[PATCH] i2c: piix4: Replace piix4_smbus driver's cd6h/cd7h port io accesses with mmio accesses

[Terry Bowman]

cd6h/cd7h port io can be disabled on recent AMD hardware. Read accesses to
disabled cd6h/cd7h will return F's and written data is dropped. The
recommended workaround to handle disabled cd6h/cd7h port io is replacing
with MMIO accesses. Support for MMIO has been available as an alternative
cd6h/cd7h access method since at least smbus controller with PCI revision
0x59. The piix4_smbus driver uses cd6h/cd7h port io in the following 2
cases and requires updating to use MMIO:

1. The FCH::PM::DECODEEN[smbusasfiobase] and FCH::PM::DECODEEN[0..7]
   register fields are used to discover the smbus port io address.
2. During access requests the piix4_smbus driver enables the requested port
   if it is not already enabled. The downstream port is enabled through the
   FCH::PM::DECODEEN[smbus0sel] register.

Signed-off-by: Terry Bowman <Terry.Bowman@xxxxxxx>
Cc: Jean Delvare <jdelvare@xxxxxxxx>
Cc: Thomas Lendacky <Thomas.Lendacky@xxxxxxx>
Cc: linux-i2c@xxxxxxxxxxxxxxx
---
diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index 8c1b31ed0c42..2d2105793944 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -77,6 +77,7 @@
 
 /* SB800 constants */
 #define SB800_PIIX4_SMB_IDX		0xcd6
+#define SB800_PIIX4_SMB_MAP_SIZE	2
 
 #define KERNCZ_IMC_IDX			0x3e
 #define KERNCZ_IMC_DATA			0x3f
@@ -97,6 +98,12 @@
 #define SB800_PIIX4_PORT_IDX_MASK_KERNCZ	0x18
 #define SB800_PIIX4_PORT_IDX_SHIFT_KERNCZ	3
 
+#define SB800_PIIX4_FCH_PM_DECODEEN_MMIO_EN     BIT(1)
+#define SB800_PIIX4_FCH_PM_ADDR                 0xFED80300
+#define SB800_PIIX4_FCH_PM_SIZE                 8
+
+#define AMD_PCI_SMBUS_REVISION_MMIO             0x59
+
 /* insmod parameters */
 
 /* If force is set to anything different from 0, we forcibly enable the
@@ -155,6 +162,12 @@ static const char *piix4_main_port_names_sb800[PIIX4_MAX_ADAPTERS] = {
 };
 static const char *piix4_aux_port_name_sb800 = " port 1";
 
+struct sb800_mmio_cfg {
+	void __iomem *addr;
+	struct resource *res;
+	bool use_mmio;
+};
+
 struct i2c_piix4_adapdata {
 	unsigned short smba;
 
@@ -162,8 +175,72 @@ struct i2c_piix4_adapdata {
 	bool sb800_main;
 	bool notify_imc;
 	u8 port;		/* Port number, shifted */
+	struct sb800_mmio_cfg mmio_cfg;
 };
 
