Re: [PATCH 1/3] ARM: shmobile: armadillo800eva: enable all errata for cache on defconfig

From: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
To: linux-sh@vger.kernel.org
Subject: Re: [PATCH 1/3] ARM: shmobile: armadillo800eva: enable all errata for cache on defconfig
Date: Mon, 04 Mar 2013 00:42:08 +0000	[thread overview]
Message-ID: <87d2vgq9lx.wl%kuninori.morimoto.gx@renesas.com> (raw)
In-Reply-To: <1346808893-14124-2-git-send-email-horms@verge.net.au>

Hi Simon

> > > > > Some errata for cache had not enabled on current
> > > > > Armadillo800eva defconfig.
> > > > > This patch enables these.
> > > > > Special thanks to Ishiyama-san
> > > > 
> > > > It seems to me that it would be better to handle these in Kconfig
> > > > to enable them on an SoC or board basis.
> > > > 
> > > > The reason is that I would like to move away from per-board defconfigs
> > > > and towards a more consolidated defconfig. And in that case it will
> > > > be more difficult to know which ERRATA are needed for each board and SoC.
> > > > 
> > > > Obviously this thinking is open to review and it implies that
> > > > several board defconfigs should be updated.
> > 
> > We used defconfig selection for CPU/board settings before.
> > But Kconfig selection for ERRATA make sense.
> > 
> > Do you want to me to send v2 patch which use Kconfig ?
> > Or do you do that ?
> 
> I'd like you to send v2 if possible.

OK, but I noticed that it will be complex if we select these ERRATA on Kconfig,
Because, these ERRATAs dependency.

Ex)
config PL310_ERRATA_588369
	bool "PL310 errata: Clean & Invalidate maintenance operations do not invalidate clean lines"
	depends on CACHE_L2X0

It depends on CACHE_L2X0, but this CACHE_L2X0 selection is depend on user,
this means that there is no guarantee that CACHE_L2X0 is selected.
Then, the Kconfig will be...

        select PL310_ERRATA_588369 if CACHE_L2X0

And more complex ERRARA dependency is...

config ARM_ERRATA_742230
	bool "ARM errata: DMB operation may be faulty"
	depends on CPU_V7 && SMP
	depends on !ARCH_MULTIPLATFORM

Of course I can use above style on Kconfig,
but my worry is we will have unknown trouble
if someone updated these ERRATA implementation and dependency
in the future...

This is example, but I tested below.
This means we can select unnecessary settings on Kconfig ...

----------------
config ARM_ERRATA_326103
	bool "ARM errata: FSR write bit incorrect on a SWP to read-only memory"
=>	depends on CPU_V6
        ...

config ARCH_R8A7740
	bool "R-Mobile A1 (R8A77400)"
	select ARCH_WANT_OPTIONAL_GPIOLIB
=>	select CPU_V7
=>	select ARM_ERRATA_326103
        ...

> grep ERRATA .config
CONFIG_ARM_ERRATA_326103=y
----------------------

Best regards
---
Kuninori Morimoto