[PATCH v3 0/2] Support for Samsung Exynos 7870 DW-USB device in controller

[PATCH v3 0/2] Support for Samsung Exynos 7870 DW-USB device in controller

[Kaustabh Chakraborty]

This patch series aims to add support for the Samsung Exynos 7870 DW-USB
controller. The support is added in the dwc3-generic driver.

This also has a patch which allows the driver to fall back to "otg"
dual-role mode when none is specified in devicetree.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
---
Changes in v3:
- change link in [v2 1/2] to upstream repository (Marek Vasut)
- use dev_info() instead of pr_info() (Marek Vasut)
- Link to v2: https://lore.kernel.org/r/20260103-usb-dwc3-exynos7870-v2-0-67441680d287@disroot.org

Changes in v2:
- clarify rationale behind [v1 1/2] (Marek Vasut)
- Link to v1: https://lore.kernel.org/r/20251017-usb-dwc3-exynos7870-v1-0-fe46e2ed1908@disroot.org

---
Kaustabh Chakraborty (2):
      usb: dwc3-generic: allow fallback of dr_mode property to "otg"
      usb: dwc3-generic: add support for exynos7870

 drivers/usb/dwc3/dwc3-generic.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
---
base-commit: 5e7624979083e2bc163e18165452d8ead462b58c
change-id: 20251014-usb-dwc3-exynos7870-5d38b538a06e

Best regards,
-- 
Kaustabh Chakraborty <kauschluss@disroot.org>

[PATCH v3 1/2] usb: dwc3-generic: allow fallback of dr_mode property to "otg"

[Kaustabh Chakraborty]

Documentation [1] states that the default value of the dr_mode property
is "otg". It also isn't marked a mandatory node, so it may or may not be
set. So, accordingly if dr_mode is not mentioned in the devicetree node,
OTG mode must be assumed.

In this driver however, this case is not handled. If dr_mode is not
mentioned, USB_DR_MODE_UNKNOWN is set. The logic implemented raises an
error, instead of falling back to USB_DR_MODE_OTG. Correct this to
conform to the specification.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/tree/Bindings/usb/usb-drd.yaml?h=v6.18-dts [1]
Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
---
 drivers/usb/dwc3/dwc3-generic.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
index c09014aec60..c15eda19e8f 100644
--- a/drivers/usb/dwc3/dwc3-generic.c
+++ b/drivers/usb/dwc3/dwc3-generic.c
@@ -10,6 +10,7 @@
 #include <dm.h>
 #include <reset.h>
 #include <asm/gpio.h>
+#include <dm/device_compat.h>
 #include <dm/lists.h>
 #include <linux/delay.h>
 #include <linux/usb/gadget.h>
@@ -173,8 +174,8 @@ static int dwc3_generic_of_to_plat(struct udevice *dev)
 		node = dev_ofnode(dev->parent);
 		plat->dr_mode = usb_get_dr_mode(node);
 		if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
-			pr_err("Invalid usb mode setup\n");
-			return -ENODEV;
+			dev_info(dev, "No USB mode specified. Using 'otg'\n");
+			plat->dr_mode = USB_DR_MODE_OTG;
 		}
 	}
 
@@ -516,6 +517,10 @@ static int dwc3_glue_bind_common(struct udevice *parent, ofnode node)
 	if (!dr_mode)
 		dr_mode = usb_get_dr_mode(node);
 
+	/* usb mode must fallback to peripheral if not known */
+	if (dr_mode == USB_DR_MODE_UNKNOWN)
+		dr_mode = USB_DR_MODE_OTG;
+
 	if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
 	    (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
 		debug("%s: dr_mode: OTG or Peripheral\n", __func__);

-- 
2.52.0

Re: [PATCH v3 1/2] usb: dwc3-generic: allow fallback of dr_mode property to "otg"

[Mattijs Korpershoek]

Hi Kaustabh,

Thank you for the patch.

