From mboxrd@z Thu Jan  1 00:00:00 1970
From: Aneesh V <aneesh@ti.com>
Date: Tue, 17 May 2011 15:50:06 +0530
Subject: [U-Boot] [PATCH v3 05/10] armv7: integrate cache maintenance
 support
In-Reply-To: <20110515185534.9B1F01491B06@gemini.denx.de>
References: <1299589658-30896-1-git-send-email-aneesh@ti.com>
	<1305202276-27784-6-git-send-email-aneesh@ti.com>
	<20110515185534.9B1F01491B06@gemini.denx.de>
Message-ID: <4DD24BD6.5060608@ti.com>
List-Id: <u-boot.lists.denx.de>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: u-boot@lists.denx.de

Hi Wolfgang,

On Monday 16 May 2011 12:25 AM, Wolfgang Denk wrote:
> Dear Aneesh V,
>
> In message<1305202276-27784-6-git-send-email-aneesh@ti.com>  you wrote:
>> - Enable I-cache on bootup
>> - Enable MMU and D-cache immediately after relocation
>> 	- Do necessary initialization before enabling d-cache and MMU
>
> Would it be possible to do this even _before_ relocation, so to speed
> up memory accesses during relocation?  Of course, proper invalidates/
> flushes will be needed before jumping to the RAM address, but I guess
> this would save a bit of boot times?

I intentionally kept it after  relocation to avoid un-necessary 
complexities.
Relocation is a case of self-modifying code. In Harvard architectures
like armv7 there will be coherency issues unless we flush the entire
D-cache(range based operation may be equally or more expensive) and
invalidate the entire I-cache.

So, in effect everything has to be flushed to memory before you jump to
the new location. There may be a small advantage because flushing from
cache allows for bursting to the DDR where as bursting is not possible
when d-cache is disabled. But I think this is not worth the trouble.

best regards,
Aneesh