[PATCH v5 1/2] dt-bindings: usb: dwc3: Document Renesas R-Car Gen5 DWC3 xHCI USB controller

[PATCH v5 1/2] dt-bindings: usb: dwc3: Document Renesas R-Car Gen5 DWC3 xHCI USB controller

[Marek Vasut]

The Renesas R-Car Gen5 SoC contains multiple instances of DWC3 USB
controller with glue logic wrapper around them. Document the glue
logic and DWC3 controller.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
Cc: linux-usb@vger.kernel.org
---
V2: Rework to use flat bindings for generic plat driver
V3: - Support one or two PHYs to correctly describe the hardware
    - Make maximum-speed optional
V4: - Use ref: snps,dwc3-common.yaml and drop generic dr_mode/maximum-speed/phys/phy-names
    - Switch to unevaluatedProperties: false
V5: - Limit maximum PHY count to 2
---
 .../bindings/usb/renesas,rcar-gen5-dwc3.yaml  | 76 +++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/usb/renesas,rcar-gen5-dwc3.yaml

diff --git a/Documentation/devicetree/bindings/usb/renesas,rcar-gen5-dwc3.yaml b/Documentation/devicetree/bindings/usb/renesas,rcar-gen5-dwc3.yaml
new file mode 100644
index 0000000000000..c8a770d7e0241
--- /dev/null
+++ b/Documentation/devicetree/bindings/usb/renesas,rcar-gen5-dwc3.yaml
@@ -0,0 +1,76 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/renesas,rcar-gen5-dwc3.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas R-Car Gen5 DWC3 xHCI USB controller
+
+maintainers:
+  - Marek Vasut <marek.vasut+renesas@mailbox.org>
+
+allOf:
+  - $ref: snps,dwc3-common.yaml#
+
+properties:
+  compatible:
+    items:
+      - const: renesas,r8a78000-dwc3
+      - const: renesas,rcar-gen5-dwc3
+
+  reg:
+    maxItems: 2
+
+  reg-names:
+    items:
+      - const: dwc3
+      - const: glue
+
+  clocks:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  phys:
+    minItems: 1
+    maxItems: 2
+
+  phy-names:
+    minItems: 1
+    maxItems: 2
+
+  power-domains:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - clocks
+  - interrupts
+  - phys
+  - phy-names
+  - power-domains
+  - resets
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    usb@c8800000 {
+        compatible = "renesas,r8a78000-dwc3", "renesas,rcar-gen5-dwc3";
+        reg = <0xc8800000 0x100000>, <0xc9c54000 0x2000>;
+        reg-names = "dwc3", "glue";
+        clocks = <&scmi_clk 336>;
+        interrupts = <GIC_SPI 795 IRQ_TYPE_LEVEL_HIGH>;
+        phys = <&usb30_phy>, <&mp_phy 2>;
+        phy-names = "usb2-phy", "usb3-phy";
+        power-domains = <&scmi_devpd 16>;
+        resets = <&scmi_reset 336>;
+    };
-- 
2.53.0

[PATCH v5 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[Marek Vasut]

From: Thanh Quan <thanh.quan.xn@renesas.com>

The Renesas R-Car Gen5 SoC contains multiple instances of DWC3 USB
controller with glue logic wrapper around them. Extend the generic
DWC3 platform driver with Renesas R-Car Gen5 glue logic specifics.

