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ehci: fix EHCI host controller initialization sequence

PATCH New Eugene Korenevsky 1 participant 1 message Jan 10, 2021

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USB USB ehci driver
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Eugene Korenevsky

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PATCH v6 1/1 ehci: fix EHCI host controller initialization sequence

According to EHCI spec, EHCI HC clears USBSTS.HCHalted whenever USBCMD.RS=1.

However, it is a good practice to wait some time after setting USBCMD.RS (approximately 100ms) until USBSTS.HCHalted become zero.

Without this waiting, VirtualBox's EHCI virtual HC accidentally hangs (see BugLink).

BugLink https://bugzilla.kernel.org/show_bug.cgi?id=211095
Acked-by Alan Stern <[email protected]>
Signed-off-by Eugene Korenevsky <[email protected]>

---
v1: initial patch
v2: add BugLink tag
v3: add Revieved-By tags (incorrect), restore msleep(5)
v4: remove Reviewed-By tags, restore reading from USBCMD prior to msleep, adjust description
v5: add patch changelog
v6: add Acked-by: Alan Stern <[email protected]> tag

 drivers/usb/host/ehci-hcd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
drivers/usb/host/ehci-hcd.c +12 -0
index e358ae17d51e..1926b328b6aa 100644
@@ -574,6 +574,7 @@ static int ehci_run (struct usb_hcd *hcd)
 	struct ehci_hcd		*ehci = hcd_to_ehci (hcd);
 	u32			temp;
 	u32			hcc_params;
+	int			rc;
 
 	hcd->uses_new_polling = 1;
 

@@ -629,9 +630,20 @@ static int ehci_run (struct usb_hcd *hcd)
 	down_write(&ehci_cf_port_reset_rwsem);
 	ehci->rh_state = EHCI_RH_RUNNING;
 	ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag);
+
+	/* Wait until HC become operational */
 	ehci_readl(ehci, &ehci->regs->command);	/* unblock posted writes */
 	msleep(5);
+	rc = ehci_handshake(ehci, &ehci->regs->status, STS_HALT, 0, 100 * 1000);
+
 	up_write(&ehci_cf_port_reset_rwsem);
+
+	if (rc) {
+		ehci_err(ehci, "USB %x.%x, controller refused to start: %d\n",
+			 ((ehci->sbrn & 0xf0)>>4), (ehci->sbrn & 0x0f), rc);
+		return rc;
+	}
+
 	ehci->last_periodic_enable = ktime_get_real();
 
 	temp = HC_VERSION(ehci, ehci_readl(ehci, &ehci->caps->hc_capbase));
Signature · 1 line
2.20.1