Re: [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read_id timeout
From: Ferry Toth
Date: Fri Nov 18 2022 - 17:29:49 EST
Hi,
Op 11-11-2022 om 02:31 schreef Thinh Nguyen:
On Thu, Nov 10, 2022, Ferry Toth wrote:
Hi
Op 10-11-2022 om 13:45 schreef Ferry Toth:
(sorry sent html with previous attempt)
On 10-11-2022 01:06, Thinh Nguyen wrote:
Hi Ferry,
On Wed, Nov 09, 2022, Ferry Toth wrote:
Since commit 0f010171
Dual Role support on Intel Merrifield platform broke due to rearranging
the call to dwc3_get_extcon().
It appears to be caused by ulpi_read_id() on the first test
write failing
with -ETIMEDOUT. Currently ulpi_read_id() expects to discover
the phy via
DT when the test write fails and returns 0 in that case even if
DT does not
provide the phy. Due to the timeout being masked dwc3 probe continues by
calling dwc3_core_soft_reset() followed by dwc3_get_extcon()
which happens
to return -EPROBE_DEFER. On deferred probe ulpi_read_id()
finally succeeds.
This patch changes ulpi_read_id() to return -ETIMEDOUT when it
occurs and
catches the error in dwc3_core_init(). It handles the error by calling
dwc3_core_soft_reset() after which it requests -EPROBE_DEFER. On
deferred
probe ulpi_read_id() again succeeds.
Signed-off-by: Ferry Toth<ftoth@xxxxxxxxxxxxxx>
---
drivers/usb/common/ulpi.c | 5 +++--
drivers/usb/dwc3/core.c | 5 ++++-
2 files changed, 7 insertions(+), 3 deletions(-)
Can you split the dwc3 change and ulpi change to separate patches?
Thanks for your comments.
I will send v2
diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
index d7c8461976ce..d8f22bc2f9d0 100644
--- a/drivers/usb/common/ulpi.c
+++ b/drivers/usb/common/ulpi.c
@@ -206,8 +206,9 @@ static int ulpi_read_id(struct ulpi *ulpi)
/* Test the interface */
ret = ulpi_write(ulpi, ULPI_SCRATCH, 0xaa);
- if (ret < 0)
- goto err;
+ if (ret < 0) {
+ return ret;
+ }
ret = ulpi_read(ulpi, ULPI_SCRATCH);
if (ret < 0)
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 648f1c570021..e293ef70039b 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1106,8 +1106,11 @@ static int dwc3_core_init(struct dwc3 *dwc)
if (!dwc->ulpi_ready) {
ret = dwc3_core_ulpi_init(dwc);
- if (ret)
+ if (ret) {
+ dwc3_core_soft_reset(dwc);
We shouldn't need to do soft reset here. The controller shouldn't be at
a bad/incorrect state at this point to warrant a soft-reset. There will
be a soft-reset when it goes through the initialization again.
It doesn't go through the initialization again unless we set
-EPROBE_DEFER. And when we make ulpi_read_id() return -EPROBE_DEFER it
will goto err0 here, so skips dwc3_core_soft_reset.
Do you mean you prefer something like:
if (ret) {
if (ret == -ETIMEDOUT) ret = -EPROBE_DEFER;
else goto err0;
Why "else"? But I saw you remove that in the new patch.
}
I just tested, and calling dwc3_core_soft_reset() proves to be necessary as
we need to goto err0 directly after. Else ret is overwritten and
-EPROBE_DEFER lost.
Looks like there's a strange dependency problem here.
* The setup needs a soft-reset before ulpi registration
* The ulpi registration needs to go before the phy initialization
* The soft-reset should be called after the phy initialization
I can't explain the actual issue here, and we can't debug further
because to look into it further would require looking at internal
signals.
