Hi,
On 08-09-16 12:24, Chen-Yu Tsai wrote:
On Thu, Sep 8, 2016 at 6:16 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Hi,
On 08-09-16 05:14, Chen-Yu Tsai wrote:
The musb driver calls into this phy driver to disable/enable squelch
detection. This function was introduced in 24fe86a617c5 ("phy: sun4i-usb:
Add a sunxi specific function for setting squelch-detect"). This
function in turn calls sun4i_usb_phy_write, which uses a mutex to
guard the common access register. Unfortunately musb does this
in atomic context, which results in the following warning with lock
debugging enabled:
BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:97
in_atomic(): 1, irqs_disabled(): 128, pid: 96, name: kworker/0:2
CPU: 0 PID: 96 Comm: kworker/0:2 Not tainted 4.8.0-rc4-00181-gd502f8ad1c3e
#13
Hardware name: Allwinner sun8i Family
Workqueue: events musb_deassert_reset
[<c010bc01>] (unwind_backtrace) from [<c0109237>] (show_stack+0xb/0xc)
[<c0109237>] (show_stack) from [<c02a669b>] (dump_stack+0x67/0x74)
[<c02a669b>] (dump_stack) from [<c05d68c9>] (mutex_lock+0x15/0x2c)
[<c05d68c9>] (mutex_lock) from [<c02c3589>]
(sun4i_usb_phy_write+0x39/0xec)
[<c02c3589>] (sun4i_usb_phy_write) from [<c03e6327>]
(musb_port_reset+0xfb/0x184)
[<c03e6327>] (musb_port_reset) from [<c03e4917>]
(musb_deassert_reset+0x1f/0x2c)
[<c03e4917>] (musb_deassert_reset) from [<c012ecb5>]
(process_one_work+0x129/0x2b8)
[<c012ecb5>] (process_one_work) from [<c012f5e3>]
(worker_thread+0xf3/0x424)
[<c012f5e3>] (worker_thread) from [<c0132dbd>] (kthread+0xa1/0xb8)
[<c0132dbd>] (kthread) from [<c0105f31>] (ret_from_fork+0x11/0x20)
Since the register access is mmio, we can use a spinlock to guard this
specific access, rather than the mutex that guards the entire phy.
Fixes: ba4bdc9e1dc0 ("PHY: sunxi: Add driver for sunxi usb phy")
Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
Good catch, but you're actually replacing the locking calls in the only
user of sun4i_usb_phy_data.mutex, so after your patch it is no longer
used anywhere. Can you do a v2 just outright replacing it with a
spinlock please ?
Ah. I misread the other use of mutex_lock, which is actually using
the mutex in struct phy. Sure I'll just replace it.
After sending this patch I wondered if I should have used
spin_lock_irqsave though.
Good point, yes please use spin_lock_irqsave, I believe this
code path may get called outside of irq handling so using
spin_lock_irqsave is the right thing todo.
Regards,
Hans
ChenYu
Thanks,
Hans
---
drivers/phy/phy-sun4i-usb.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/phy/phy-sun4i-usb.c b/drivers/phy/phy-sun4i-usb.c
index fcf4d95ecc6d..ae4ac5457c64 100644
--- a/drivers/phy/phy-sun4i-usb.c
+++ b/drivers/phy/phy-sun4i-usb.c
@@ -40,6 +40,7 @@
#include <linux/power_supply.h>
#include <linux/regulator/consumer.h>
#include <linux/reset.h>
+#include <linux/spinlock.h>
#include <linux/usb/of.h>
#include <linux/workqueue.h>
@@ -115,6 +116,7 @@ struct sun4i_usb_phy_data {
const struct sun4i_usb_phy_cfg *cfg;
enum usb_dr_mode dr_mode;
struct mutex mutex;
+ spinlock_t reg_lock; /* guard access to phyctl reg */
struct sun4i_usb_phy {
struct phy *phy;
void __iomem *pmu;
@@ -183,7 +185,7 @@ static void sun4i_usb_phy_write(struct sun4i_usb_phy
*phy, u32 addr, u32 data,
void __iomem *phyctl = phy_data->base +
phy_data->cfg->phyctl_offset;
int i;
- mutex_lock(&phy_data->mutex);
+ spin_lock(&phy_data->reg_lock);
if (phy_data->cfg->type == sun8i_a33_phy ||
phy_data->cfg->type == sun50i_a64_phy) {
@@ -221,7 +223,8 @@ static void sun4i_usb_phy_write(struct sun4i_usb_phy
*phy, u32 addr, u32 data,
data >>= 1;
}
- mutex_unlock(&phy_data->mutex);
+
+ spin_unlock(&phy_data->reg_lock);
}
static void sun4i_usb_phy_passby(struct sun4i_usb_phy *phy, int enable)
@@ -583,6 +586,7 @@ static int sun4i_usb_phy_probe(struct platform_device
*pdev)
return -ENOMEM;
mutex_init(&data->mutex);
+ spin_lock_init(&data->reg_lock);
INIT_DELAYED_WORK(&data->detect, sun4i_usb_phy0_id_vbus_det_scan);
dev_set_drvdata(dev, data);
data->cfg = of_device_get_match_data(dev);
--
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