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

[Roman Vivchar via B4 Relay <devnull+rva333.protonmail.com@kernel.org>]

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