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

From: Jeffrey Hugo
Date: Wed Jun 05 2019 - 10:11:59 EST

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

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

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

This implementation only affects ACPI based platforms. When booting
with DT, the description in that DT related document is still

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@xxxxxxxxxx>
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.