[PATCH 2/2] usb: dwc3: Add workaround for host mode VBUS glitch when boot

[Frank Li <Frank.Li@nxp.com>]

From: Ran Wang <ran.wang_1@nxp.com>

When DWC3 is set to host mode by programming register DWC3_GCTL, VBUS
(or its control signal) will be turned on immediately on related Root Hub
ports. Then, the VBUS is turned off for a little while(15us) when do xhci
reset (conducted by xhci driver) and back to normal finally, we can
observe a negative glitch of related signal happen.

This VBUS glitch might cause some USB devices enumeration fail if kernel
boot with them connected. Such as LS1012AFWRY/LS1043ARDB/LX2160AQDS
/LS1088ARDB with Kingston 16GB USB2.0/Kingston USB3.0/JetFlash Transcend
4GB USB2.0 drives. The fail cases include enumerated as full-speed device
or report wrong device descriptor, etc.

One SW workaround which can fix this is by programing all xhci PORTSC[PP]
to 0 to turn off VBUS immediately after setting host mode in DWC3 driver
(per signal measurement result, it will be too late to do it in
xhci-plat.c or xhci.c). Then, after xhci reset complete in xhci driver,
PORTSC[PP]s' value will back to 1 automatically and VBUS on at that time,
no glitch happen and normal enumeration process has no impact.

Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---

Notes:
    Last review at June 06, 2019. Fixed all review comments and sent again.
    
    https://lore.kernel.org/linux-kernel/AM5PR0402MB2865979E26017BC5937DBBA5F1170@AM5PR0402MB2865.eurprd04.prod.outlook.com/

 drivers/usb/dwc3/core.c |  2 ++
 drivers/usb/dwc3/core.h |  2 ++
 drivers/usb/dwc3/host.c | 46 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 3e55838c00014..a57adf0c11dd1 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1626,6 +1626,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	dwc->dis_split_quirk = device_property_read_bool(dev,
 				"snps,dis-split-quirk");
 
+	dwc->host_vbus_glitches = device_property_read_bool(dev, "snps,host-vbus-glitches");
+
 	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
 	dwc->tx_de_emphasis = tx_de_emphasis;
 
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index e3eea965e57bf..0269bacbbf6bd 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1135,6 +1135,7 @@ struct dwc3_scratchpad_array {
  * @dis_split_quirk: set to disable split boundary.
  * @wakeup_configured: set if the device is configured for remote wakeup.
  * @suspended: set to track suspend event due to U3/L2.
+ * @host_vbus_glitches: set to avoid vbus glitch during xhci reset.
  * @imod_interval: set the interrupt moderation interval in 250ns
  *			increments or 0 to disable.
  * @max_cfg_eps: current max number of IN eps used across all USB configs.
@@ -1353,6 +1354,7 @@ struct dwc3 {
 	unsigned		tx_de_emphasis:2;
 
 	unsigned		dis_metastability_quirk:1;
+	unsigned		host_vbus_glitches:1;
 
 	unsigned		dis_split_quirk:1;
 	unsigned		async_callbacks:1;
diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
index 61f57fe5bb783..af8903ee37c20 100644
--- a/drivers/usb/dwc3/host.c
+++ b/drivers/usb/dwc3/host.c
@@ -11,6 +11,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 
+#include "../host/xhci.h"
 #include "core.h"
 
 static void dwc3_host_fill_xhci_irq_res(struct dwc3 *dwc,
@@ -28,6 +29,44 @@ static void dwc3_host_fill_xhci_irq_res(struct dwc3 *dwc,
 		dwc->xhci_resources[1].name = name;
 }
 
+#define XHCI_HCSPARAMS1		0x4
+#define XHCI_PORTSC_BASE	0x400
+
+/*
+ * dwc3_power_off_all_roothub_ports - Power off all Root hub ports
+ * @dwc3: Pointer to our controller context structure
+ */
+static void dwc3_power_off_all_roothub_ports(struct dwc3 *dwc)
+{
+	int i, port_num;
+	u32 reg, op_regs_base, offset;
+	void __iomem *xhci_regs;
+
+	/* xhci regs is not mapped yet, do it temperary here */
+	if (dwc->xhci_resources[0].start) {
+		xhci_regs = ioremap(dwc->xhci_resources[0].start,
+				DWC3_XHCI_REGS_END);
+		if (IS_ERR(xhci_regs)) {
+			dev_err(dwc->dev, "Failed to ioremap xhci_regs\n");
+			return;
+		}
+
+		op_regs_base = HC_LENGTH(readl(xhci_regs));
+		reg = readl(xhci_regs + XHCI_HCSPARAMS1);
+		port_num = HCS_MAX_PORTS(reg);
+
+		for (i = 1; i <= port_num; i++) {
+			offset = op_regs_base + XHCI_PORTSC_BASE + 0x10*(i-1);
+			reg = readl(xhci_regs + offset);
+			reg &= ~PORT_POWER;
+			writel(reg, xhci_regs + offset);
+		}
+
+		iounmap(xhci_regs);
+	} else
+		dev_err(dwc->dev, "xhci base reg invalid\n");
+}
+
 static int dwc3_host_get_irq(struct dwc3 *dwc)
 {
 	struct platform_device	*dwc3_pdev = to_platform_device(dwc->dev);
@@ -66,6 +105,13 @@ int dwc3_host_init(struct dwc3 *dwc)
 	int			ret, irq;
 	int			prop_idx = 0;
 
+	/*
+	 * We have to power off all Root hub ports immediately after DWC3 set
+	 * to host mode to avoid VBUS glitch happen when xhci get reset later.
+	 */
+	if (dwc->host_vbus_glitches)
+		dwc3_power_off_all_roothub_ports(dwc);
+
 	irq = dwc3_host_get_irq(dwc);
 	if (irq < 0)
 		return irq;
-- 
2.34.1