From: Marco Stornelli <marco.stornelli@coritel.it>
To: Robert Woodworth <rwoodworth@securics.com>
Cc: linuxppc-embedded <linuxppc-embedded@ozlabs.org>
Subject: Re: Cache control
Date: Fri, 17 Oct 2008 09:18:42 +0200 [thread overview]
Message-ID: <48F83C52.3010308@coritel.it> (raw)
In-Reply-To: <1BA180A8-1655-4F10-ADDD-E5667DE182BE@securics.com>
Hi Robert,
Robert Woodworth ha scritto:
> I have a Virtex4 VF60 device with 256MB DDR2.
>
> I have told the Linux kernel that the device has only 128MB and its
> working fine.
How? Have you used the mem kernel option?
There is an HDL module that is populating the next 16MB
> with sensor data (0x08000000 - 0x09000000) I mapped the area into my
> driver via `ioremap()` and also via `mmap / remap_pfn_range()` It works
> fine.
>
> I know that PPC cache regions work in 128MB blocks. I assume that the
> kernel bootup is turning on cache in the first 128, because it thinks
> that its the full RAM range, and not cached in the next 128MB.
>
> I know that if I declare the area cached, and invalidate the region
> before I read it, the reads should be much faster than if it's not cached.
>
>
> How can I control if the area is cached? and then invalidate it when new
> data arrives?
If you use the ioremap, it provides non-cacheable guarded mappings,
indeed it calls __ioremap with _PAGE_NO_CACHE and _PAGE_GUARDED flags.
You can try to call directly __ioremap with the proper flags.
>
> Is there a PPC/Linux API call to declare the region cached and
> invalidate regions before read?
>
Yes, of course. You can see the arch/powerpc/include/asm/cacheflush.h
file to view the API to manage the cache.
>
>
>
>
> Rob.
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>
Regards,
--
Marco Stornelli
Embedded Software Engineer
CoRiTeL - Consorzio di Ricerca sulle Telecomunicazioni
http://www.coritel.it
marco.stornelli@coritel.it
+39 06 72582838
next prev parent reply other threads:[~2008-10-17 7:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-16 15:57 Cache control Robert Woodworth
2008-10-17 7:18 ` Marco Stornelli [this message]
2008-10-18 6:32 ` Grant Likely
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