+static int piix4_sb800_region_setup(struct device *dev,
+				    struct sb800_mmio_cfg *mmio_cfg)
+{
+	if (mmio_cfg->use_mmio) {
+		struct resource *res;
+		void __iomem *addr;
+
+		res = request_mem_region(SB800_PIIX4_FCH_PM_ADDR,
+					 SB800_PIIX4_FCH_PM_SIZE,
+					 "sb800_piix4_smb");
+		if (!res) {
+			dev_err(dev,
+				"SMB base address memory region 0x%x already in use.\n",
+				SB800_PIIX4_FCH_PM_ADDR);
+			return -EBUSY;
+		}
+
+		addr = ioremap(SB800_PIIX4_FCH_PM_ADDR,
+			       SB800_PIIX4_FCH_PM_SIZE);
+		if (!addr) {
+			release_resource(res);
+			dev_err(dev, "SMB base address mapping failed.\n");
+			return -ENOMEM;
+		}
+
+		mmio_cfg->res = res;
+		mmio_cfg->addr = addr;
+	} else {
+		if (!request_muxed_region(SB800_PIIX4_SMB_IDX,
+					  SB800_PIIX4_SMB_MAP_SIZE,
+					  "sb800_piix4_smb")) {
+			dev_err(dev,
+				"SMB base address index region 0x%x already in use.\n",
+				SB800_PIIX4_SMB_IDX);
+			return -EBUSY;
+		}
+	}
+
+	return 0;
+}
+
+static void piix4_sb800_region_release(struct device *dev,
+				       struct sb800_mmio_cfg *mmio_cfg)
+{
+	if (mmio_cfg->use_mmio) {
+		iounmap(mmio_cfg->addr);
+		mmio_cfg->addr = NULL;
+
+		release_resource(mmio_cfg->res);
+		mmio_cfg->res = NULL;
+	} else {
+		release_region(SB800_PIIX4_SMB_IDX,
+			       SB800_PIIX4_SMB_MAP_SIZE);
+	}
+}
+
+static bool piix4_sb800_use_mmio(struct pci_dev *PIIX4_dev)
+{
+	return (PIIX4_dev->vendor == PCI_VENDOR_ID_AMD &&
+		PIIX4_dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS &&
+		PIIX4_dev->revision >= AMD_PCI_SMBUS_REVISION_MMIO);
+}
+
 static int piix4_setup(struct pci_dev *PIIX4_dev,
 		       const struct pci_device_id *id)
 {
@@ -263,12 +340,58 @@ static int piix4_setup(struct pci_dev *PIIX4_dev,
 	return piix4_smba;
 }
 
+static int piix4_setup_sb800_smba(struct pci_dev *PIIX4_dev,
+				  u8 smb_en,
+				  u8 aux,
+				  u8 *smb_en_status,
+				  unsigned short *piix4_smba)
+{
+	struct sb800_mmio_cfg mmio_cfg;
+	u8 smba_en_lo;
+	u8 smba_en_hi;
+	int retval;
+
+	mmio_cfg.use_mmio = piix4_sb800_use_mmio(PIIX4_dev);
+
+	retval = piix4_sb800_region_setup(&PIIX4_dev->dev, &mmio_cfg);
+	if (retval)
+		return retval;
+
+	if (mmio_cfg.use_mmio) {
+		iowrite32(ioread32(mmio_cfg.addr + 4) | SB800_PIIX4_FCH_PM_DECODEEN_MMIO_EN,
+			  mmio_cfg.addr + 4);
+
+		smba_en_lo = ioread8(mmio_cfg.addr);
+		smba_en_hi = ioread8(mmio_cfg.addr + 1);
+	} 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);
+
+	if (!smb_en) {
+		*smb_en_status = smba_en_lo & 0x10;
+		*piix4_smba = smba_en_hi << 8;
+		if (aux)
+			*piix4_smba |= 0x20;
+	} else {
+		*smb_en_status = smba_en_lo & 0x01;
+		*piix4_smba = ((smba_en_hi << 8) | smba_en_lo) & 0xffe0;
+	}
+
+	return retval;
+}
+
 static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
 			     const struct pci_device_id *id, u8 aux)
 {
 	unsigned short piix4_smba;
-	u8 smba_en_lo, smba_en_hi, smb_en, smb_en_status, port_sel;
+	u8 smb_en, smb_en_status, port_sel;
 	u8 i2ccfg, i2ccfg_offset = 0x10;
+	int retval;
 
 	/* SB800 and later SMBus does not support forcing address */
 	if (force || force_addr) {
@@ -290,29 +413,10 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
 	else
 		smb_en = (aux) ? 0x28 : 0x2c;
 
