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Message-ID: <20221118235512.h44h24lpisbw4r7u@synopsys.com>
Date: Fri, 18 Nov 2022 23:55:22 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Ferry Toth <fntoth@...il.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Sean Anderson <sean.anderson@...o.com>,
Liu Shixin <liushixin2@...wei.com>,
Andrey Smirnov <andrew.smirnov@...il.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read_id
timeout
On Fri, Nov 18, 2022, Ferry Toth wrote:
> 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@...londelft.nl>
> > > > > > ---
> > > > > > 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:
Thanks for the test!
>
> # 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?
>
The check you added seems to fit better for this behavior, which I'd
consider a quirk. We can revisit this change if the ulpi update doesn't
go through.
Thanks,
Thinh
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