linux-kernel - Re: [PATCH] ARM: tegra114: add speedo-based process identification

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Message-ID: <1363588682.4994.223.camel@dahuang-vm>
Date:	Mon, 18 Mar 2013 14:38:02 +0800
From:	Danny Huang <dahuang@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	Joseph Lo <josephl@...dia.com>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: tegra114: add speedo-based process identification

On Sat, 2013-03-16 at 01:36 +0800, Stephen Warren wrote:
> On 03/14/2013 01:40 AM, Danny Huang wrote:
> > Add speedo-based process identifictaion for Tegra114.
> > 
> > Based on the work by:
> > Alex Frid <afrid@...dia.com>
> 
> This code is surprisingly quite a bit simpler than the existing
> tegra30_speedo.c. Are you sure it's complete?

It's complete and working for now. But It may need update if we have
more sku/chip revision in the future.

> > diff --git a/arch/arm/mach-tegra/fuse.c b/arch/arm/mach-tegra/fuse.c
> 
> > @@ -137,6 +138,9 @@ void tegra_init_fuse(void)
> >  		tegra_fuse_spare_bit = TEGRA30_FUSE_SPARE_BIT;
> >  		tegra_init_speedo_data = &tegra30_init_speedo_data;
> >  		break;
> > +	case TEGRA114:
> > +		tegra_init_speedo_data = &tegra114_init_speedo_data;
> > +		break;
> 
> Don't you need to set tegra_fuse_spare_bit there just like all the other
> paths do?
> 

There is no need of spare fuse access for Tegra114 for now.

> > diff --git a/arch/arm/mach-tegra/tegra114_speedo.c b/arch/arm/mach-tegra/tegra114_speedo.c
> 
> > +#define CORE_PROCESS_CORNERS_NUM	2
> > +#define CPU_PROCESS_CORNERS_NUM		2
> > +
> > +enum {
> > +	THRESHOLD_INDEX_0,
> > +	THRESHOLD_INDEX_1,
> > +	THRESHOLD_INDEX_COUNT,
> > +};
> > +
> > +static const u32 core_process_speedos[THRESHOLD_INDEX_COUNT]
> > +	[CORE_PROCESS_CORNERS_NUM] = {
> > +	{1123,     UINT_MAX},
> > +	{0,        UINT_MAX},
> > +};
> > +
> > +static const u32 cpu_process_speedos[THRESHOLD_INDEX_COUNT]
> > +	[CPU_PROCESS_CORNERS_NUM] = {
> > +	{1695,     UINT_MAX},
> > +	{0,        UINT_MAX},
> > +};
> 
> Those enums/tables are a lot smaller than Tegra30. I'm surprised if we
> end up making new chips simpler rather than more complex in this area.
> Are those tables complete?

That's currently all I have. I think we can add some more data in the
future when needed.

> 
> > +static void rev_sku_to_speedo_ids(int rev, int sku, int *threshold)
> > +{
> > +	u32 tmp;
> > +
> > +	switch (sku) {
> > +	case 0x00:
> > +	case 0x10:
> > +	case 0x05:
> > +	case 0x06:
> > +		tegra_cpu_speedo_id = 1;
> > +		tegra_soc_speedo_id = 0;
> > +		*threshold = THRESHOLD_INDEX_0;
> > +		break;
> > +
> > +	case 0x03:
> > +	case 0x04:
> > +		tegra_cpu_speedo_id = 2;
> > +		tegra_soc_speedo_id = 1;
> > +		*threshold = THRESHOLD_INDEX_1;
> > +		break;
> > +
> > +	default:
> > +		pr_err("Tegra114 Unknown SKU %d\n", sku);
> > +		tegra_cpu_speedo_id = 0;
> > +		tegra_soc_speedo_id = 0;
> > +		*threshold = THRESHOLD_INDEX_0;
> > +		break;
> > +	}
> > +
> > +	if (rev == TEGRA_REVISION_A01) {
> > +		tmp = tegra_fuse_readl(0x270) << 1;
> > +		tmp |= tegra_fuse_readl(0x26c);
> > +		if (!tmp)
> > +			tegra_cpu_speedo_id = 0;
> > +	}
> > +}
> 
> That's also a lot simpler than Tegra30. Are all those SKUs really valid
> for all chip revisions including A01 where the 0x270/0x26c fuses are clear?

Yes, currently the 0x26c/0x270 value affects all sku of A01 chips.

> If life really is this simple, then I should be happy:-) But I just want
> to check that this code really is accurate.
> 
> > +void tegra114_init_speedo_data(void)
> 
> The Tegra30 code has a couple BUILD_BUG_ON() here to ensure that the
> size of the {cpu,core}_process_speedos arrays match
> THRESHOLD_INDEX_COUNT. It'd be good to be consistent here.

I'll put the BUILD_BUG_ON back and make them consistent with Tegra30 in
next version. Thanks.

> 
> In general, the implementation of tegra114_init_speedo_data() is quite
> different from that of the existing tegra30_init_speedo_data(). It'd be
> nice if they were as similar as possible in structure so they could be
> easily compared. Can you take a look at the two and see if any changes
> are warranted in this patch?
> --
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