From mboxrd@z Thu Jan  1 00:00:00 1970
From: olof@lixom.net (Olof Johansson)
Date: Tue, 15 Jan 2013 11:04:01 -0800
Subject: [PATCH 4/4] ARM: uncompress: support uncompress debug for
 multiplatform build
In-Reply-To: <20130112032934.GA14865@S2101-09.ap.freescale.net>
References: <1355319945-3199-1-git-send-email-shawn.guo@linaro.org>
 <1355319945-3199-5-git-send-email-shawn.guo@linaro.org>
 <20130111191116.GA999@quad.lixom.net>
 <20130112032934.GA14865@S2101-09.ap.freescale.net>
Message-ID: <20130115190401.GA28333@quad.lixom.net>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Sat, Jan 12, 2013 at 11:29:37AM +0800, Shawn Guo wrote:
> On Fri, Jan 11, 2013 at 11:11:16AM -0800, Olof Johansson wrote:
> > Hi,
> > 
> > On Wed, Dec 12, 2012 at 09:45:45PM +0800, Shawn Guo wrote:
> > > When moving to multiplatform build, platforms lose the output from
> > > decompressor.  Not only does it mean that we will never see message
> > > "Uncompressing Linux... done, booting the kernel.", but also that
> > > the debug facility in arch/arm/boot/compressed/head.S outputs nothing
> > > even DEBUG is turned on.
> > > 
> > > The patch follows the approach handling DEBUG_LL to create a Kconfig
> > > symbol CONFIG_UNCOMPRESS_INCLUDE for choosing the correct uncompress
> > > header.  For traditional build, mach/uncompress.h will be included in
> > > arch/arm/boot/compressed/misc.c.  For multiplatform build with none
> > > DEBUG_LL port enabled, debug/uncompress/dummy.h will be used.  And
> > > for multiplatform build with a DEBUG_LL port, platform specific
> > > uncompress header like debug/uncompress/imx.h will come to play.
> > > 
> > > Different from traditional build that uncompress output and DEBUG_LL
> > > are two separated pieces, for multiplatform build uncompress output
> > > becomes a subset of DEBUG_LL and will not work unless DEBUG_LL is
> > > enabled.
> > > 
> > > The arch/arm/include/debug/uncompress/imx.h is cleaned up and added
> > > here as an example to show how this approach works.
> > 
> > Since this requires you to define a debug uart to get uncompress output,
> > it would make more sense to do a generic wrapper that uses the debug
> > code generically, instead of having to add this kind of wrapper for
> > every platform. That would solve it for all of them at once.
> > 
> I'm not entirely sure about what you mean here.  Can you please
> elaborate that generic wrapper in your mind a little bit?

Hi,

Sorry for the delay in responding.

Most functionality to deal with this already exist in the
include/debug/*.S files files, you just need to instantiate the macros
somewhere (compressed/head.S, or a separate file), and wrap the calls
to those instantiated assembly functions in a generic header file.

That way, every platform that has a DEBUG_LL implementation should be able to
reuse that, and no need to enable every platform one by one.

Or am I missing some complexity involved here?


-Olof