On Thu, Jan 08, 2026 at 18:03, Kaustabh Chakraborty <kauschluss@disroot.org> wrote:

> Documentation [1] states that the default value of the dr_mode property
> is "otg". It also isn't marked a mandatory node, so it may or may not be
> set. So, accordingly if dr_mode is not mentioned in the devicetree node,
> OTG mode must be assumed.
>
> In this driver however, this case is not handled. If dr_mode is not
> mentioned, USB_DR_MODE_UNKNOWN is set. The logic implemented raises an
> error, instead of falling back to USB_DR_MODE_OTG. Correct this to
> conform to the specification.
>
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/tree/Bindings/usb/usb-drd.yaml?h=v6.18-dts [1]
> Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>

Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

Note: there is a similar patch submitted by Casey here:
https://lore.kernel.org/all/20260114-casey-usb-role-switch-v1-1-fb7a626466b9@linaro.org/

Can you have a look at that one please? You could review it or test it
to see if it works for you?

Thanks!
Mattijs

> ---
>  drivers/usb/dwc3/dwc3-generic.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
> index c09014aec60..c15eda19e8f 100644
> --- a/drivers/usb/dwc3/dwc3-generic.c
> +++ b/drivers/usb/dwc3/dwc3-generic.c
> @@ -10,6 +10,7 @@
>  #include <dm.h>
>  #include <reset.h>
>  #include <asm/gpio.h>
> +#include <dm/device_compat.h>
>  #include <dm/lists.h>
>  #include <linux/delay.h>
>  #include <linux/usb/gadget.h>
> @@ -173,8 +174,8 @@ static int dwc3_generic_of_to_plat(struct udevice *dev)
>  		node = dev_ofnode(dev->parent);
>  		plat->dr_mode = usb_get_dr_mode(node);
>  		if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
> -			pr_err("Invalid usb mode setup\n");
> -			return -ENODEV;
> +			dev_info(dev, "No USB mode specified. Using 'otg'\n");
> +			plat->dr_mode = USB_DR_MODE_OTG;
>  		}
>  	}
>  
> @@ -516,6 +517,10 @@ static int dwc3_glue_bind_common(struct udevice *parent, ofnode node)
>  	if (!dr_mode)
>  		dr_mode = usb_get_dr_mode(node);
>  
> +	/* usb mode must fallback to peripheral if not known */
> +	if (dr_mode == USB_DR_MODE_UNKNOWN)
> +		dr_mode = USB_DR_MODE_OTG;
> +
>  	if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
>  	    (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
>  		debug("%s: dr_mode: OTG or Peripheral\n", __func__);
>
> -- 
> 2.52.0

Re: [PATCH v3 1/2] usb: dwc3-generic: allow fallback of dr_mode property to "otg"

[Kaustabh Chakraborty]

On 2026-01-16 13:33 +01:00, Mattijs Korpershoek wrote:
> Hi Kaustabh,
>
> Thank you for the patch.
>
> On Thu, Jan 08, 2026 at 18:03, Kaustabh Chakraborty <kauschluss@disroot.org> wrote:
>
>> Documentation [1] states that the default value of the dr_mode property
>> is "otg". It also isn't marked a mandatory node, so it may or may not be
>> set. So, accordingly if dr_mode is not mentioned in the devicetree node,
>> OTG mode must be assumed.
>>
>> In this driver however, this case is not handled. If dr_mode is not
>> mentioned, USB_DR_MODE_UNKNOWN is set. The logic implemented raises an
>> error, instead of falling back to USB_DR_MODE_OTG. Correct this to
>> conform to the specification.
>>
>> Link: https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/tree/Bindings/usb/usb-drd.yaml?h=v6.18-dts [1]
>> Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>
> Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

Thanks for your insight, but isn't this patch applied? This has been
merged into u-boot/master already. But I don't see it in next.
Confusing.

>
> Note: there is a similar patch submitted by Casey here:
> https://lore.kernel.org/all/20260114-casey-usb-role-switch-v1-1-fb7a626466b9@linaro.org/
>
> Can you have a look at that one please? You could review it or test it
> to see if it works for you?

