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Subject[PATCH v6] 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 <stern@rowland.harvard.edu>
Signed-off-by: Eugene Korenevsky <ekorenevsky@astralinux.ru>
---
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 <stern@rowland.harvard.edu>` tag

drivers/usb/host/ehci-hcd.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index e358ae17d51e..1926b328b6aa 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -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));
--
2.20.1
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