From: Ingo Molnar <mingo@kernel.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mathias Nyman <mathias.nyman@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
tglx@linutronix.de, peterz@infradead.org,
linux-usb@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability
Date: Sun, 22 Jan 2017 10:04:23 +0100 [thread overview]
Message-ID: <20170122090423.GA15061@gmail.com> (raw)
In-Reply-To: <58817A25.6080305@linux.intel.com>
* Lu Baolu <baolu.lu@linux.intel.com> wrote:
> >
> >> +static void xdbc_runtime_delay(unsigned long count)
> >> +{
> >> + udelay(count);
> >> +}
> >> +static void (*xdbc_delay)(unsigned long) = xdbc_early_delay;
> > Is this udelay() complication really necessary? udelay() should work fine even in
> > early code. It might not be precisely calibrated, but should be good enough.
>
> I tried udelay() in the early code. It's not precise enough for the
> hardware handshaking.
Possibly because on x86 early udelay() did not work at all - i.e. there's no delay
whatsoever.
Could you try it on top of this commit in tip:timers/core:
4c45c5167c95 x86/timer: Make delay() work during early bootup
?
Thanks,
Ingo
next prev parent reply other threads:[~2017-01-22 9:04 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-15 6:02 [PATCH v5 0/4] usb: early: add support for early printk through USB3 debug port Lu Baolu
2016-11-15 6:02 ` [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu
2017-01-19 9:37 ` Ingo Molnar
2017-01-20 2:47 ` Lu Baolu
2017-01-22 9:04 ` Ingo Molnar [this message]
2017-01-24 4:44 ` Lu Baolu
2017-01-24 8:20 ` Ingo Molnar
2017-01-25 5:28 ` Lu Baolu
2017-01-25 9:23 ` Ingo Molnar
2017-01-25 9:57 ` Peter Zijlstra
2017-01-25 12:27 ` Lu Baolu
2017-01-25 14:38 ` Peter Zijlstra
2017-01-25 15:51 ` Lu Baolu
2017-01-25 16:16 ` Peter Zijlstra
2017-01-26 3:37 ` Lu Baolu
2017-01-26 7:19 ` Ingo Molnar
2017-01-26 7:49 ` Lu Baolu
2017-01-26 8:17 ` Ingo Molnar
2017-01-26 10:28 ` Peter Zijlstra
2017-01-26 16:01 ` Ingo Molnar
2017-01-26 17:39 ` Peter Zijlstra
2017-01-27 6:51 ` Ingo Molnar
2017-02-09 5:59 ` Lu Baolu
2017-01-26 7:22 ` Ingo Molnar
2017-02-09 7:37 ` Lu Baolu
2017-01-25 12:17 ` Lu Baolu
2017-01-26 3:26 ` Lu Baolu
2016-11-15 6:02 ` [PATCH v5 2/4] x86: add support for earlyprintk via USB3 debug port Lu Baolu
2017-01-19 9:38 ` Ingo Molnar
2017-01-20 2:48 ` Lu Baolu
2016-11-15 6:02 ` [PATCH v5 3/4] usb: serial: usb_debug: add support for dbc debug device Lu Baolu
2017-01-19 9:39 ` Ingo Molnar
2017-01-20 2:50 ` Lu Baolu
2016-11-15 6:02 ` [PATCH v5 4/4] usb: doc: add document for USB3 debug port usage Lu Baolu
2017-01-19 9:41 ` Ingo Molnar
2017-01-20 2:53 ` Lu Baolu
2017-01-18 6:20 ` [PATCH v5 0/4] usb: early: add support for early printk through USB3 debug port Lu Baolu
2017-01-19 9:06 ` Greg Kroah-Hartman
2017-01-19 9:09 ` Ingo Molnar
2017-01-19 11:24 ` Mathias Nyman
2017-01-19 9:12 ` Ingo Molnar
2017-01-20 2:56 ` Lu Baolu
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