This patch addresses a single point of failure, unlike mine.

>
> Thanks!
> Mattijs
>
>> ---
>>  drivers/usb/dwc3/dwc3-generic.c | 9 +++++++--
>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
>> index c09014aec60..c15eda19e8f 100644
>> --- a/drivers/usb/dwc3/dwc3-generic.c
>> +++ b/drivers/usb/dwc3/dwc3-generic.c
>> @@ -10,6 +10,7 @@
>>  #include <dm.h>
>>  #include <reset.h>
>>  #include <asm/gpio.h>
>> +#include <dm/device_compat.h>
>>  #include <dm/lists.h>
>>  #include <linux/delay.h>
>>  #include <linux/usb/gadget.h>
>> @@ -173,8 +174,8 @@ static int dwc3_generic_of_to_plat(struct udevice *dev)
>>  		node = dev_ofnode(dev->parent);
>>  		plat->dr_mode = usb_get_dr_mode(node);
>>  		if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
>> -			pr_err("Invalid usb mode setup\n");
>> -			return -ENODEV;
>> +			dev_info(dev, "No USB mode specified. Using 'otg'\n");
>> +			plat->dr_mode = USB_DR_MODE_OTG;
>>  		}
>>  	}
>>  
>> @@ -516,6 +517,10 @@ static int dwc3_glue_bind_common(struct udevice *parent, ofnode node)
>>  	if (!dr_mode)
>>  		dr_mode = usb_get_dr_mode(node);
>>  
>> +	/* usb mode must fallback to peripheral if not known */
>> +	if (dr_mode == USB_DR_MODE_UNKNOWN)
>> +		dr_mode = USB_DR_MODE_OTG;
>> +
>>  	if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
>>  	    (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
>>  		debug("%s: dr_mode: OTG or Peripheral\n", __func__);
>>
>> -- 
>> 2.52.0

Re: [PATCH v3 1/2] usb: dwc3-generic: allow fallback of dr_mode property to "otg"

[Mattijs Korpershoek]

On Fri, Jan 16, 2026 at 19:12, "Kaustabh Chakraborty" <kauschluss@disroot.org> wrote:

> On 2026-01-16 13:33 +01:00, Mattijs Korpershoek wrote:
>> Hi Kaustabh,
>>
>> Thank you for the patch.
>>
>> On Thu, Jan 08, 2026 at 18:03, Kaustabh Chakraborty <kauschluss@disroot.org> wrote:
>>
>>> Documentation [1] states that the default value of the dr_mode property
>>> is "otg". It also isn't marked a mandatory node, so it may or may not be
>>> set. So, accordingly if dr_mode is not mentioned in the devicetree node,
>>> OTG mode must be assumed.
>>>
>>> In this driver however, this case is not handled. If dr_mode is not
>>> mentioned, USB_DR_MODE_UNKNOWN is set. The logic implemented raises an
>>> error, instead of falling back to USB_DR_MODE_OTG. Correct this to
>>> conform to the specification.
>>>
>>> Link: https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/tree/Bindings/usb/usb-drd.yaml?h=v6.18-dts [1]
>>> Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
>>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>>
>> Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
>
> Thanks for your insight, but isn't this patch applied? This has been
> merged into u-boot/master already. But I don't see it in next.
> Confusing.

You are right. This patch was already applied. I usually check for an
email that states that the patch was applied but I forgot Marek usually
does not send those.
Sorry about that, I generated un-necessary noise.

It's normal that your patch has only be applied into u-boot/master.

Right now, we are in the U-Boot merge window. During this time, the next
branch is closed. All development and fixes go into master directly.

See:
https://docs.u-boot.org/en/latest/develop/release_cycle.html#current-status
https://docs.u-boot.org/en/latest/develop/process.html#management-summary

Hope that clears out the confusion.

