linux-kernel - Re: [PATCH v2 2/8] arm/tegra: prepare early init for multiple tegra variants

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Message-ID: <20111107123630.GO29978@tbergstrom-lnx.Nvidia.com>
Date:	Mon, 7 Nov 2011 14:36:30 +0200
From:	Peter De Schrijver <pdeschrijver@...dia.com>
To:	Colin Cross <ccross@...roid.com>
CC:	Russell King <linux@....linux.org.uk>,
	Olof Johansson <olof@...om.net>,
	Stephen Warren <swarren@...dia.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v2 2/8] arm/tegra: prepare early init for multiple
 tegra variants

On Thu, Nov 03, 2011 at 10:21:16AM +0100, Peter De Schrijver wrote:
> On Wed, Nov 02, 2011 at 07:30:43PM +0100, Colin Cross wrote:
> > On Wed, Nov 2, 2011 at 7:09 AM, Peter De Schrijver
> > <pdeschrijver@...dia.com> wrote:
> > > This patch splits the early init code in a common and a tegra20 specific part.
> > > L2 cache initialization is generalized and discovers the cache associativity
> > > at runtime.
> > >
> > > Signed-off-by: Peter De Schrijver <pdeschrijver@...dia.com>
> > > ---
> > <snip>
> > 
> > > -static __initdata struct tegra_clk_init_table common_clk_init_table[] = {
> > > +void (*arch_reset)(char mode, const char *cmd) = tegra_assert_system_reset;
> > > +
> > This is unrelated to the patch description?
> > 
> 
> This is a left over from the past. Will be removed from the next version.
> 
> > > +static __initdata struct tegra_clk_init_table tegra20_clk_init_table[] = {
> > >        /* name         parent          rate            enabled */
> > >        { "clk_m",      NULL,           0,              true },
> > >        { "pll_p",      "clk_m",        216000000,      true },
> > > @@ -59,25 +61,34 @@ static __initdata struct tegra_clk_init_table common_clk_init_table[] = {
> > >        { NULL,         NULL,           0,              0},
> > >  };
> > >
> > > -static void __init tegra_init_cache(void)
> > > +static void __init tegra_init_cache(u32 tag_latency, u32 data_latency)
> > >  {
> > >  #ifdef CONFIG_CACHE_L2X0
> > >        void __iomem *p = IO_ADDRESS(TEGRA_ARM_PERIF_BASE) + 0x3000;
> > > +       u32 aux_ctrl;
> > > +
> > > +       writel_relaxed(tag_latency, p + L2X0_TAG_LATENCY_CTRL);
> > > +       writel_relaxed(data_latency, p + L2X0_DATA_LATENCY_CTRL);
> > >
> > > -       writel_relaxed(0x331, p + L2X0_TAG_LATENCY_CTRL);
> > > -       writel_relaxed(0x441, p + L2X0_DATA_LATENCY_CTRL);
> > > +       aux_ctrl = readl(p + L2X0_CACHE_TYPE);
> > > +       aux_ctrl = (aux_ctrl & 0x700) << (17-8);
> > 
> > If I'm interpreting the PL310 TRM correctly, the cache associativity
> > value in the L2X0_CACHE_TYPE register is read from the aux control
> > register, so this is just leaving the existing value in place.  If the
> > value is not being modified, just take it out of the aux_ctrl mask
> > passed to l2x0_init.
> > 
> 
> This seems to work fine on our android kernels though. Need to dig deeper
> what's going on here.

Doesn't seem to be that simple on tegra. The L2X0_CACHE_TYPE can indicate a
different waysize depending on fuses.

Cheers,

Peter.

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