From: Stephen Boyd <swboyd@chromium.org>
To: Andy Gross <agross@kernel.org>, Felipe Balbi <balbi@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Matthias Kaehlcke <mka@chromium.org>
Cc: linux-arm-msm@vger.kernel.org,
Manu Gautam <mgautam@codeaurora.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Sandeep Maheswaram <sanm@codeaurora.org>,
Doug Anderson <dianders@chromium.org>,
Matthias Kaehlcke <mka@chromium.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>
Subject: Re: [PATCH] usb: dwc3: qcom: Make sure core device is fully initialized before it is used
Date: Wed, 17 Jun 2020 12:49:13 -0700 [thread overview]
Message-ID: <159242335325.62212.8113067612959846891@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <20200616133734.1.I1902d0d48e4f3d4c5b5f1a2008108a4cd3c5ddb5@changeid>
Quoting Matthias Kaehlcke (2020-06-16 13:37:37)
> dwc3_qcom_of_register_core() uses of_platform_populate() to add
> the dwc3 core device. The driver core will try to probe the device,
> however this might fail (e.g. due to deferred probing) and
> of_platform_populate() would still return 0 if the device was
> successully added to the platform bus. Verify that the core device
> is actually bound to its driver before using it, defer probing of the
> dwc3_qcom device if the core device isn't ready (yet).
>
> Fixes: a4333c3a6ba9 ("usb: dwc3: Add Qualcomm DWC3 glue driver").
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> ---
> depends on:
> https://lore.kernel.org/patchwork/patch/1251661/ ("driver core:Export
> the symbol device_is_bound")
>
> drivers/usb/dwc3/dwc3-qcom.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index 1dfd024cd06b..5a9036b050c6 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -537,6 +537,16 @@ static int dwc3_qcom_of_register_core(struct platform_device *pdev)
> return -ENODEV;
> }
>
> + /*
> + * A successful return from of_platform_populate() only guarantees that
> + * the core device was added to the platform bus, however it might not
> + * be bound to its driver (e.g. due to deferred probing). This driver
> + * requires the core device to be fully initialized, so defer probing
> + * if it isn't ready (yet).
> + */
> + if (!device_is_bound(&qcom->dwc3->dev))
> + return -EPROBE_DEFER;
Isn't this still broken? i.e. the dwc3 core driver may bind much later
and then device_is_bound() will return an error here and then we'll
return to the caller, dwc3_qcom_probe(), and that will depopulate the
device with of_platform_depopulate(). It seems like we need to run some
sort of wait for driver to be bound function instead of a one-shot check
for the driver being bound.
> +
> return 0;
Also, what about acpi? That has the same problem but it isn't covered by
the dwc3_qcom_of_register_core() function.
next prev parent reply other threads:[~2020-06-17 19:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 20:37 [PATCH] usb: dwc3: qcom: Make sure core device is fully initialized before it is used Matthias Kaehlcke
2020-06-17 5:35 ` Bjorn Andersson
2020-06-17 19:49 ` Stephen Boyd [this message]
2020-06-17 21:24 ` Matthias Kaehlcke
2020-06-21 5:50 ` kernel test robot
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