From: Alan Stern <stern@rowland.harvard.edu>
To: Eugene Korenevsky <ekorenevsky@astralinux.ru>
Cc: linux-usb@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v5] ehci: fix EHCI host controller initialization sequence
Date: Sun, 10 Jan 2021 11:28:18 -0500 [thread overview]
Message-ID: <20210110162818.GA1161376@rowland.harvard.edu> (raw)
In-Reply-To: <20210110092146.GA12790@himera.home>
On Sun, Jan 10, 2021 at 12:21:47PM +0300, Eugene Korenevsky wrote:
> 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
> Signed-off-by: Eugene Korenevsky <ekorenevsky@astralinux.ru>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
> ---
> 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`
>
> 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
prev parent reply other threads:[~2021-01-10 16:29 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-10 9:21 [PATCH v5] ehci: fix EHCI host controller initialization sequence Eugene Korenevsky
2021-01-10 16:28 ` Alan Stern [this message]
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