From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: OMAP3 L2/outer cache enabled in kernel (after being disabled by uBoot)?
Date: Tue, 17 Jan 2012 13:39:18 +0000 [thread overview]
Message-ID: <20120117133918.GE11475@arm.com> (raw)
In-Reply-To: <CAMQu2gyft96O61Toja-h-MPpzFTQ8dpJWauw3o6qcPQBXEC_6A@mail.gmail.com>
On Tue, Jan 17, 2012 at 12:40:54PM +0000, Shilimkar, Santosh wrote:
> On Tue, Jan 17, 2012 at 1:27 PM, Aneesh V <aneesh@ti•com> wrote:
> > Hi Catalin,
> >
> >
> > On Tuesday 17 January 2012 05:41 PM, Catalin Marinas wrote:
> >>
> >> On Tue, Jan 17, 2012 at 08:54:44AM +0000, Joe Woodward wrote:
> >>>
> >>> So, is the upshot of this that the kernel isn't going to be in a
> >>> position to enable the L2/outer cache on OMAP3 (due to the need for
> >>> hacky/unmaintainable code)?
> >>>
> >>> Hence the bootloader/uBoot had better leave it enabled...
> >>
> >> It could but the Linux decompressor needs to be aware and either flush
> >> the L2 (more difficult as it doesn't have all the device information) or
> >
> > Cortex-A8 is aware of L2$ and can flush it, isn't it?
> >
> >> set the page table attributes to outer non-cacheable (TEX[2:0] = 0b100).
> >
> > If the above is right, this is not needed right?
>
> Well the L2 can be configured as inner or outer, so above
> alone won't work.
>
> Boot-loader disabling L2 cache ( all caches) is still right thing
> and that's what kernel expect.
>
> Since the early kernel code can't be patches for A8, may be
> delaying L2 enabled would work.
Ah, I missed the fact that the L2 is an inner cache on OMAP3+A8. In this
case, I would argue to just leave it enabled since as long as the MMU is
off it won't be accessed. Why does U-Boot need to disable the L2 (I
suspect via some auxiliary control register)?
> But then on A15, we are back to square one since there is no
> control to turn ON/OFF l2 cache.
Well, it's an inner cache, it gets disabled/enabled via the SCTLR.M bit
as is the L1 cache. It does not need to be disabled independently.
> On A15 infact there are other CP15 registers which needs to be set
> before MMU is enabled to have best configuration.
Yes, there are, and my view is that it is up to the platform firmware to
set things right.
--
Catalin
next prev parent reply other threads:[~2012-01-17 13:39 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <WC20120116100344.4204CC@terrafix.co.uk>
2012-01-16 10:18 ` OMAP3 L2/outer cache enabled in kernel (after being disabled by uBoot)? Shilimkar, Santosh
2012-01-16 10:59 ` Russell King - ARM Linux
2012-01-16 12:43 ` Shilimkar, Santosh
2012-01-16 13:13 ` Russell King - ARM Linux
2012-01-16 13:22 ` Shilimkar, Santosh
2012-01-17 12:01 ` Aneesh V
[not found] ` <WC20120117085444.17057E@terrafix.co.uk>
2012-01-17 12:11 ` Catalin Marinas
2012-01-17 12:27 ` Aneesh V
2012-01-17 12:40 ` Shilimkar, Santosh
2012-01-17 13:39 ` Catalin Marinas [this message]
2012-01-17 13:58 ` Shilimkar, Santosh
2012-01-17 16:27 ` Catalin Marinas
2012-01-17 17:27 ` Shilimkar, Santosh
2012-01-17 19:39 ` Nicolas Pitre
2012-01-17 20:27 ` Shilimkar, Santosh
2012-01-17 20:45 ` Nicolas Pitre
2012-01-17 20:57 ` Nicolas Pitre
2012-01-17 20:58 ` Shilimkar, Santosh
2012-01-17 21:02 ` Nicolas Pitre
2012-01-18 8:43 ` Shilimkar, Santosh
2012-01-17 21:15 ` Russell King - ARM Linux
2012-01-17 19:47 ` Russell King - ARM Linux
2012-01-17 20:11 ` Shilimkar, Santosh
2012-01-17 20:48 ` Russell King - ARM Linux
2012-01-17 19:43 ` Russell King - ARM Linux
[not found] ` <WC20120120085711.330803@terrafix.co.uk>
2012-01-27 17:30 ` Catalin Marinas
2012-01-31 5:21 ` Aneesh V
2012-01-31 7:31 ` Catalin Marinas
2012-01-31 7:38 ` Shilimkar, Santosh
2012-01-31 8:54 ` Catalin Marinas
2012-01-31 9:05 ` Shilimkar, Santosh
2012-01-31 9:53 ` Catalin Marinas
2012-01-31 10:10 ` Russell King - ARM Linux
2012-01-31 12:10 ` Catalin Marinas
2012-01-31 18:09 ` Nicolas Pitre
2012-02-02 14:32 ` Catalin Marinas
2012-02-02 14:49 ` Russell King - ARM Linux
2012-02-02 15:10 ` Catalin Marinas
2012-01-31 9:56 ` Russell King - ARM Linux
2012-01-31 10:51 ` Shilimkar, Santosh
2012-01-31 18:27 ` Nicolas Pitre
2012-02-01 7:12 ` Shilimkar, Santosh
2012-01-17 14:18 ` Grazvydas Ignotas
2012-01-17 13:41 ` Catalin Marinas
2012-01-17 13:54 ` Aneesh V
2012-01-17 14:23 ` Måns Rullgård
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