[PATCH v2 0/3] usb: mtu3: add mt6595 support

[PATCH v2 0/3] usb: mtu3: add mt6595 support

[Roman Vivchar via B4 Relay]

This patch series adds mt6595 SoC support to the mtu3 driver.

Unlike the mt8173 and newer controllers, the 6595 uses older IP revision
that can handle only one FIFO slot. Without this series, the current
driver implementation results in 2 to 4 lost bytes on USB transfers.

In mediatek sources, mt6595 is sometimes called 6795. Most of their
clocks/pins are also compatible. It's not clear if 6795 has the same
issue or simply lacks T-PHY patch. Other (rare) mobile SoCs with mtu3,
like mt6757 or 6771, don't need this series.

Another thing worth mentioning, this series is not enough for the USB on
6595. The other T-PHY patch is required to get the link up. This issue
has been observed on some 65xx and most 67xx SoCs. Though this is a
subject for the separate discussion.

Signed-off-by: Roman Vivchar <rva333@protonmail.com>
---
Changes in v2:
- Reword patch 2 commit title
- single_slot -> fifo_single_slot naming
- Drop redundant platform data check
- Link to v1: https://patch.msgid.link/20260917-6595-mtu3-v1-0-a2ba7c230d68@protonmail.com

---
Roman Vivchar (3):
      dt-bindings: usb: mtu3: add mt6595
      usb: mtu3: add SoC platform data for FIFO quirk handling
      usb: mtu3: add mt6595 support

 Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml |  1 +
 drivers/usb/mtu3/mtu3.h                                  |  9 +++++++++
 drivers/usb/mtu3/mtu3_core.c                             |  3 +++
 drivers/usb/mtu3/mtu3_gadget.c                           |  8 ++++++--
 drivers/usb/mtu3/mtu3_plat.c                             | 13 +++++++++++--
 5 files changed, 30 insertions(+), 4 deletions(-)
---
base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
change-id: 20260914-6595-mtu3-82b3048e41ea

Best regards,
--  
Roman Vivchar <rva333@protonmail.com>

[PATCH v2 1/3] dt-bindings: usb: mtu3: add mt6595

[Roman Vivchar via B4 Relay]

From: Roman Vivchar <rva333@protonmail.com>

Add a compatible string for the MTU3 IP found on the MediaTek mt6595 SoC.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Roman Vivchar <rva333@protonmail.com>
---
 Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml
index 21fc6bbe954f..4538df164a16 100644
--- a/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml
+++ b/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml
@@ -22,6 +22,7 @@ properties:
     items:
       - enum:
           - mediatek,mt2712-mtu3
+          - mediatek,mt6595-mtu3
           - mediatek,mt8173-mtu3
           - mediatek,mt8183-mtu3
           - mediatek,mt8186-mtu3

-- 
2.55.0

[PATCH v2 2/3] usb: mtu3: add SoC platform data for FIFO quirk handling

[Roman Vivchar via B4 Relay]

From: Roman Vivchar <rva333@protonmail.com>

Some SoCs, such as mt6595, require specific quirks for the MTU3 to
function properly.

The mt6595 IP block doesn't support multiple slots for the FIFO,
resulting FIFO wrap.

Fix this by adding platform data with a field to handle FIFO limitation.
No functional changes for existing SoCs.

Assisted-by: LLM (debugging)
Signed-off-by: Roman Vivchar <rva333@protonmail.com>
---
 drivers/usb/mtu3/mtu3.h        | 9 +++++++++
 drivers/usb/mtu3/mtu3_core.c   | 3 +++
 drivers/usb/mtu3/mtu3_gadget.c | 8 ++++++--
 drivers/usb/mtu3/mtu3_plat.c   | 8 ++++++--
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/mtu3/mtu3.h b/drivers/usb/mtu3/mtu3.h
index ba5a63669e5f..349e5b20f285 100644
--- a/drivers/usb/mtu3/mtu3.h
+++ b/drivers/usb/mtu3/mtu3.h
@@ -315,6 +315,14 @@ static inline struct ssusb_mtk *dev_to_ssusb(struct device *dev)
 	return dev_get_drvdata(dev);
 }
 
