Re: [PATCH 7/8] usb: dwc3: qcom: Start USB in 'host mode' on the SDM845

Jeffrey Hugo
2019-06-05T14:07:59Z

On 6/5/2019 2:34 AM, Lee Jones wrote:
> On Wed, 05 Jun 2019, Bjorn Andersson wrote:
>
>> On Tue 04 Jun 03:44 PDT 2019, Lee Jones wrote:
>>
>>> When booting with Device Tree, the current default boot configuration
>>> table option, the request to boot via 'host mode' comes from the
>>> "dr_mode" property.
>>
>> This has been the default on the MTP, but this is changing as this is
>> causing issues when connected downstream from a hub (the typical
>> development case for the primary USB port of a phone like device) and
>> more importantly we don't have support for the PMIC blocks that control
>> VBUS.
>
> My point is not about which mode is currently chosen. It's more about
> the capability of choosing which mode is appropriate for a given
> system via DT.
>
>> Once these issues are resolved the dr_mode would be "otg".
>
> OTG doesn't work on this H/W, so we need to specify "host" mode.

How have you made that determination?

>
>>> A property of the same name can be used inside
>>> ACPI tables too. However it is missing from the SDM845's ACPI tables
>>> so we have to supply this information using Platform Device Properites
>>> instead.
>>>
>>
>> Afaict this would install a fall-back property, so in the case that we
>> have specified dr_mode in DT (or ACPI) that would take precedence. So
>
> That's correct.
>
>> the commit message should reflect that this redefines the default choice
>> to be "host", rather than "otg".
>
> No problem. >
>> Which is in conflict with what's described for dr_mode in
>> Documentation/devicetree/bindings/usb/generic.txt
>
> This implementation only affects ACPI based platforms. When booting
> with DT, the description in that DT related document is still
> accurate.
>
>> And this driver is used on a range of different Qualcomm platforms, so I
>> don't think this is SDM845 specific.
>
> ACPI based platforms?
>
> All the ones I've seen use the XHCI USB driver directly ("PNP0D10").
>
>>> Signed-off-by: Lee Jones <lee.jones@linaro.org>
>>> ---
>>> drivers/usb/dwc3/dwc3-qcom.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
>>> index 349bf549ee44..f21fdd6cdd1a 100644
>>> --- a/drivers/usb/dwc3/dwc3-qcom.c
>>> +++ b/drivers/usb/dwc3/dwc3-qcom.c
>>> @@ -468,6 +468,11 @@ static const struct acpi_device_id dwc3_qcom_acpi_match[] = {
>>> };
>>> MODULE_DEVICE_TABLE(acpi, dwc3_qcom_acpi_match);
>>>
>>> +static const struct property_entry dwc3_qcom_acpi_properties[] = {
>>> + PROPERTY_ENTRY_STRING("dr_mode", "host"),
>>> + {}
>>> +};
>>> +
>>> static int dwc3_qcom_probe(struct platform_device *pdev)
>>> {
>>> struct device_node *np = pdev->dev.of_node, *dwc3_np;
>>> @@ -603,6 +608,13 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
>>> goto platform_unalloc;
>>> }
>>>
>>> + ret = platform_device_add_properties(qcom->dwc3,
>>> + dwc3_qcom_acpi_properties);
>>> + if (ret < 0) {
>>> + dev_err(&pdev->dev, "failed to add properties\n");
>>> + goto platform_unalloc;
>>> + }
>>> +
>>> ret = platform_device_add(qcom->dwc3);
>>> if (ret) {
>>> dev_err(&pdev->dev, "failed to add device\n");
>

--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.