i2c: thunderx: Support for High speed mode

To support bus operations for high speed bus frequencies greater than
400KHZ following control bits need to be setup accordingly
 - hs_mode (bit 0) field in Mode register to switch controller
   between low-speed and high-speed frequency operating mode.
 - Setup clock divisors for desired TWSI bus frequency using
   FOSCL output frequency divisor (D):
   0 - sets the divisor to 10 for low speed mode
   1 - sets the divisor to 15 for high speed mode.
The TWSI bus output frequency, in master mode is based on:
                TCLK = 100MHz / (THP + 2)
                FOSCL = FSAMP / (M+1)×D = TCLK / (2 ^ N × (M + 1) × 15)
                FSAMP = TCLK / 2 ^ N
where,
        N is <2:0> and M is <6:3> of TWSI Clock Control Register
        D is 10 for low speed or 15 for HS_MODE

With high speed mode support, HLC mode usage is limited to
low speed frequency (<=400KHz) bus transfers in hardware.

Signed-off-by: Suneel Garapati <sgarapati@marvell.com>
Signed-off-by: Piyush Malgujar <pmalgujar@marvell.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Author: Suneel Garapati

drivers/i2c/busses/i2c-octeon-core.c

@@ -612,25 +612,27 @@ int octeon_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	struct octeon_i2c *i2c = i2c_get_adapdata(adap);
 	int i, ret = 0;
 
-	if (num == 1) {
-		if (msgs[0].len > 0 && msgs[0].len <= 8) {
-			if (msgs[0].flags & I2C_M_RD)
-				ret = octeon_i2c_hlc_read(i2c, msgs);
-			else
-				ret = octeon_i2c_hlc_write(i2c, msgs);
-			goto out;
-		}
-	} else if (num == 2) {
-		if ((msgs[0].flags & I2C_M_RD) == 0 &&
-		    (msgs[1].flags & I2C_M_RECV_LEN) == 0 &&
-		    msgs[0].len > 0 && msgs[0].len <= 2 &&
-		    msgs[1].len > 0 && msgs[1].len <= 8 &&
-		    msgs[0].addr == msgs[1].addr) {
-			if (msgs[1].flags & I2C_M_RD)
-				ret = octeon_i2c_hlc_comp_read(i2c, msgs);
-			else
-				ret = octeon_i2c_hlc_comp_write(i2c, msgs);
-			goto out;
+	if (IS_LS_FREQ(i2c->twsi_freq)) {
+		if (num == 1) {
+			if (msgs[0].len > 0 && msgs[0].len <= 8) {
+				if (msgs[0].flags & I2C_M_RD)
+					ret = octeon_i2c_hlc_read(i2c, msgs);
+				else
+					ret = octeon_i2c_hlc_write(i2c, msgs);
+				goto out;
+			}
+		} else if (num == 2) {
+			if ((msgs[0].flags & I2C_M_RD) == 0 &&
+			    (msgs[1].flags & I2C_M_RECV_LEN) == 0 &&
+			    msgs[0].len > 0 && msgs[0].len <= 2 &&
+			    msgs[1].len > 0 && msgs[1].len <= 8 &&
+			    msgs[0].addr == msgs[1].addr) {
+				if (msgs[1].flags & I2C_M_RD)
+					ret = octeon_i2c_hlc_comp_read(i2c, msgs);
+				else
+					ret = octeon_i2c_hlc_comp_write(i2c, msgs);
+				goto out;
+			}
 		}
 	}
 
@@ -664,19 +666,24 @@ void octeon_i2c_set_clock(struct octeon_i2c *i2c)
 {
 	int tclk, thp_base, inc, thp_idx, mdiv_idx, ndiv_idx, foscl, diff;
 	bool is_plat_otx2;
-	unsigned int mdiv_min = 2;
 	/*
 	 * Find divisors to produce target frequency, start with large delta
-	 * to cover wider range of divisors, note thp = TCLK half period.
+	 * to cover wider range of divisors, note thp = TCLK half period and
+	 * ds is OSCL output frequency divisor.
 	 */
-	unsigned int thp = TWSI_MASTER_CLK_REG_DEF_VAL, mdiv = 2, ndiv = 0;
+	unsigned int thp, mdiv_min, mdiv = 2, ndiv = 0, ds = 10;
 	unsigned int delta_hz = INITIAL_DELTA_HZ;
 
 	is_plat_otx2 = octeon_i2c_is_otx2(to_pci_dev(i2c->dev));
 
 	if (is_plat_otx2) {
 		thp = TWSI_MASTER_CLK_REG_OTX2_VAL;
 		mdiv_min = 0;
+		if (!IS_LS_FREQ(i2c->twsi_freq))
+			ds = 15;
+	} else {
+		thp = TWSI_MASTER_CLK_REG_DEF_VAL;
+		mdiv_min = 2;
 	}
 
