From: Ferry Toth ftoth@exalondelft.nl
commit 63130462c919ece0ad0d9bb5a1f795ef8d79687e upstream.
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 Acked-by: Thinh Nguyen Thinh.Nguyen@synopsys.com Signed-off-by: Ferry Toth ftoth@exalondelft.nl Link: https://lore.kernel.org/r/20221205201527.13525-3-ftoth@exalondelft.nl Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/dwc3/core.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/usb/dwc3/core.c +++ b/drivers/usb/dwc3/core.c @@ -914,8 +914,13 @@ static int dwc3_core_init(struct dwc3 *d
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; }