lkml.org 
[lkml]   [2022]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH v5 2/2] usb: dwc3: core: defer probe on ulpi_read_id timeout
    Date
    On Mon, Dec 05, 2022, Ferry Toth wrote:
    > Since commit 0f0101719138 ("usb: dwc3: Don't switch OTG -> peripheral
    > if extcon is present"), 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() masking the timeout on the first
    > test write. In the past dwc3 probe continued by calling dwc3_core_soft_reset()
    > followed by dwc3_get_extcon() which happend to return -EPROBE_DEFER.
    > On deferred probe ulpi_read_id() finally succeeded. Due to above mentioned
    > rearranging -EPROBE_DEFER is not returned and probe completes without phy.
    >
    > On Intel Merrifield the timeout on the first test write issue is reproducible
    > but it is difficult to find the root cause. Using a mainline kernel and
    > rootfs with buildroot ulpi_read_id() succeeds. As soon as adding
    > ftrace / bootconfig to find out why, ulpi_read_id() fails and we can't
    > analyze the flow. Using another rootfs ulpi_read_id() fails even without
    > adding ftrace. We suspect the issue is some kind of timing / race, but
    > merely retrying ulpi_read_id() does not resolve the issue.
    >
    > As we now changed ulpi_read_id() to return -ETIMEDOUT in this case, we
    > need to handle the error by calling dwc3_core_soft_reset() and request
    > -EPROBE_DEFER. On deferred probe ulpi_read_id() is retried and succeeds.
    >
    > Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")
    > Cc: stable@vger.kernel.org
    > Signed-off-by: Ferry Toth <ftoth@exalondelft.nl>
    > ---
    > drivers/usb/dwc3/core.c | 7 ++++++-
    > 1 file changed, 6 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
    > index 648f1c570021..2779f17bffaf 100644
    > --- a/drivers/usb/dwc3/core.c
    > +++ b/drivers/usb/dwc3/core.c
    > @@ -1106,8 +1106,13 @@ static int dwc3_core_init(struct dwc3 *dwc)
    >
    > if (!dwc->ulpi_ready) {
    > ret = dwc3_core_ulpi_init(dwc);
    > - if (ret)
    > + if (ret) {
    > + if (ret == -ETIMEDOUT) {
    > + dwc3_core_soft_reset(dwc);
    > + ret = -EPROBE_DEFER;
    > + }
    > goto err0;
    > + }
    > dwc->ulpi_ready = true;
    > }
    >
    > --
    > 2.37.2
    >

    Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

    Thanks,
    Thinh
    \
     
     \ /
      Last update: 2022-12-05 22:20    [W:7.650 / U:0.148 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site