linux-kernel - Re: [PATCH v3 2/4] i2c: piix4: Move SB800_PIIX4_FCH_PM_ADDR definition to amd

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Message-ID: <Z_wRPb5H5hi6jmxN@gmail.com>
Date: Sun, 13 Apr 2025 21:32:13 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Mario Limonciello <superm1@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>, Jean Delvare <jdelvare@...e.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Jonathan Corbet <corbet@....net>,
	Mario Limonciello <mario.limonciello@....com>,
	Yazen Ghannam <yazen.ghannam@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Shyam Sundar S K <Shyam-sundar.S-k@....com>,
	Hans de Goede <hdegoede@...hat.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" <linux-i2c@...r.kernel.org>,
	"open list:AMD PMC DRIVER" <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] i2c: piix4: Move SB800_PIIX4_FCH_PM_ADDR
 definition to amd_node.h


* Mario Limonciello <superm1@...nel.org> wrote:

> 
> 
> On 4/13/25 03:44, Ingo Molnar wrote:
> > 
> > * Ingo Molnar <mingo@...nel.org> wrote:
> > 
> > > 
> > > * Borislav Petkov <bp@...en8.de> wrote:
> > > 
> > > > I was aiming more for a header which contains non-CPU defines -
> > > > i.e., platform. But the FCH is only one part of that platform. But
> > > > let's start with amd/fch.h - "amd/" subpath element would allow us
> > > > to trivially put other headers there too - and see where it gets
> > > > us. We can (and will) always refactor later if needed...
> > > 
> > > Yeah, agreed on opening the <asm/amd/> namespace for this.
> > 
> > Here's a tree that establishes <asm/amd/> and moves existing headers
> > there:
> > 
> >    git://git.kernel.org/pub/scm/linux/kernel/git/mingo/tip.git WIP.x86/platform
> > 
> > Mario, could you base your series on top of this tree?
> > 
> 
> Sure.
> 
> One problem that I notice though is that by using <asm/amd/fch.h> that
> drivers/i2c/busses/i2c-piix4.c has some compile failures on non-x86.

Hm, should these I2C drivers even be built on non-x86 systems?

> 1) Add '#if CONFIG_X86' around all related code.
> 
> 2) Move applicable code to drivers/i2c/busses/i2c-amd-fch.c (similar to how
> we have i2c-amd-asf-plat.c) but modify drivers/i2c/busses/Makefile to only
> compile it for x86.
> 
> 3) Idea two but also add a new Kconfig for CONFIG_I2C_AMD_FCH that depends
> on CONFIG_X86.
> 
> I am /leaning/ on the refactor with idea 3.

I'd go for something like the patch below. There's X86 dependencies for 
other I2C drivers as well, so it's not unprecedented.

Thanks,

	Ingo

==============>
 drivers/i2c/busses/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 83c88c79afe2..bbbd6240fa6e 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -200,7 +200,7 @@ config I2C_ISMT
 
 config I2C_PIIX4
 	tristate "Intel PIIX4 and compatible (ATI/AMD/Serverworks/Broadcom/SMSC)"
-	depends on PCI && HAS_IOPORT
+	depends on PCI && HAS_IOPORT && X86
 	select I2C_SMBUS
 	help
 	  If you say yes to this option, support will be included for the Intel