linux-kernel - Re: [rfc] exposing MMR's of on-chip peripherals for debugging purposes

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Date:	Mon, 28 Jan 2008 06:06:28 -0500
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	bryan.wu@...log.com
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Bryan Wu" <cooloney.lkml@...il.com>
Subject: Re: [rfc] exposing MMR's of on-chip peripherals for debugging purposes

On Jan 28, 2008 5:40 AM, Bryan Wu <bryan.wu@...log.com> wrote:
> On Mon, 2008-01-28 at 05:16 -0500, Mike Frysinger wrote:
> > the trouble is that this file currently weighs in at ~1.8 megs.  this
> > is because it contains all the information for all Blackfin processors
> > we support (which currently, is about ~23 variants).  it's only going
> > to get bigger as we support more.  Bryan cringes at the thought of
> > submitting it to LKML :).  so i'm fishing around for alternatives ...
> > the code was originally developed against 2.6.21, so UIO was not a
> > possibility.  i'm still not sure if it is ... i'd have to research it
> > a bit more and play with things.
>
> The main reason I am not willing to submit this to mainline is the file
> size. It's almost the biggest file in the kernel source. And it will be
> bigger and bigger when more and more new Blackfin processors supported
> by Linux kernel.

a quick check of current git shows it is significantly larger than any other ;)

> My suggestion is:
> Or more deeper thought:
>  - we don't need all the MMR setup at the same time for debugging. for example, maybe for some developer, he/she only needs one driver MMR for debugging such as watchdog/usb/spi/i2c ....

splitting things up doesnt really address the original issue: there's
a lot of info here to be kept in the kernel

>  - How about split the debug MMR table to each drivers or processors?
>  - watchdog driver implements a debug FS interface for debugging watchdog MMR and other drivers implement their own things.

this had been mentioned before as a possibility but shot down.  you do
not want to tie the creation of these debug files to anything as the
prevents independent development of any other drivers/application that
use the same peripheral.
-mike
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