linux-kernel - [PATCH v4 8/9] i2c: piix4: Add EFCH MMIO support for SMBus port select

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Date:   Sun, 30 Jan 2022 12:41:29 -0600
From:   Terry Bowman <terry.bowman@....com>
To:     <terry.bowman@....com>, <linux@...ck-us.net>,
        <linux-watchdog@...r.kernel.org>, <jdelvare@...e.com>,
        <linux-i2c@...r.kernel.org>, <wsa@...nel.org>,
        <andy.shevchenko@...il.com>, <rafael.j.wysocki@...el.com>
CC:     <linux-kernel@...r.kernel.org>, <wim@...ux-watchdog.org>,
        <rrichter@....com>, <thomas.lendacky@....com>,
        <sudheesh.mavila@....com>, <Nehal-bakulchandra.Shah@....com>,
        <Basavaraj.Natikar@....com>, <Shyam-sundar.S-k@....com>,
        <Mario.Limonciello@....com>
Subject: [PATCH v4 8/9] i2c: piix4: Add EFCH MMIO support for SMBus port select

AMD processors include registers capable of selecting between 2 SMBus
ports. Port selection is made during each user access by writing to
FCH::PM::DECODEEN[smbus0sel]. Change the driver to use MMIO during
SMBus port selection because cd6h/cd7h port I/O is not available on
later AMD processors.

Signed-off-by: Terry Bowman <terry.bowman@....com>
---
 drivers/i2c/busses/i2c-piix4.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index a23c0327e1f6..c5325cadaf55 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -752,10 +752,19 @@ static void piix4_imc_wakeup(void)
 	release_region(KERNCZ_IMC_IDX, 2);
 }
 
-static int piix4_sb800_port_sel(u8 port)
+static int piix4_sb800_port_sel(u8 port, struct sb800_mmio_cfg *mmio_cfg)
 {
 	u8 smba_en_lo, val;
 
+	if (mmio_cfg->use_mmio) {
+		smba_en_lo = ioread8(mmio_cfg->addr + piix4_port_sel_sb800);
+		val = (smba_en_lo & ~piix4_port_mask_sb800) | port;
+		if (smba_en_lo != val)
+			iowrite8(val, mmio_cfg->addr + piix4_port_sel_sb800);
+
+		return (smba_en_lo & piix4_port_mask_sb800);
+	}
+
 	outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
 	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
 
@@ -765,6 +774,7 @@ static int piix4_sb800_port_sel(u8 port)
 
 	return (smba_en_lo & piix4_port_mask_sb800);
 }
+
 /*
  * Handles access to multiple SMBus ports on the SB800.
  * The port is selected by bits 2:1 of the smb_en register (0x2c).
@@ -841,12 +851,12 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 		}
 	}
 
-	prev_port = piix4_sb800_port_sel(adapdata->port);
+	prev_port = piix4_sb800_port_sel(adapdata->port, &adapdata->mmio_cfg);
 
 	retval = piix4_access(adap, addr, flags, read_write,
 			      command, size, data);
 
-	piix4_sb800_port_sel(prev_port);
+	piix4_sb800_port_sel(prev_port, &adapdata->mmio_cfg);
 
 	/* Release the semaphore */
 	outb_p(smbslvcnt | 0x20, SMBSLVCNT);
-- 
2.30.2