This soft-reset and -EPROBE_DEFER seems to be a workaround to this
dependency problem. Instead of using -EPROBE_DEFER, can you do this:
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 2f0a9679686f..5a1aaf3741ec 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1097,6 +1097,8 @@ static int dwc3_core_init(struct dwc3 *dwc)
goto err0;
if (!dwc->ulpi_ready) {
+ /* Add comment */
+ dwc3_core_soft_reset(dwc);
ret = dwc3_core_ulpi_init(dwc);
if (ret)
goto err0;
This indeed fixes the issue as well. Here is the trace:
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
0) | /* start_event: (dwc3_probe+0x0/0x1910) */
0) 7.070 us | dwc3_clk_enable.part.0();
0) 5.480 us | extcon_get_extcon_dev();
0) + 10.230 us | dwc3_runtime_idle();
0) | /* end_event: (platform_probe+0x3f/0xa0 <-
dwc3_probe) */
** multiple defers while waiting for extcon
0) | /* start_event: (dwc3_probe+0x0/0x1910) */
0) 7.320 us | dwc3_clk_enable.part.0();
0) 6.830 us | extcon_get_extcon_dev();
0) | dwc3_core_init() {
0) + 29.200 us | dwc3_core_soft_reset.part.0();
0) | dwc3_ulpi_init() {
0) | ulpi_register_interface() {
0) | dwc3_ulpi_write() {
0) 3.380 us | dwc3_ulpi_busyloop();
** without this patch this one times out after 10000us
0) 7.710 us | }
0) | dwc3_ulpi_read() {
0) 3.060 us | dwc3_ulpi_busyloop();
0) 7.210 us | }
0) | dwc3_ulpi_read() {
0) 2.830 us | dwc3_ulpi_busyloop();
0) 6.690 us | }
0) | dwc3_ulpi_read() {
0) 2.880 us | dwc3_ulpi_busyloop();
0) 6.670 us | }
0) | dwc3_ulpi_read() {
0) 2.940 us | dwc3_ulpi_busyloop();
0) 6.690 us | }
0) | dwc3_ulpi_read() {
0) 2.870 us | dwc3_ulpi_busyloop();
0) 6.620 us | }
0) + 18.150 us | ulpi_uevent();
0) 5.990 us | ulpi_match();
0) | ulpi_probe() {
0) | tusb1210_probe() {
0) | ulpi_read() {
0) | dwc3_ulpi_read() {
0) 4.440 us | dwc3_ulpi_busyloop();
0) 9.600 us | }
0) + 15.770 us | }
0) | ulpi_write() {
0) | dwc3_ulpi_write() {
0) 3.270 us | dwc3_ulpi_busyloop();
0) 6.820 us | }
0) + 11.020 us | }
0) ! 407.540 us | }
0) ! 416.980 us | }
0) 9.800 us | ulpi_uevent();
0) * 18604.00 us | }
0) * 18611.20 us | }
0) + 30.570 us | dwc3_core_soft_reset.part.0();
0) | tusb1210_power_on() {
1) | extcon_set_state_sync() {
1) 5.330 us | extcon_set_state.part.0();
1) + 90.550 us | extcon_sync.part.0();
1) ! 113.670 us | }
1) + 19.450 us | ulpi_uevent();
0) + 13.640 us | ulpi_uevent();
1) + 13.980 us | ulpi_uevent();
0) + 15.960 us | ulpi_uevent();
0) | ulpi_write() {
0) | dwc3_ulpi_write() {
0) * 10239.47 us | dwc3_ulpi_busyloop();
0) * 10250.57 us | }
0) * 10265.09 us | }
0) * 69518.95 us | }
0) 5.740 us | dwc3_event_buffers_setup();
0) * 88241.02 us | } /* dwc3_core_init */
0) ! 104.900 us | dwc3_debugfs_init();
0) | dwc3_drd_init() {
0) 4.720 us | extcon_register_notifier();
0) | extcon_get_state() {
0) 2.640 us | extcon_get_state.part.0();
0) 6.460 us | }
0) + 14.460 us | dwc3_set_mode();
0) + 43.300 us | }
0) | /* end_event: (platform_probe+0x3f/0xa0 <-
dwc3_probe) */
Maybe this is the preferred way to go if the dwc3_core_soft_reset()
doesn't hurt other users?
+ ret = -EPROBE_DEFER;
We shouldn't automatically set every error status to correspond to
-EPROBE_DEFER. Check only the approapriate error codes (-ETIMEDOUT +
any other?).
Other could be -ENOMEM. I think no need to do any new handling for that.
There's also -EINVAL and some others too. Regardless, if it's -ENOMEM,
then it should not return -EPROBE_DEFER.
goto err0;
+ }
dwc->ulpi_ready = true;
}
Thanks,
Thinh