+/**
+ * struct mtu3_platform_data - platform data for the driver.
+ * @fifo_single_slot: the IP can handle only one buffer for bulk transfers
+ */
+struct mtu3_platform_data {
+	bool fifo_single_slot;
+};
+
 /**
  * struct mtu3 - device driver instance data.
  * @slot: MTU3_U2_IP_SLOT_DEFAULT for U2 IP only,
@@ -369,6 +377,7 @@ struct mtu3 {
 	unsigned connected:1;
 	unsigned async_callbacks:1;
 	unsigned separate_fifo:1;
+	unsigned fifo_single_slot:1;
 
 	u8 address;
 	u8 test_mode_nr;
diff --git a/drivers/usb/mtu3/mtu3_core.c b/drivers/usb/mtu3/mtu3_core.c
index 66dbfe1705d5..15f1b80fd0e2 100644
--- a/drivers/usb/mtu3/mtu3_core.c
+++ b/drivers/usb/mtu3/mtu3_core.c
@@ -922,6 +922,7 @@ static int mtu3_set_dma_mask(struct mtu3 *mtu)
 int ssusb_gadget_init(struct ssusb_mtk *ssusb)
 {
 	struct device *dev = ssusb->dev;
+	const struct mtu3_platform_data *pdata = device_get_match_data(dev);
 	struct platform_device *pdev = to_platform_device(dev);
 	struct mtu3 *mtu = NULL;
 	int ret = -ENOMEM;
@@ -930,6 +931,8 @@ int ssusb_gadget_init(struct ssusb_mtk *ssusb)
 	if (mtu == NULL)
 		return -ENOMEM;
 
+	mtu->fifo_single_slot = pdata->fifo_single_slot;
+
 	mtu->irq = platform_get_irq_byname_optional(pdev, "device");
 	if (mtu->irq < 0) {
 		if (mtu->irq == -EPROBE_DEFER)
diff --git a/drivers/usb/mtu3/mtu3_gadget.c b/drivers/usb/mtu3/mtu3_gadget.c
index f224f2ee379a..8ac244d40afd 100644
--- a/drivers/usb/mtu3/mtu3_gadget.c
+++ b/drivers/usb/mtu3/mtu3_gadget.c
@@ -112,8 +112,12 @@ static int mtu3_ep_enable(struct mtu3_ep *mep)
 	mep->ep.desc = desc;
 	mep->ep.comp_desc = comp_desc;
 
-	/* slot mainly affects bulk/isoc transfer, so ignore int */
-	mep->slot = usb_endpoint_xfer_int(desc) ? 0 : mtu->slot;
+	if (mtu->fifo_single_slot)
+		/* older IPs can handle only one slot reliably */
+		mep->slot = 0;
+	else
+		/* slot mainly affects bulk/isoc transfer, so ignore int */
+		mep->slot = usb_endpoint_xfer_int(desc) ? 0 : mtu->slot;
 
 	ret = mtu3_config_ep(mtu, mep, interval, burst, mult);
 	if (ret < 0)
diff --git a/drivers/usb/mtu3/mtu3_plat.c b/drivers/usb/mtu3/mtu3_plat.c
index cc8a864dbd63..bb67da4704b2 100644
--- a/drivers/usb/mtu3/mtu3_plat.c
+++ b/drivers/usb/mtu3/mtu3_plat.c
@@ -611,9 +611,13 @@ static const struct dev_pm_ops mtu3_pm_ops = {
 
 #define DEV_PM_OPS (IS_ENABLED(CONFIG_PM) ? &mtu3_pm_ops : NULL)
 