>
>>
>> Note: there is a similar patch submitted by Casey here:
>> https://lore.kernel.org/all/20260114-casey-usb-role-switch-v1-1-fb7a626466b9@linaro.org/
>>
>> Can you have a look at that one please? You could review it or test it
>> to see if it works for you?
>
> This patch addresses a single point of failure, unlike mine.
>
>>
>> Thanks!
>> Mattijs
>>
>>> ---
>>>  drivers/usb/dwc3/dwc3-generic.c | 9 +++++++--
>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
>>> index c09014aec60..c15eda19e8f 100644
>>> --- a/drivers/usb/dwc3/dwc3-generic.c
>>> +++ b/drivers/usb/dwc3/dwc3-generic.c
>>> @@ -10,6 +10,7 @@
>>>  #include <dm.h>
>>>  #include <reset.h>
>>>  #include <asm/gpio.h>
>>> +#include <dm/device_compat.h>
>>>  #include <dm/lists.h>
>>>  #include <linux/delay.h>
>>>  #include <linux/usb/gadget.h>
>>> @@ -173,8 +174,8 @@ static int dwc3_generic_of_to_plat(struct udevice *dev)
>>>  		node = dev_ofnode(dev->parent);
>>>  		plat->dr_mode = usb_get_dr_mode(node);
>>>  		if (plat->dr_mode == USB_DR_MODE_UNKNOWN) {
>>> -			pr_err("Invalid usb mode setup\n");
>>> -			return -ENODEV;
>>> +			dev_info(dev, "No USB mode specified. Using 'otg'\n");
>>> +			plat->dr_mode = USB_DR_MODE_OTG;
>>>  		}
>>>  	}
>>>  
>>> @@ -516,6 +517,10 @@ static int dwc3_glue_bind_common(struct udevice *parent, ofnode node)
>>>  	if (!dr_mode)
>>>  		dr_mode = usb_get_dr_mode(node);
>>>  
>>> +	/* usb mode must fallback to peripheral if not known */
>>> +	if (dr_mode == USB_DR_MODE_UNKNOWN)
>>> +		dr_mode = USB_DR_MODE_OTG;
>>> +
>>>  	if (CONFIG_IS_ENABLED(DM_USB_GADGET) &&
>>>  	    (dr_mode == USB_DR_MODE_PERIPHERAL || dr_mode == USB_DR_MODE_OTG)) {
>>>  		debug("%s: dr_mode: OTG or Peripheral\n", __func__);
>>>
>>> -- 
>>> 2.52.0

[PATCH v3 2/2] usb: dwc3-generic: add support for exynos7870

[Kaustabh Chakraborty]

Exynos7870's DWC3 glue layer is quite simple, consisting of a few
clocks, which is handled by this driver. Add the compatible string in
here.

Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
---
 drivers/usb/dwc3/dwc3-generic.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc3/dwc3-generic.c b/drivers/usb/dwc3/dwc3-generic.c
index c15eda19e8f..bb11613a587 100644
--- a/drivers/usb/dwc3/dwc3-generic.c
+++ b/drivers/usb/dwc3/dwc3-generic.c
@@ -711,6 +711,7 @@ static const struct udevice_id dwc3_glue_ids[] = {
 	{ .compatible = "fsl,imx8mp-dwc3", .data = (ulong)&imx8mp_ops },
 	{ .compatible = "fsl,imx8mq-dwc3" },
 	{ .compatible = "intel,tangier-dwc3" },
+	{ .compatible = "samsung,exynos7870-dwusb3" },
 	{ .compatible = "samsung,exynos850-dwusb3" },
 	{ }
 };

-- 
2.52.0

Re: [PATCH v3 2/2] usb: dwc3-generic: add support for exynos7870

[Mattijs Korpershoek]

Hi Kaustabh,

Thank you for the patch.

On Thu, Jan 08, 2026 at 18:03, Kaustabh Chakraborty <kauschluss@disroot.org> wrote:

> Exynos7870's DWC3 glue layer is quite simple, consisting of a few
> clocks, which is handled by this driver. Add the compatible string in
> here.
>
> Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>

Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

> ---
>  drivers/usb/dwc3/dwc3-generic.c | 1 +
>  1 file changed, 1 insertion(+)
>