From: Vlastimil Babka <vbabka.lkml@gmail.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@redhat.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>,
tglx@linutronix.de, peterz@infradead.org,
linux-usb@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v8 2/5] usb: early: add driver for xhci debug capability
Date: Tue, 30 May 2017 15:46:25 +0200 [thread overview]
Message-ID: <d5bbe767-4f80-fe70-dd2c-9b06c3ddda0d@gmail.com> (raw)
In-Reply-To: <1490083293-3792-3-git-send-email-baolu.lu@linux.intel.com>
On 03/21/2017 09:01 AM, Lu Baolu wrote:
> XHCI debug capability (DbC) is an optional but standalone
> functionality provided by an xHCI host controller. Software
> learns this capability by walking through the extended
> capability list of the host. XHCI specification describes
> DbC in the section 7.6.
>
> This patch introduces the code to probe and initialize the
> debug capability hardware during early boot. With hardware
> initialized, the debug target (system on which this code is
> running) will present a debug device through the debug port
> (normally the first USB3 port). The debug device is fully
> compliant with the USB framework and provides the equivalent
> of a very high performance (USB3) full-duplex serial link
> between the debug host and target. The DbC functionality is
> independent of the xHCI host. There isn't any precondition
> from the xHCI host side for the DbC to work.
>
> One use for this feature is kernel debugging, for example
> when your machine crashes very early before the regular
> console code is initialized. Other uses include simpler,
> lockless logging instead of a full-blown printk console
> driver and klogd.
>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
...
> +
> +#define XDBC_TRACE
> +#ifdef XDBC_TRACE
> +#define xdbc_trace trace_printk
Did you forget to remove the #define XDBC_TRACE?
Enabling this driver brings the "trace_printk() being used. Allocating
extra memory. This means that this is a DEBUG kernel and it is unsafe
for production use." message in 4.12-rcX dmesg.
Thanks,
Vlastimil
next prev parent reply other threads:[~2017-05-30 13:46 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-21 8:01 [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Lu Baolu
2017-03-21 8:01 ` [PATCH v8 1/5] x86: add simple udelay calibration Lu Baolu
2017-03-21 12:19 ` [tip:x86/debug] x86/timers: Add " tip-bot for Lu Baolu
2017-05-24 16:56 ` Jan Kiszka
2017-05-25 0:49 ` Lu Baolu
2017-05-02 22:38 ` [PATCH v8 1/5] x86: add " Boris Ostrovsky
2017-05-05 5:41 ` Lu Baolu
2017-05-05 12:50 ` Boris Ostrovsky
2017-07-12 8:02 ` Dou Liyang
2017-07-13 1:17 ` Lu Baolu
2017-07-13 1:39 ` Dou Liyang
2017-07-13 3:00 ` Lu Baolu
2017-07-14 3:21 ` Dou Liyang
2017-03-21 8:01 ` [PATCH v8 2/5] usb: early: add driver for xhci debug capability Lu Baolu
2017-03-21 12:19 ` [tip:x86/debug] usb/early: Add " tip-bot for Lu Baolu
2017-05-30 13:46 ` Vlastimil Babka [this message]
2017-05-31 3:27 ` [PATCH v8 2/5] usb: early: add " Lu Baolu
2017-05-31 6:24 ` Steven Rostedt
2017-06-01 3:35 ` Lu Baolu
2017-05-31 9:38 ` Vlastimil Babka
2017-06-01 3:37 ` Lu Baolu
2017-06-01 8:15 ` Vlastimil Babka
2017-06-01 12:25 ` Peter Zijlstra
2017-06-02 0:47 ` Steven Rostedt
2017-03-21 8:01 ` [PATCH v8 3/5] x86: add support for earlyprintk via USB3 debug port Lu Baolu
2017-03-21 12:20 ` [tip:x86/debug] x86/earlyprintk: Add " tip-bot for Lu Baolu
2017-03-21 8:01 ` [PATCH v8 4/5] usb: serial: add dbc debug device support to usb_debug Lu Baolu
2017-03-21 12:21 ` [tip:x86/debug] usb/serial: Add DBC " tip-bot for Lu Baolu
2017-03-21 8:01 ` [PATCH v8 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu
2017-03-21 12:21 ` [tip:x86/debug] usb/doc: Add " tip-bot for Lu Baolu
2017-03-21 11:33 ` [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Ingo Molnar
2017-03-21 12:27 ` Greg Kroah-Hartman
2017-03-21 12:46 ` Ingo Molnar
2017-03-22 2:23 ` Lu Baolu
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