-	if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb")) {
-		dev_err(&PIIX4_dev->dev,
-			"SMB base address index region 0x%x already in use.\n",
-			SB800_PIIX4_SMB_IDX);
-		return -EBUSY;
-	}
-
-	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);
-
-	release_region(SB800_PIIX4_SMB_IDX, 2);
-
-	if (!smb_en) {
-		smb_en_status = smba_en_lo & 0x10;
-		piix4_smba = smba_en_hi << 8;
-		if (aux)
-			piix4_smba |= 0x20;
-	} else {
-		smb_en_status = smba_en_lo & 0x01;
-		piix4_smba = ((smba_en_hi << 8) | smba_en_lo) & 0xffe0;
-	}
+	retval = piix4_setup_sb800_smba(PIIX4_dev, smb_en,
+					aux, &smb_en_status, &piix4_smba);
+	if (retval)
+		return retval;
 
 	if (!smb_en_status) {
 		dev_err(&PIIX4_dev->dev,
@@ -662,6 +766,28 @@ static void piix4_imc_wakeup(void)
 	release_region(KERNCZ_IMC_IDX, 2);
 }
 
+static int piix4_sb800_port_sel(u8 port, struct sb800_mmio_cfg *mmio_cfg)
+{
+	u8 smba_en_lo;
+
+	if (mmio_cfg->use_mmio) {
+		smba_en_lo = ioread8(mmio_cfg->addr + piix4_port_sel_sb800);
+
+		if ((smba_en_lo & piix4_port_mask_sb800) != port)
+			iowrite8((smba_en_lo & ~piix4_port_mask_sb800) | port,
+				 mmio_cfg->addr + piix4_port_sel_sb800);
+	} else {
+		outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
+		smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
+
+		if ((smba_en_lo & piix4_port_mask_sb800) != port)
+			outb_p((smba_en_lo & ~piix4_port_mask_sb800) | port,
+			       SB800_PIIX4_SMB_IDX + 1);
+	}
+
+	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).
@@ -678,12 +804,12 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 	unsigned short piix4_smba = adapdata->smba;
 	int retries = MAX_TIMEOUT;
 	int smbslvcnt;
-	u8 smba_en_lo;
-	u8 port;
+	u8 prev_port;
 	int retval;
 
-	if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb"))
-		return -EBUSY;
+	retval = piix4_sb800_region_setup(&adap->dev, &adapdata->mmio_cfg);
+	if (retval)
+		return retval;
 
 	/* Request the SMBUS semaphore, avoid conflicts with the IMC */
 	smbslvcnt  = inb_p(SMBSLVCNT);
@@ -738,18 +864,12 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 		}
 	}
 
-	outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
-	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
-
-	port = adapdata->port;
-	if ((smba_en_lo & piix4_port_mask_sb800) != port)
-		outb_p((smba_en_lo & ~piix4_port_mask_sb800) | port,
-		       SB800_PIIX4_SMB_IDX + 1);
+	prev_port = piix4_sb800_port_sel(adapdata->port, &adapdata->mmio_cfg);
 
 	retval = piix4_access(adap, addr, flags, read_write,
 			      command, size, data);
 
-	outb_p(smba_en_lo, SB800_PIIX4_SMB_IDX + 1);
+	piix4_sb800_port_sel(prev_port, &adapdata->mmio_cfg);
 
 	/* Release the semaphore */
 	outb_p(smbslvcnt | 0x20, SMBSLVCNT);
@@ -758,7 +878,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 		piix4_imc_wakeup();
 
 release:
-	release_region(SB800_PIIX4_SMB_IDX, 2);
+	piix4_sb800_region_release(&adap->dev, &adapdata->mmio_cfg);
 	return retval;
 }
 
@@ -840,6 +960,7 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
 	adapdata->sb800_main = sb800_main;
 	adapdata->port = port << piix4_port_shift_sb800;
 	adapdata->notify_imc = notify_imc;
+	adapdata->mmio_cfg.use_mmio = piix4_sb800_use_mmio(dev);
 
 	/* set up the sysfs linkage to our parent device */
 	adap->dev.parent = &dev->dev;
-- 
2.25.1