Signed-off-by: Thanh Quan <thanh.quan.xn@renesas.com>
Co-developed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
Cc: linux-usb@vger.kernel.org
---
V2: Extend dwc3-generic-plat driver instead
V3: Handle maximum-speed as optional property, test for USB 3 PHY
    non-presence to determine whether the controller is USB 2 only,
    consider optional maximum-speed DT property, but if it is missing
    then default to maximum controller capabilities based on the
    presence of PHY phandles.
V4: No change
V5: - Drop superfluous code comment
    - Drop duplicate speed >= USB_SPEED_LOW test
---
 drivers/usb/dwc3/dwc3-generic-plat.c | 55 ++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
index ca69ac0eb07ce..3994a6d93b9de 100644
--- a/drivers/usb/dwc3/dwc3-generic-plat.c
+++ b/drivers/usb/dwc3/dwc3-generic-plat.c
@@ -71,6 +71,55 @@ static int dwc3_eic7700_init(struct dwc3_generic *dwc3g)
 	return 0;
 }
 
+static int dwc3_renesas_rcar_gen5_init(struct dwc3_generic *dwc3g)
+{
+	struct device *dev = dwc3g->dev;
+	struct platform_device *pdev = to_platform_device(dev);
+	enum usb_device_speed speed = usb_get_maximum_speed(dev);
+	bool usb2only = false;
+	void __iomem *glue;
+
+	/* Wireless USB is not supported */
+	if (speed == USB_SPEED_WIRELESS)
+		return dev_err_probe(dev, -EINVAL, "Wireless USB not supported\n");
+
+	/* No USB 3 PHY in DT means this is surely USB 2 controller */
+	if (device_property_match_string(dev, "phy-names", "usb3-phy") < 0)
+		usb2only = true;
+
+	if (speed <= USB_SPEED_HIGH)
+		usb2only = true;
+
+	glue = devm_platform_ioremap_resource_byname(pdev, "glue");
+	if (IS_ERR(glue))
+		return PTR_ERR(glue);
+
+	/*
+	 * The datasheet describes initialization procedure without full
+	 * information about the registers. Therefore, the source code is
+	 * based on the bare metal code shared by the board team.
+	 */
+	writew(0x211, glue + 0x26);
+
+	/* USB2 does need additional register programming. */
+	if (!usb2only)
+		return 0;
+
+	writew(0x11, glue + 0x81c);
+	writew(0x0, glue + 0x81a);
+	writew(0x1, glue + 0x802);
+
+	usleep_range(10000, 20000);
+
+	writew(0x0, glue + 0x802);
+	writew(0x1, glue + 0x2a);
+	writew(0x1, glue + 0x81a);
+
+	usleep_range(10000, 20000);
+
+	return 0;
+}
+
 static int dwc3_spacemit_k1_init(struct dwc3_generic *dwc3g)
 {
 	struct device *dev = dwc3g->dev;
@@ -231,11 +280,17 @@ static const struct dwc3_generic_config eic7700_dwc3 =  {
 	.properties = DWC3_DEFAULT_PROPERTIES,
 };
 
+static const struct dwc3_generic_config renesas_rcar_gen5_dwc3 = {
+	.init = dwc3_renesas_rcar_gen5_init,
+	.properties = DWC3_DEFAULT_PROPERTIES,
+};
+
 static const struct of_device_id dwc3_generic_of_match[] = {
 	{ .compatible = "spacemit,k1-dwc3", &spacemit_k1_dwc3},
 	{ .compatible = "spacemit,k3-dwc3", },
 	{ .compatible = "fsl,ls1028a-dwc3", &fsl_ls1028_dwc3},
 	{ .compatible = "eswin,eic7700-dwc3", &eic7700_dwc3},
+	{ .compatible = "renesas,rcar-gen5-dwc3", &renesas_rcar_gen5_dwc3},
 	{ .compatible = "starfive,jhb100-dwc3", },
 	{ /* sentinel */ }
 };
-- 
2.53.0

Re: [PATCH v5 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Missing 'maximum-speed' DT property incorrectly forces the controller into USB 2.0-only mode, overriding PHY-based detection.
--

commit 0727bb2cc9c155e4d5497db94c337bc5b2603464
Author: Thanh Quan <thanh.quan.xn@renesas.com>
usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

This commit extends the generic DWC3 platform driver with glue logic for
Renesas R-Car Gen5 USB controllers. It handles hardware initialization and
evaluates PHY presence alongside device tree properties to determine maximum
supported USB speeds.

> diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
> index ca69ac0eb07ce..3994a6d93b9de 100644
> --- a/drivers/usb/dwc3/dwc3-generic-plat.c
> +++ b/drivers/usb/dwc3/dwc3-generic-plat.c
[ ... ]
> @@ -71,6 +71,55 @@ static int dwc3_eic7700_init(struct dwc3_generic *dwc3g)
>  	return 0;
>  }
>  
> +static int dwc3_renesas_rcar_gen5_init(struct dwc3_generic *dwc3g)
> +{
> +	struct device *dev = dwc3g->dev;
> +	struct platform_device *pdev = to_platform_device(dev);
> +	enum usb_device_speed speed = usb_get_maximum_speed(dev);
> +	bool usb2only = false;
> +	void __iomem *glue;
> +
> +	/* Wireless USB is not supported */
> +	if (speed == USB_SPEED_WIRELESS)
> +		return dev_err_probe(dev, -EINVAL, "Wireless USB not supported\n");
> +
> +	/* No USB 3 PHY in DT means this is surely USB 2 controller */
> +	if (device_property_match_string(dev, "phy-names", "usb3-phy") < 0)
> +		usb2only = true;
> +
> +	if (speed <= USB_SPEED_HIGH)
> +		usb2only = true;

[Severity: High]
Will this condition inadvertently force the controller into USB 2.0 mode when
the maximum-speed property is missing from the device tree?

When the maximum-speed property is absent, usb_get_maximum_speed() returns
USB_SPEED_UNKNOWN, which evaluates to 0. Since 0 is less than USB_SPEED_HIGH,
this condition evaluates to true and unconditionally sets usb2only to true.

This appears to override the preceding logic that correctly checked the
phy-names property to detect USB 3 capabilities. Could this cause hardware
with a USB 3 PHY to be improperly downgraded to USB 2.0 mode?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260828182415.388367-1-marek.vasut+renesas@mailbox.org?part=2

Re: [PATCH v5 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[Marek Vasut]

On 8/28/26 8:30 PM, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] Missing 'maximum-speed' DT property incorrectly forces the controller into USB 2.0-only mode, overriding PHY-based detection.
> --
> 
> commit 0727bb2cc9c155e4d5497db94c337bc5b2603464
> Author: Thanh Quan <thanh.quan.xn@renesas.com>
> usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue
> 
> This commit extends the generic DWC3 platform driver with glue logic for
> Renesas R-Car Gen5 USB controllers. It handles hardware initialization and
> evaluates PHY presence alongside device tree properties to determine maximum
> supported USB speeds.
> 
>> diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
>> index ca69ac0eb07ce..3994a6d93b9de 100644
>> --- a/drivers/usb/dwc3/dwc3-generic-plat.c
>> +++ b/drivers/usb/dwc3/dwc3-generic-plat.c
> [ ... ]
>> @@ -71,6 +71,55 @@ static int dwc3_eic7700_init(struct dwc3_generic *dwc3g)
>>   	return 0;
>>   }
>>   
>> +static int dwc3_renesas_rcar_gen5_init(struct dwc3_generic *dwc3g)
>> +{
>> +	struct device *dev = dwc3g->dev;
>> +	struct platform_device *pdev = to_platform_device(dev);
>> +	enum usb_device_speed speed = usb_get_maximum_speed(dev);
>> +	bool usb2only = false;
>> +	void __iomem *glue;
>> +
>> +	/* Wireless USB is not supported */
>> +	if (speed == USB_SPEED_WIRELESS)
>> +		return dev_err_probe(dev, -EINVAL, "Wireless USB not supported\n");
>> +
>> +	/* No USB 3 PHY in DT means this is surely USB 2 controller */
>> +	if (device_property_match_string(dev, "phy-names", "usb3-phy") < 0)
>> +		usb2only = true;
>> +
>> +	if (speed <= USB_SPEED_HIGH)
>> +		usb2only = true;
> 
> [Severity: High]
> Will this condition inadvertently force the controller into USB 2.0 mode when
> the maximum-speed property is missing from the device tree?
> 
> When the maximum-speed property is absent, usb_get_maximum_speed() returns
> USB_SPEED_UNKNOWN, which evaluates to 0. Since 0 is less than USB_SPEED_HIGH,
> this condition evaluates to true and unconditionally sets usb2only to true.
> 
> This appears to override the preceding logic that correctly checked the
> phy-names property to detect USB 3 capabilities. Could this cause hardware
> with a USB 3 PHY to be improperly downgraded to USB 2.0 mode?