+static const struct mtu3_platform_data mt8173_platform_data = {
+	.fifo_single_slot = false,
+};
+
 static const struct of_device_id mtu3_of_match[] = {
-	{.compatible = "mediatek,mt8173-mtu3",},
-	{.compatible = "mediatek,mtu3",},
+	{ .compatible = "mediatek,mt8173-mtu3", .data = &mt8173_platform_data },
+	{ .compatible = "mediatek,mtu3", .data = &mt8173_platform_data },
 	{},
 };
 MODULE_DEVICE_TABLE(of, mtu3_of_match);

-- 
2.55.0

[PATCH v2 3/3] usb: mtu3: add mt6595 support

[Roman Vivchar via B4 Relay]

From: Roman Vivchar <rva333@protonmail.com>

Add a platform data for the MediaTek mt6595 SoC MTU3 IP block with a
quirk for single FIFO slot.

Signed-off-by: Roman Vivchar <rva333@protonmail.com>
---
 drivers/usb/mtu3/mtu3_plat.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/mtu3/mtu3_plat.c b/drivers/usb/mtu3/mtu3_plat.c
index bb67da4704b2..9d633695a9be 100644
--- a/drivers/usb/mtu3/mtu3_plat.c
+++ b/drivers/usb/mtu3/mtu3_plat.c
@@ -611,11 +611,16 @@ static const struct dev_pm_ops mtu3_pm_ops = {
 
 #define DEV_PM_OPS (IS_ENABLED(CONFIG_PM) ? &mtu3_pm_ops : NULL)
 
+static const struct mtu3_platform_data mt6595_platform_data = {
+	.fifo_single_slot = true,
+};
+
 static const struct mtu3_platform_data mt8173_platform_data = {
 	.fifo_single_slot = false,
 };
 
 static const struct of_device_id mtu3_of_match[] = {
+	{ .compatible = "mediatek,mt6595-mtu3", .data = &mt6595_platform_data },
 	{ .compatible = "mediatek,mt8173-mtu3", .data = &mt8173_platform_data },
 	{ .compatible = "mediatek,mtu3", .data = &mt8173_platform_data },
 	{},

-- 
2.55.0

Re: [PATCH v2 1/3] dt-bindings: usb: mtu3: add mt6595

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] dt-bindings: usb: mtu3: missing companion xhci compatible for mt6595
--

commit 69c32994e4cd3df8ae84107c2e4552ba6293f82d
Author: Roman Vivchar <rva333@protonmail.com>

dt-bindings: usb: mtu3: add mt6595

Add a compatible string for the MTU3 IP found on the MediaTek mt6595 SoC.

> diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml
> index 21fc6bbe954f9..4538df164a16d 100644
> --- a/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml
> +++ b/Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml
> @@ -22,6 +22,7 @@ properties:
>      items:
>        - enum:
>            - mediatek,mt2712-mtu3
> +          - mediatek,mt6595-mtu3

[Severity: Low]
Does the addition of this compatible string trigger a validation failure
during dtbs_check for mt6595 boards utilizing host or OTG modes?

The mediatek,mtu3.yaml schema enforces that any xHCI child node must comply
with the companion schema:

Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml:
  "^usb@[0-9a-f]+$":
    type: object
    $ref: /schemas/usb/mediatek,mtk-xhci.yaml#

When a device tree for mt6595 configures the MTU3 controller in host or
dual-role mode, it requires a child xHCI node with the mediatek,mt6595-xhci
compatible string.

However, this companion schema is omitted from the patch and does not list
the new compatible string:

Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml:
  compatible:
    items:
      - enum:
          - mediatek,mt2701-xhci
          - mediatek,mt2712-xhci

Should mediatek,mtk-xhci.yaml be updated to include mediatek,mt6595-xhci to
support the mandatory xHCI child node?

>            - mediatek,mt8173-mtu3
>            - mediatek,mt8183-mtu3
>            - mediatek,mt8186-mtu3

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260922-6595-mtu3-v2-0-71203a362b36@protonmail.com?part=1

Re: [PATCH v2 3/3] usb: mtu3: add mt6595 support

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] usb: mtu3: missing NULL check for device_get_match_data result
--

commit d5e4ea09babd67818d32de7a95b82922101210c1
Author: Roman Vivchar <rva333@protonmail.com>

usb: mtu3: add mt6595 support

This commit adds platform data for the MediaTek mt6595 SoC to the MTU3 USB
driver. It introduces a quirk to enable single FIFO slot mode for this
specific platform.