 	for (ndiv_idx = 0; ndiv_idx < 8 && delta_hz != 0; ndiv_idx++) {
@@ -689,7 +696,7 @@ void octeon_i2c_set_clock(struct octeon_i2c *i2c)
 			 * For given ndiv and mdiv values check the
 			 * two closest thp values.
 			 */
-			tclk = i2c->twsi_freq * (mdiv_idx + 1) * 10;
+			tclk = i2c->twsi_freq * (mdiv_idx + 1) * ds;
 			tclk *= (1 << ndiv_idx);
 			if (is_plat_otx2)
 				thp_base = (i2c->sys_freq / tclk) - 2;
@@ -707,7 +714,9 @@ void octeon_i2c_set_clock(struct octeon_i2c *i2c)
 					foscl = i2c->sys_freq /
 						(2 * (thp_idx + 1));
 				foscl = foscl / (1 << ndiv_idx);
-				foscl = foscl / (mdiv_idx + 1) / 10;
+				foscl = foscl / (mdiv_idx + 1) / ds;
+				if (foscl > i2c->twsi_freq)
+					continue;
 				diff = abs(foscl - i2c->twsi_freq);
 				/*
 				 * Diff holds difference between calculated frequency
@@ -725,6 +734,17 @@ void octeon_i2c_set_clock(struct octeon_i2c *i2c)
 	}
 	octeon_i2c_reg_write(i2c, SW_TWSI_OP_TWSI_CLK, thp);
 	octeon_i2c_reg_write(i2c, SW_TWSI_EOP_TWSI_CLKCTL, (mdiv << 3) | ndiv);
+	if (is_plat_otx2) {
+		u64 mode;
+
+		mode = __raw_readq(i2c->twsi_base + MODE(i2c));
+		/* Set REFCLK_SRC and HS_MODE in TWSX_MODE register */
+		if (!IS_LS_FREQ(i2c->twsi_freq))
+			mode |= TWSX_MODE_HS_MASK;
+		else
+			mode &= ~TWSX_MODE_HS_MASK;
+		octeon_i2c_writeq_flush(mode, i2c->twsi_base + MODE(i2c));
+	}
 }
 
 int octeon_i2c_init_lowlevel(struct octeon_i2c *i2c)

drivers/i2c/busses/i2c-octeon-core.h

@@ -94,11 +94,18 @@ struct octeon_i2c_reg_offset {
 	unsigned int sw_twsi;
 	unsigned int twsi_int;
 	unsigned int sw_twsi_ext;
+	unsigned int mode;
 };
 
 #define SW_TWSI(x)	(x->roff.sw_twsi)
 #define TWSI_INT(x)	(x->roff.twsi_int)
 #define SW_TWSI_EXT(x)	(x->roff.sw_twsi_ext)
+#define MODE(x)		((x)->roff.mode)
+
+/* Set REFCLK_SRC and HS_MODE in TWSX_MODE register */
+#define TWSX_MODE_REFCLK_SRC	BIT(4)
+#define TWSX_MODE_HS_MODE	BIT(0)
+#define TWSX_MODE_HS_MASK	(TWSX_MODE_REFCLK_SRC | TWSX_MODE_HS_MODE)
 
 struct octeon_i2c {
 	wait_queue_head_t queue;
@@ -213,6 +220,7 @@ static inline void octeon_i2c_write_int(struct octeon_i2c *i2c, u64 data)
 	octeon_i2c_writeq_flush(data, i2c->twsi_base + TWSI_INT(i2c));
 }
 
+#define IS_LS_FREQ(twsi_freq)	((twsi_freq) <= 400000)
 #define PCI_SUBSYS_DEVID_9XXX	0xB
 #define PCI_SUBSYS_MASK		GENMASK(15, 12)
 /**

drivers/i2c/busses/i2c-thunderx-pcidrv.c

@@ -166,6 +166,7 @@ static int thunder_i2c_probe_pci(struct pci_dev *pdev,
 	i2c->roff.sw_twsi = 0x1000;
 	i2c->roff.twsi_int = 0x1010;
 	i2c->roff.sw_twsi_ext = 0x1018;
+	i2c->roff.mode = 0x1038;
 
 	i2c->dev = dev;
 	pci_set_drvdata(pdev, i2c);
@@ -210,7 +211,7 @@ static int thunder_i2c_probe_pci(struct pci_dev *pdev,
 	 * For OcteonTX2 chips, set reference frequency to 100MHz
 	 * as refclk_src in TWSI_MODE register defaults to 100MHz.
 	 */
-	if (octeon_i2c_is_otx2(pdev))
+	if (octeon_i2c_is_otx2(pdev) && IS_LS_FREQ(i2c->twsi_freq))
 		i2c->sys_freq = OTX2_REF_FREQ_DEFAULT;
 	octeon_i2c_set_clock(i2c);