Re: [PATCH v7 2/4] usb: dwc3: qcom: Add interconnect support in dwc3 driver
From: Stephen Boyd <hidden>
Date: 2020-06-03 17:42:48
Also in:
linux-arm-msm, linux-usb, lkml
Quoting Sandeep Maheswaram (2020-03-31 22:15:43)
quoted hunk ↗ jump to hunk
diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c index 1dfd024..d33ae86 100644 --- a/drivers/usb/dwc3/dwc3-qcom.c +++ b/drivers/usb/dwc3/dwc3-qcom.c@@ -76,8 +85,13 @@ struct dwc3_qcom { enum usb_dr_mode mode; bool is_suspended; bool pm_suspended; + struct icc_path *usb_ddr_icc_path; + struct icc_path *apps_usb_icc_path; }; +static int dwc3_qcom_interconnect_enable(struct dwc3_qcom *qcom); +static int dwc3_qcom_interconnect_disable(struct dwc3_qcom *qcom);
Please get rid of these. We shouldn't need forward declarations.
quoted hunk ↗ jump to hunk
+ static inline void dwc3_qcom_setbits(void __iomem *base, u32 offset, u32 val) { u32 reg;@@ -285,6 +307,101 @@ static int dwc3_qcom_resume(struct dwc3_qcom *qcom) return 0; } + +/** + * dwc3_qcom_interconnect_init() - Get interconnect path handles + * @qcom: Pointer to the concerned usb core. + * + */ +static int dwc3_qcom_interconnect_init(struct dwc3_qcom *qcom) +{ + struct device *dev = qcom->dev; + int ret; + + if (!device_is_bound(&qcom->dwc3->dev)) + return -EPROBE_DEFER;
How is this supposed to work? I see that this was added in an earlier revision of this patch series but there isn't any mention of why device_is_bound() is used here. It would be great if there was a comment detailing why this is necessary. It sounds like maximum_speed is important? Furthermore, dwc3_qcom_interconnect_init() is called by dwc3_qcom_probe() which is the function that registers the device for qcom->dwc3->dev. If that device doesn't probe between the time it is registered by dwc3_qcom_probe() and this function is called then we'll fail dwc3_qcom_probe() with -EPROBE_DEFER. And that will remove the qcom->dwc3->dev device from the platform bus because we call of_platform_depopulate() on the error path of dwc3_qcom_probe(). So isn't this whole thing racy and can potentially lead us to a driver probe loop where the wrapper (dwc3_qcom) and the core (dwc3) are probing and we're trying to time it just right so that driver for dwc3 binds before we setup interconnects? I don't know if dwc3 can communicate to the wrapper but that would be more of a direct way to do this. Or maybe the wrapper should try to read the DT property for maximum speed and fallback to a worst case high bandwidth value if it can't figure it out itself without help from dwc3 core.