0x74)
    [<c01ee1d0>] (SyS_read) from [<c0106fe0>] (ret_fast_syscall+0x0/0x54)

    Solution was suggested by Tony Lindgren <tony@atomide.com>.

    Signed-off-by: Merlijn Wajer <merlijn@wizzup.org>
    Acked-by: Tony Lindgren <tony@atomide.com>
    Signed-off-by: Bin Liu <b-liu@ti.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/usb/musb/musb_core.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/usb/musb/musb_core.c
    +++ b/drivers/usb/musb/musb_core.c
    @@ -1775,6 +1775,7 @@ musb_vbus_show(struct device *dev, struc
    int vbus;
    u8 devctl;

    + pm_runtime_get_sync(dev);
    spin_lock_irqsave(&musb->lock, flags);
    val = musb->a_wait_bcon;
    vbus = musb_platform_get_vbus_status(musb);
    @@ -1788,6 +1789,7 @@ musb_vbus_show(struct device *dev, struc
    vbus = 0;
    }
    spin_unlock_irqrestore(&musb->lock, flags);
    + pm_runtime_put_sync(dev);

    return sprintf(buf, "Vbus %s, timeout %lu msec\n",
    vbus ? "on" : "off", val);

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