From: Eugene Korenevsky <ekorenevsky@astralinux.ru>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v3] ehci: fix EHCI host controller initialization sequence
Date: Sun, 10 Jan 2021 10:37:37 +0300 [thread overview]
Message-ID: <20210110073737.GA10541@himera.home> (raw)
In-Reply-To: <20210109210452.GA1136657@rowland.harvard.edu>
> > - ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */
> You should not remove the ehci_readl call above. With that line gone,
> the PCI bus might not send the new value of configured_flag to the
> controller until after the 5-ms sleep has ended, which makes the msleep
> useless.
Could not find reads from USBCMD in similar drivers (for
example here: https://github.com/NetBSD/src/blob/trunk/sys/dev/usb/ehci.c#L625).
Is this feature (reading from USBCMD for unblocking posted writes)
documented anywhere or it is found empirically?
--
Eugene
next prev parent reply other threads:[~2021-01-10 7:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-09 18:18 [PATCH v3] ehci: fix EHCI host controller initialization sequence Eugene Korenevsky
2021-01-09 21:04 ` Alan Stern
2021-01-10 7:37 ` Eugene Korenevsky [this message]
2021-01-10 16:44 ` Alan Stern
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