linux-kernel - Re: [PATCH] x86: CPU detection for RDC System-on-Chip

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Date:	Mon, 17 May 2010 13:40:42 +0200
From:	Florian Fainelli <florian@...nwrt.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, mingo@...e.hu,
	"linux-kernel" <linux-kernel@...r.kernel.org>, andi@...stfloor.org
Subject: Re: [PATCH] x86: CPU detection for RDC System-on-Chip

On Monday 17 May 2010 00:07:48 H. Peter Anvin wrote:
> On 05/16/2010 06:21 AM, Florian Fainelli wrote:
> > diff --git a/arch/x86/kernel/cpu/rdc.c b/arch/x86/kernel/cpu/rdc.c
> > new file mode 100644
> > index 0000000..909c2b5
> > --- /dev/null
> > +++ b/arch/x86/kernel/cpu/rdc.c
> > @@ -0,0 +1,71 @@
> > +/*
> > + * See Documentation/x86/rdc.txt
> > + *
> > + * mark@...feros.com
> > + */
> > +
> > +#include <linux/pci.h>
> > +#include <asm/pci-direct.h>
> > +#include "cpu.h"
> > +
> > +
> > +static void __cpuinit rdc_identify(struct cpuinfo_x86 *c)
> > +{
> > +	u16 vendor, device;
> > +	u32 customer_id;
> > +
> > +	if (!early_pci_allowed())
> > +		return;
> > +
> > +	/* RDC CPU is SoC (system-on-chip), Northbridge is always present */
> > +	vendor = read_pci_config_16(0, 0, 0, PCI_VENDOR_ID);
> > +	device = read_pci_config_16(0, 0, 0, PCI_DEVICE_ID);
> > +
> > +	if (vendor != PCI_VENDOR_ID_RDC || device != 
PCI_DEVICE_ID_RDC_R6020)
> > +		return;  /* not RDC */
> > +	/*
> > +	 * NB: We could go on and check other devices, e.g. r6040 NIC, but
> > +	 * that's probably overkill
> > +	 */
> > +
> > +	customer_id = read_pci_config(0, 0, 0, 0x90);
> > +
> > +	switch (customer_id) {
> > +		/* id names are from RDC */
> > +	case 0x00321000:
> > +		strcpy(c->x86_model_id, "R3210/R3211");
> > +		break;
> > +	case 0x00321001:
> > +		strcpy(c->x86_model_id, "AMITRISC20000/20010");
> > +		break;
> > +	case 0x00321002:
> > +		strcpy(c->x86_model_id, "R3210X/Edimax");
> > +		break;
> > +	case 0x00321003:
> > +		strcpy(c->x86_model_id, "R3210/Kcodes");
> > +		break;
> > +	case 0x00321004:  /* tested */
> > +		strcpy(c->x86_model_id, "S3282/CodeTek");
> > +		break;
> > +	case 0x00321007:
> > +		strcpy(c->x86_model_id, "R8610");
> > +		break;
> > +	default:
> > +		pr_info("RDC CPU: Unrecognised Customer ID (0x%x) please "
> > +			"report to: linux-kernel@...r.kernel.org\n",
> > +			customer_id);
> > +		break;
> 
> This pr_info() is completely useless... reporting things to LKML is very
> likely to get lost in the din.  If someone (like yourself) wants to be
> the maintainer for it that's one thing, otherwise it's probably better
> to tell them to file a bugzilla... or just report it as "unknown" like
> we do for all other CPU vendors.
> 
> > +	}
> > +
> > +	strcpy(c->x86_vendor_id, "RDC");
> > +	c->x86_vendor = X86_VENDOR_RDC;
> > +}
> > +
> > +static const struct cpu_dev __cpuinitconst rdc_cpu_dev = {
> > +	.c_vendor	= "RDC",
> > +	.c_ident	= { "RDC" },
> > +	.c_identify	= rdc_identify,
> > +	.c_x86_vendor	= X86_VENDOR_RDC,
> > +};
> > +
> > +cpu_dev_register(rdc_cpu_dev);
> 
> .c_ident here is bogus: c_ident is supposed to represent the CPUID
> string, but this device apparently doesn't have CPUID.

What do you suggest to use instead? Shall I put the x86_model_id there?

> 
> This adds at least one PCI reference to every boot on every device.  As
> such, at least please read vendor and device as a single 32-bit
> reference.  Since this identification isn't actually used for any real
> purpose (like workarounds) we could also set it up as a PCI quirk... but
> it's probably better to just keep the same code flow.
> 
> 	-hpa
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