From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Date: Tue, 19 May 2015 22:01:18 +0000 Subject: Re: [PATCH] ARM: v7 setup function should invalidate L1 cache Message-Id: <555BB2AE.50302@gmail.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On 19/05/15 09:12, Russell King wrote: > All ARMv5 and older CPUs invalidate their caches in the early assembly > setup function, prior to enabling the MMU. This is because the L1 > cache should not contain any data relevant to the execution of the > kernel at this point; all data should have been flushed out to memory. > > This requirement should also be true for ARMv6 and ARMv7 CPUs - indeed, > these typically do not search their caches when caching is disabled (as > it needs to be when the MMU is disabled) so this change should be safe. > > ARMv7 allows there to be CPUs which search their caches while caching is > disabled, and it's permitted that the cache is uninitialised at boot; > for these, the architecture reference manual requires that an > implementation specific code sequence is used immediately after reset > to ensure that the cache is placed into a sane state. Such > functionality is definitely outside the remit of the Linux kernel, and > must be done by the SoC's firmware before _any_ CPU gets to the Linux > kernel. > > Changing the data cache clean+invalidate to a mere invalidate allows us > to get rid of a lot of platform specific hacks around this issue for > their secondary CPU bringup paths - some of which were buggy. For brcmstb: Reviewed-by: Florian Fainelli Tested-by: Florian Fainelli -- Florian