Thinh, maybe I should restore the V4 conditional here ?

Re: [PATCH v5 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[Thinh Nguyen]

Hi Marek,

On Fri, Aug 28, 2026, Marek Vasut wrote:
> On 8/28/26 8:30 PM, sashiko-bot@kernel.org wrote:
> > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > - [High] Missing 'maximum-speed' DT property incorrectly forces the controller into USB 2.0-only mode, overriding PHY-based detection.
> > --
> > 
> > commit 0727bb2cc9c155e4d5497db94c337bc5b2603464
> > Author: Thanh Quan <thanh.quan.xn@renesas.com>
> > usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue
> > 
> > This commit extends the generic DWC3 platform driver with glue logic for
> > Renesas R-Car Gen5 USB controllers. It handles hardware initialization and
> > evaluates PHY presence alongside device tree properties to determine maximum
> > supported USB speeds.
> > 
> > > diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
> > > index ca69ac0eb07ce..3994a6d93b9de 100644
> > > --- a/drivers/usb/dwc3/dwc3-generic-plat.c
> > > +++ b/drivers/usb/dwc3/dwc3-generic-plat.c
> > [ ... ]
> > > @@ -71,6 +71,55 @@ static int dwc3_eic7700_init(struct dwc3_generic *dwc3g)
> > >   	return 0;
> > >   }
> > > +static int dwc3_renesas_rcar_gen5_init(struct dwc3_generic *dwc3g)
> > > +{
> > > +	struct device *dev = dwc3g->dev;
> > > +	struct platform_device *pdev = to_platform_device(dev);
> > > +	enum usb_device_speed speed = usb_get_maximum_speed(dev);
> > > +	bool usb2only = false;
> > > +	void __iomem *glue;
> > > +
> > > +	/* Wireless USB is not supported */
> > > +	if (speed == USB_SPEED_WIRELESS)
> > > +		return dev_err_probe(dev, -EINVAL, "Wireless USB not supported\n");
> > > +
> > > +	/* No USB 3 PHY in DT means this is surely USB 2 controller */
> > > +	if (device_property_match_string(dev, "phy-names", "usb3-phy") < 0)
> > > +		usb2only = true;
> > > +
> > > +	if (speed <= USB_SPEED_HIGH)
> > > +		usb2only = true;
> > 
> > [Severity: High]
> > Will this condition inadvertently force the controller into USB 2.0 mode when
> > the maximum-speed property is missing from the device tree?
> > 
> > When the maximum-speed property is absent, usb_get_maximum_speed() returns
> > USB_SPEED_UNKNOWN, which evaluates to 0. Since 0 is less than USB_SPEED_HIGH,
> > this condition evaluates to true and unconditionally sets usb2only to true.

Right. I missed that.

> > 
> > This appears to override the preceding logic that correctly checked the
> > phy-names property to detect USB 3 capabilities. Could this cause hardware
> > with a USB 3 PHY to be improperly downgraded to USB 2.0 mode?
> 
> Thinh, maybe I should restore the V4 conditional here ?

Sure, but please drop the speed == USB_SPEED_WIRELESS check. This sanity
check is not necessary and would be flagged by dwc3 core if set anyway.

Thanks,
Thinh