[PATCH 2/3] usb: xhci-mtk: fix a short packet issue of gen1 isoc-in transfer

[Chunfeng Yun]

For Gen1 isoc-in transfer, host still send out unexpected ACK after device
finish the burst with a short packet, this will cause an exception on the
connected device, such as, a usb 4k camera.
It can be fixed by setting rxfifo depth less than 3, prefer to use 2 here,
the side-effect is that may cause performance drop about 10%, including
bulk transfer.

Fixes: 926d60ae64a6 ("usb: xhci-mtk: modify the SOF/ITP interval for mt8195")
Signed-off-by: Chunfeng Yun <chunfeng.yun at mediatek.com>
---
 drivers/usb/host/xhci-mtk.c | 35 +++++++++++++++++++++++++++++++++--
 drivers/usb/host/xhci-mtk.h |  1 +
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
index bbdf1b0b7be1..a54535877e90 100644
--- a/drivers/usb/host/xhci-mtk.c
+++ b/drivers/usb/host/xhci-mtk.c
@@ -73,6 +73,9 @@
 #define FRMCNT_LEV1_RANG	(0x12b << 8)
 #define FRMCNT_LEV1_RANG_MASK	GENMASK(19, 8)
 
+#define HSCH_CFG1		0x960
+#define SCH3_RXFIFO_DEPTH_MASK	GENMASK(21, 20)
+
 #define SS_GEN2_EOF_CFG		0x990
 #define SSG2EOF_OFFSET		0x3c
 
@@ -165,6 +168,33 @@ static void xhci_mtk_set_frame_interval(struct xhci_hcd_mtk *mtk)
 	writel(value, hcd->regs + SS_GEN2_EOF_CFG);
 }
 
+/*
+ * workaround: usb3.2 gen1 isoc rx hw issue
+ * host send out unexpected ACK afer device fininsh a burst transfer with
+ * a short packet.
+ */
+static void xhci_mtk_rxfifo_depth_set(struct xhci_hcd_mtk *mtk)
+{
+	struct usb_hcd *hcd = mtk->hcd;
+	u32 value;
+
+	if (mtk->rxfifo_depth_quirk) {
+		value = readl(hcd->regs + HSCH_CFG1);
+		value &= ~SCH3_RXFIFO_DEPTH_MASK;
+		value |= FIELD_PREP(SCH3_RXFIFO_DEPTH_MASK, 2);
+		writel(value, hcd->regs + HSCH_CFG1);
+	}
+}
+
+static void xhci_mtk_init_quirk(struct xhci_hcd_mtk *mtk)
+{
+	/* workaround only for mt8195 */
+	xhci_mtk_set_frame_interval(mtk);
+
+	/* workaround for SoCs using SSUSB about before IPM v1.6.0 */
+	xhci_mtk_rxfifo_depth_set(mtk);
+}
+
 static int xhci_mtk_host_enable(struct xhci_hcd_mtk *mtk)
 {
 	struct mu3c_ippc_regs __iomem *ippc = mtk->ippc_regs;
@@ -448,8 +478,7 @@ static int xhci_mtk_setup(struct usb_hcd *hcd)
 		if (ret)
 			return ret;
 
-		/* workaround only for mt8195 */
-		xhci_mtk_set_frame_interval(mtk);
+		xhci_mtk_init_quirk(mtk);
 	}
 
 	ret = xhci_gen_setup(hcd, xhci_mtk_quirks);
@@ -527,6 +556,8 @@ static int xhci_mtk_probe(struct platform_device *pdev)
 	of_property_read_u32(node, "mediatek,u2p-dis-msk",
 			     &mtk->u2p_dis_msk);
 
+	mtk->rxfifo_depth_quirk = of_property_read_bool(node, "mediatek,rxfifo-depth");
+
 	ret = usb_wakeup_of_property_parse(mtk, node);
 	if (ret) {
 		dev_err(dev, "failed to parse uwk property\n");
diff --git a/drivers/usb/host/xhci-mtk.h b/drivers/usb/host/xhci-mtk.h
index 39f7ae7d3087..2443075530e3 100644
--- a/drivers/usb/host/xhci-mtk.h
+++ b/drivers/usb/host/xhci-mtk.h
@@ -166,6 +166,7 @@ struct xhci_hcd_mtk {
 	unsigned int has_ippc:1;
 	unsigned int lpm_support:1;
 	unsigned int u2_lpm_disable:1;
+	unsigned int rxfifo_depth_quirk:1;
 	/* usb remote wakeup */
 	unsigned int uwk_en:1;
 	struct regmap *uwk;
-- 
2.25.1