[U-Boot] bootcount: Add dcache flush to bootcount_store()

[Stefan Roese]

Hi!

(added a few more people to the Cc list)

On 17.03.2015 10:00, Holger Brunck wrote:
> Hi Tom,
> 
> On 03/13/2015 03:34 PM, Tom Rini wrote:
>> On Fri, Mar 13, 2015 at 09:48:56AM -0400, Tom Rini wrote:
>>> On Wed, Mar 11, 2015 at 09:51:38AM +0100, Stefan Roese wrote:
>>>
>>>> Without this dcache_flush the updated bootcounter may not be saved to
>>>> its location.
>>>>
>>>> This was detected on an iMX.6 platform using the OCRAM (internal SRAM)
>>>> as bootcounter storage area. And issuing "reset" from within U-Boot
>>>> cause the bootcounter to stay on its initial value.
>>>>
>>>> Signed-off-by: Stefan Roese <sr at denx.de>
>>>> Reviewed-by: Tom Rini <trini at konsulko.com>
>>>
>>> OK, this breaks some platforms:
>>>     powerpc:  +   TQM850L
>>> +(TQM850L) drivers/built-in.o: In function `bootcount_store':
>>> +(TQM850L) build/../drivers/bootcount/bootcount.c:64: undefined reference to `flush_dcache_range'
>>> +(TQM850L) make[1]: *** [u-boot] Error 1
>>> +(TQM850L) make: *** [sub-make] Error 2
>>>
>>> We'll see how many others have the same problem soon and then I'll
>>> decide on nuking the old platforms of holding off on this change.
>>
>> Aside from the TQM 8xx family that Wolfgang owns we have mgcoge and
>> mgcoge3ne also breaking from this
>> (http://patchwork.ozlabs.org/patch/448849/) change.  Wolfgang, Holger,
>> how do you want to proceed?  We either need cache operations or dropping
>> bootcount from the platforms or dropping the platforms.
>>
> 
> we still would like to keep mgcoge and mgcoge3ne support. These boards are still
> in maintenance. Unfortunately this week we are very busy. Next week Valentin or
> myself have planned to find some time to look at this.

I just yesterday noticed this code for mx6:

------------------------- arch/arm/cpu/armv7/mx6/soc.c -------------------------
void enable_caches(void)
{
	...
	/* Enable caching on OCRAM and ROM */
	mmu_set_region_dcache_behaviour(ROMCP_ARB_BASE_ADDR,
					ROMCP_ARB_END_ADDR,
					option);
	mmu_set_region_dcache_behaviour(IRAM_BASE_ADDR,
					IRAM_SIZE,
					option);

So we definitely have the dcache enabled on mx6 in the OCRAM. And this
of course explains, why I need the cache flush operations in the
bootcounter code.

I'm not really sure if we want this area to be cached though. This got
introduced with this patch:

Author: Nitin Garg <nitin.garg at freescale.com>  2014-09-16 20:33:25
Committer: Stefano Babic <sbabic at denx.de>  2014-09-22 16:21:04

    imx: Support i.MX6 High Assurance Boot authentication
    
    When CONFIG_SECURE_BOOT is enabled, the signed images
    like kernel and dtb can be authenticated using iMX6 CAAM.
    The added command hab_auth_img can be used for HAB
    authentication of images. The command takes the image
    DDR location, IVT (Image Vector Table) offset inside
    image as parameters. Detailed info about signing images
    can be found in Freescale AppNote AN4581.
    
    Signed-off-by: Nitin Garg <nitin.garg at freescale.com>

The cache stuff is not mentioned here in this commit log.
Nitin, why did you enable the cache here? Performance reason
only?

If the OCRAM was uncached (again), we could really drop my patch
(this mail thread) with those flush calls. So how should we proceed?
Make this OCRAM area uncached again?

Comments welcome...

Thanks,
Stefan

BTW: I'm on vacation now until 8th April, so please don't expect
any replies in this time.