Re: [PATCH v3 7/9] i2c: piix4: Add EFCH MMIO support to SMBus base address detect

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Terry Bowman <terry.bowman@amd.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	linux-watchdog@vger.kernel.org, Jean Delvare <jdelvare@suse.com>,
	linux-i2c <linux-i2c@vger.kernel.org>,
	Wolfram Sang <wsa@kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Robert Richter <rrichter@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	sudheesh.mavila@amd.com, "Shah,
	Nehal-bakulchandra" <Nehal-bakulchandra.Shah@amd.com>,
	Basavaraj Natikar <Basavaraj.Natikar@amd.com>,
	Shyam Sundar S K <Shyam-sundar.S-k@amd.com>,
	Mario Limonciello <Mario.Limonciello@amd.com>
Subject: Re: [PATCH v3 7/9] i2c: piix4: Add EFCH MMIO support to SMBus base address detect
Date: Thu, 20 Jan 2022 13:27:12 +0200	[thread overview]
Message-ID: <CAHp75VdtnOuBK1ctkjO59vujopCrQ+MQ_LyBB+Mi2HJk4HaJuQ@mail.gmail.com> (raw)
In-Reply-To: <20220119230626.31560-8-terry.bowman@amd.com>

On Thu, Jan 20, 2022 at 1:07 AM Terry Bowman <terry.bowman@amd.com> wrote:
>
> The EFCH SMBus controller's base address is determined using details in
> FCH::PM::DECODEEN[smbusasfiobase] and FCH::PM::DECODEEN[smbusasfioen].
> This code also writes to FCH::PM::ISACONTROL[mmioen] to enable MMIO
> decoding. These register fields were accessed using cd6h/cd7h port I/O.
> cd6h/cd7h port I/O is no longer available in later AMD processors.
> Change base address detection to use MMIO instead of port I/O cd6h/cd7h.

...

> +       if (mmio_cfg.use_mmio) {

> +               iowrite32(ioread32(mmio_cfg.addr + 4) | SB800_PIIX4_FCH_PM_DECODEEN_MMIO,
> +                         mmio_cfg.addr + 4);

Can you split this to three lines (with the help of a temporary variable)?

> +               smba_en_lo = ioread8(mmio_cfg.addr);
> +               smba_en_hi = ioread8(mmio_cfg.addr + 1);

This makes me wonder if we can replace these two by defining

  u16 smba_en;

(below also may be easily adjusted for it).

> +       } else {
> +               outb_p(smb_en, SB800_PIIX4_SMB_IDX);
> +               smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
> +               outb_p(smb_en + 1, SB800_PIIX4_SMB_IDX);
> +               smba_en_hi = inb_p(SB800_PIIX4_SMB_IDX + 1);
> +       }
>
>         piix4_sb800_region_release(&PIIX4_dev->dev, &mmio_cfg);

-- 
With Best Regards,
Andy Shevchenko