On Mon, Jan 8, 2018 at 10:36 AM, Stefan Wahren <stefan.wahren@xxxxxxxx> wrote: > Am 08.01.2018 um 10:27 schrieb Arnd Bergmann: >> >> On Mon, Jan 8, 2018 at 10:15 AM, Stefan Wahren <stefan.wahren@xxxxxxxx> >> wrote: >>> >>> Hi Eric, >>> Am 07.01.2018 um 23:08 schrieb Eric Anholt: >>>> >>>> Stefan Wahren <stefan.wahren@xxxxxxxx> writes: >>>> >>>>> This reverts commit 014d6da6cb2525d7f48fb08c705cb130cc7b5f4a. >>>>> >>>>> The DT clean up could trigger an endless deferred probe of DWC2 USB >>>>> driver >>>>> on the Raspberry Pi 2/3. So revert the change until we fixed the >>>>> probing >>>>> issue. >>>> >>>> Why's that? I found that I needed to enable the generic no-op phy >>>> driver, but other than that it was fine. >>> >>> >>> in order to avoid this regression. Changing the configuration is not a >>> solution for the kernelci guys. >>> >>> Btw >>> >>> CONFIG_NOP_USB_XCEIV=y >>> >>> is already enabled in arm64/defconfig and the issue still occured. Do you >>> mean a different option? >> >> Obviously we need to fix this, but I really want to understand what >> exactly >> happened so we can fix the code if possible rather than making the >> dts file incompatible with the binding again. > > > i fully agree, but dwc2 "hacking" usually requires more time than reverting > this change. > >> >> Do you have any more insight into how we get into the deferred probe >> situation? > > > I send this bug report [1] on Friday to linux-usb. > > Stefan > > [1] - https://marc.info/?l=linux-usb&m=151518314314753&w=2 Ok, I looked at the code now and it seems that the generic phy layer returns -EINVAL for a phy reference to an invalid node, but not a reference to a valid node without a driver, here it returns -EPROBE_DEFER, which by itself is reasonable behavior. In this case, the NOP_USB_XCEIV driver is using the old usb-phy framework, and the dwc2 driver tries both but bails out when the generic phy returns -EPROBE_DEFER. It sounds like the problem is not limited to raspberry pi then, but the same thing would happen on any other machine using the same algorithm. I looked at the other USB drivers that support both generic-phy and usb-phy drivers: - the generic usb-hcd code (usb_add_hcd) tries usb-phy first and then tries generic-phy, but appears to also return with -EPROBE_DEFER if either of the two asks for deferral. other return codes are ignored. - dwc2 (as show above) tries generic-phy first, propagates -EPROBE_DEFER before trying usb-phy. - dwc3 tries usb-phy first, and propagates -EPROBE_DEFER from generic-phy even if usb-phy had succeeded. - chipidea tries both and uses whichever one works, returning -EPROBE_DEFER as long as both fail. - musb/da8xx_probe propagates any error from generic-phy including -EPROBE_DEFER, it then registers a generic phy and uses that internally. - musb/musb_dsps tries both, it fails if usb-phy is not working, but ignores errors from generic-phy - musb/omap2430 needs both usb-phy and generic-phy - musb/sunxi needs a generic-phy and then registers a usb-phy - renesas_usbhs tries both if they are enabled and fails if one of them returns any error. It's hard to tell what exactly is affected by the usb-hcd change, most importantly since this is configuration dependent: if the generic-phy layer is disabled, nothing changes, but otherwise it would be broken the same way as dwc2 and dwc3. The best idea I have so far is to had a hack into the generic phy code with a full list of compatible strings that the must never return -EPROBE_DEFER because that would break the usb-phy handling: diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c index b4964b067aec..6b9c3a1e7ce5 100644 --- a/drivers/phy/phy-core.c +++ b/drivers/phy/phy-core.c @@ -387,6 +387,24 @@ int phy_calibrate(struct phy *phy) } EXPORT_SYMBOL_GPL(phy_calibrate); +static struct of_device_id legacy_usbphy[] = { + { .compatible = "fsl,imx23-usbphy" }, + { .compatible = "fsl,imx6q-usbphy" }, + { .compatible = "fsl,imx6sl-usbphy" }, + { .compatible = "fsl,imx6sx-usbphy" }, + { .compatible = "fsl,imx6ul-usbphy" }, + { .compatible = "fsl,vf610-usbphy" }, + { .compatible = "nvidia,tegra20-usb-phy" }, + { .compatible = "nvidia,tegra30-usb-phy" }, + { .compatible = "nxp,isp1301" }, + { .compatible = "ti,am335x-usb-ctrl-module" }, + { .compatible = "ti,am335x-usb-phy" }, + { .compatible = "ti,keystone-usbphy" }, + { .compatible = "ti,twl6030-usb" }, + { .compatible = "usb-nop-xceiv" }, + {}, +}; + /** * _of_phy_get() - lookup and obtain a reference to a phy by phandle * @np: device_node for which to get the phy @@ -410,6 +428,15 @@ static struct phy *_of_phy_get(struct device_node *np, int index) if (ret) return ERR_PTR(-ENODEV); + /* + * Some USB host controllers use a "phys" property to refer to + * a device that does not have a generic phy driver but that + * has a driver for the older usb-phy framework. + * We must not return -EPROBE_DEFER for those, so bail out early. + */ + if (of_match_node(legacy_usbphy, args.np)) + return ERR_PTR(-ENODEV); + mutex_lock(&phy_provider_mutex); phy_provider = of_phy_provider_lookup(args.np); if (IS_ERR(phy_provider) || !try_module_get(phy_provider->owner)) { Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