> diff --git a/drivers/usb/mtu3/mtu3_plat.c b/drivers/usb/mtu3/mtu3_plat.c
> index bb67da4704b29..9d633695a9bed 100644
> --- a/drivers/usb/mtu3/mtu3_plat.c
> +++ b/drivers/usb/mtu3/mtu3_plat.c
> @@ -611,11 +611,16 @@ static const struct dev_pm_ops mtu3_pm_ops = {
>  
>  #define DEV_PM_OPS (IS_ENABLED(CONFIG_PM) ? &mtu3_pm_ops : NULL)
>  
> +static const struct mtu3_platform_data mt6595_platform_data = {
> +	.fifo_single_slot = true,
> +};
> +
>  static const struct mtu3_platform_data mt8173_platform_data = {
>  	.fifo_single_slot = false,
>  };
>  
>  static const struct of_device_id mtu3_of_match[] = {
> +	{ .compatible = "mediatek,mt6595-mtu3", .data = &mt6595_platform_data },

[Severity: High]
Does this code allow an unprotected dereference of pdata if matched without
OF data?

The mtu3 platform driver allows matching by name (via .driver.name = "mtu3"),
in which case device_get_match_data() returns NULL because there is no
corresponding id_table with driver_data.

The mtu3_probe() function gracefully tolerates a missing of_node, allowing
execution to reach ssusb_gadget_init(), where pdata->fifo_single_slot is
unconditionally dereferenced:

drivers/usb/mtu3/mtu3_core.c:ssusb_gadget_init() {
    ...
    mtu->fifo_single_slot = pdata->fifo_single_slot;
    ...
}

While typically bound via device tree, manual binding via sysfs or missing
.data in future OF match entries will trigger a kernel panic (Oops) here.

>  	{ .compatible = "mediatek,mt8173-mtu3", .data = &mt8173_platform_data },
>  	{ .compatible = "mediatek,mtu3", .data = &mt8173_platform_data },
>  	{},
>  };

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260922-6595-mtu3-v2-0-71203a362b36@protonmail.com?part=3

Re: [PATCH v2 2/3] usb: mtu3: add SoC platform data for FIFO quirk handling

[AngeloGioacchino Del Regno]

On 9/22/26 12:36, Roman Vivchar via B4 Relay wrote:
> From: Roman Vivchar <rva333@protonmail.com>
> 
> Some SoCs, such as mt6595, require specific quirks for the MTU3 to
> function properly.
> 
> The mt6595 IP block doesn't support multiple slots for the FIFO,
> resulting FIFO wrap.
> 
> Fix this by adding platform data with a field to handle FIFO limitation.
> No functional changes for existing SoCs.
> 
> Assisted-by: LLM (debugging)
> Signed-off-by: Roman Vivchar <rva333@protonmail.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Re: [PATCH v2 3/3] usb: mtu3: add mt6595 support

[AngeloGioacchino Del Regno]

On 9/22/26 12:36, Roman Vivchar via B4 Relay wrote:
> From: Roman Vivchar <rva333@protonmail.com>
> 
> Add a platform data for the MediaTek mt6595 SoC MTU3 IP block with a
> quirk for single FIFO slot.
> 
> Signed-off-by: Roman Vivchar <rva333@protonmail.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Re: [PATCH v2 1/3] dt-bindings: usb: mtu3: add mt6595

[Krzysztof Kozlowski]

On Tue, Sep 22, 2026 at 01:36:40PM +0300, Roman Vivchar wrote:
> Add a compatible string for the MTU3 IP found on the MediaTek mt6595 SoC.
> 
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> Signed-off-by: Roman Vivchar <rva333@protonmail.com>
> ---
>  Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml | 1 +
>  1 file changed, 1 insertion(+)

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof