1 files changed, 97 insertions, 53 deletions

diff --git a/drivers/i2c/busses/i2c-sh_mobile.c b/drivers/i2c/busses/i2c-sh_mobile.c
index 8110ca45f342..9411c1b892c0 100644
--- a/drivers/i2c/busses/i2c-sh_mobile.c
+++ b/drivers/i2c/busses/i2c-sh_mobile.c
@@ -120,11 +120,12 @@ struct sh_mobile_i2c_data {
 	void __iomem *reg;
 	struct i2c_adapter adap;
 	unsigned long bus_speed;
+	unsigned int clks_per_count;
 	struct clk *clk;
 	u_int8_t icic;
-	u_int8_t iccl;
-	u_int8_t icch;
 	u_int8_t flags;
+	u_int16_t iccl;
+	u_int16_t icch;
 
 	spinlock_t lock;
 	wait_queue_head_t wait;
@@ -135,7 +136,8 @@ struct sh_mobile_i2c_data {
 
 #define IIC_FLAG_HAS_ICIC67	(1 << 0)
 
-#define NORMAL_SPEED		100000 /* FAST_SPEED 400000 */
+#define STANDARD_MODE		100000
+#define FAST_MODE		400000
 
 /* Register offsets */
 #define ICDR			0x00
@@ -187,57 +189,90 @@ static void iic_set_clr(struct sh_mobile_i2c_data *pd, int offs,
 	iic_wr(pd, offs, (iic_rd(pd, offs) | set) & ~clr);
 }
 
-static void activate_ch(struct sh_mobile_i2c_data *pd)
+static u32 sh_mobile_i2c_iccl(unsigned long count_khz, u32 tLOW, u32 tf, int offset)
 {
-	unsigned long i2c_clk;
-	u_int32_t num;
-	u_int32_t denom;
-	u_int32_t tmp;
-
-	/* Wake up device and enable clock */
-	pm_runtime_get_sync(pd->dev);
-	clk_enable(pd->clk);
-
-	/* Get clock rate after clock is enabled */
-	i2c_clk = clk_get_rate(pd->clk);
+	/*
+	 * Conditional expression:
+	 *   ICCL >= COUNT_CLK * (tLOW + tf)
+	 *
+	 * SH-Mobile IIC hardware starts counting the LOW period of
+	 * the SCL signal (tLOW) as soon as it pulls the SCL line.
+	 * In order to meet the tLOW timing spec, we need to take into
+	 * account the fall time of SCL signal (tf).  Default tf value
+	 * should be 0.3 us, for safety.
+	 */
+	return (((count_khz * (tLOW + tf)) + 5000) / 10000) + offset;
+}
 
-	/* Calculate the value for iccl. From the data sheet:
-	 * iccl = (p clock / transfer rate) * (L / (L + H))
-	 * where L and H are the SCL low/high ratio (5/4 in this case).
-	 * We also round off the result.
+static u32 sh_mobile_i2c_icch(unsigned long count_khz, u32 tHIGH, u32 tf, int offset)
+{
+	/*
+	 * Conditional expression:
+	 *   ICCH >= COUNT_CLK * (tHIGH + tf)
+	 *
+	 * SH-Mobile IIC hardware is aware of SCL transition period 'tr',
+	 * and can ignore it.  SH-Mobile IIC controller starts counting
+	 * the HIGH period of the SCL signal (tHIGH) after the SCL input
+	 * voltage increases at VIH.
+	 *
+	 * Afterward it turned out calculating ICCH using only tHIGH spec
+	 * will result in violation of the tHD;STA timing spec.  We need
+	 * to take into account the fall time of SDA signal (tf) at START
+	 * condition, in order to meet both tHIGH and tHD;STA specs.
 	 */
-	num = i2c_clk * 5;
-	denom = pd->bus_speed * 9;
-	tmp = num * 10 / denom;
-	if (tmp % 10 >= 5)
-		pd->iccl = (u_int8_t)((num/denom) + 1);
-	else
-		pd->iccl = (u_int8_t)(num/denom);
+	return (((count_khz * (tHIGH + tf)) + 5000) / 10000) + offset;
+}
 
-	/* one more bit of ICCL in ICIC */
-	if (pd->flags & IIC_FLAG_HAS_ICIC67) {
-		if ((num/denom) > 0xff)
-			pd->icic |= ICIC_ICCLB8;
-		else
-			pd->icic &= ~ICIC_ICCLB8;
+static void sh_mobile_i2c_init(struct sh_mobile_i2c_data *pd)
+{
+	unsigned long i2c_clk_khz;
+	u32 tHIGH, tLOW, tf;
+	int offset;
+
+	/* Get clock rate after clock is enabled */
+	clk_enable(pd->clk);
+	i2c_clk_khz = clk_get_rate(pd->clk) / 1000;
+	i2c_clk_khz /= pd->clks_per_count;
+
+	if (pd->bus_speed == STANDARD_MODE) {
+		tLOW	= 47;	/* tLOW = 4.7 us */
+		tHIGH	= 40;	/* tHD;STA = tHIGH = 4.0 us */
+		tf	= 3;	/* tf = 0.3 us */
+		offset	= 0;	/* No offset */
+	} else if (pd->bus_speed == FAST_MODE) {
+		tLOW	= 13;	/* tLOW = 1.3 us */
+		tHIGH	= 6;	/* tHD;STA = tHIGH = 0.6 us */
+		tf	= 3;	/* tf = 0.3 us */
+		offset	= 0;	/* No offset */
+	} else {
+		dev_err(pd->dev, "unrecognized bus speed %lu Hz\n",
+			pd->bus_speed);
+		goto out;
 	}
 
-	/* Calculate the value for icch. From the data sheet:
-	   icch = (p clock / transfer rate) * (H / (L + H)) */
-	num = i2c_clk * 4;
-	tmp = num * 10 / denom;
-	if (tmp % 10 >= 5)
-		pd->icch = (u_int8_t)((num/denom) + 1);
+	pd->iccl = sh_mobile_i2c_iccl(i2c_clk_khz, tLOW, tf, offset);
+	/* one more bit of ICCL in ICIC */
+	if ((pd->iccl > 0xff) && (pd->flags & IIC_FLAG_HAS_ICIC67))
+		pd->icic |= ICIC_ICCLB8;
 	else
-		pd->icch = (u_int8_t)(num/denom);
+		pd->icic &= ~ICIC_ICCLB8;
 
+	pd->icch = sh_mobile_i2c_icch(i2c_clk_khz, tHIGH, tf, offset);
 	/* one more bit of ICCH in ICIC */
-	if (pd->flags & IIC_FLAG_HAS_ICIC67) {
-		if ((num/denom) > 0xff)
-			pd->icic |= ICIC_ICCHB8;
-		else
-			pd->icic &= ~ICIC_ICCHB8;
-	}
+	if ((pd->icch > 0xff) && (pd->flags & IIC_FLAG_HAS_ICIC67))
+		pd->icic |= ICIC_ICCHB8;
+	else
+		pd->icic &= ~ICIC_ICCHB8;
+
+out:
+	clk_disable(pd->clk);
+}
+
+static void activate_ch(struct sh_mobile_i2c_data *pd)
+{
+	/* Wake up device and enable clock */
+	pm_runtime_get_sync(pd->dev);
+	clk_enable(pd->clk);
 
 	/* Enable channel and configure rx ack */
 	iic_set_clr(pd, ICCR, ICCR_ICE, 0);
@@ -246,8 +281,8 @@ static void activate_ch(struct sh_mobile_i2c_data *pd)
 	iic_wr(pd, ICIC, 0);
 
 	/* Set the clock */
-	iic_wr(pd, ICCL, pd->iccl);
-	iic_wr(pd, ICCH, pd->icch);
+	iic_wr(pd, ICCL, pd->iccl & 0xff);
+	iic_wr(pd, ICCH, pd->icch & 0xff);
 }
 
 static void deactivate_ch(struct sh_mobile_i2c_data *pd)
@@ -434,6 +469,9 @@ static irqreturn_t sh_mobile_i2c_isr(int irq, void *dev_id)
 		wake_up(&pd->wait);
 	}
 
+	/* defeat write posting to avoid spurious WAIT interrupts */
+	iic_rd(pd, ICSR);
+
 	return IRQ_HANDLED;
 }
 
@@ -451,8 +489,8 @@ static int start_ch(struct sh_mobile_i2c_data *pd, struct i2c_msg *usr_msg)
 	iic_set_clr(pd, ICCR, ICCR_ICE, 0);
 
 	/* Set the clock */
-	iic_wr(pd, ICCL, pd->iccl);
-	iic_wr(pd, ICCH, pd->icch);
+	iic_wr(pd, ICCL, pd->iccl & 0xff);
+	iic_wr(pd, ICCH, pd->icch & 0xff);
 
 	pd->msg = usr_msg;
 	pd->pos = -1;
@@ -621,10 +659,13 @@ static int sh_mobile_i2c_probe(struct platform_device *dev)
 		goto err_irq;
 	}
 
-	/* Use platformd data bus speed or NORMAL_SPEED */
-	pd->bus_speed = NORMAL_SPEED;
+	/* Use platform data bus speed or STANDARD_MODE */
+	pd->bus_speed = STANDARD_MODE;
 	if (pdata && pdata->bus_speed)
 		pd->bus_speed = pdata->bus_speed;
+	pd->clks_per_count = 1;
+	if (pdata && pdata->clks_per_count)
+		pd->clks_per_count = pdata->clks_per_count;
 
 	/* The IIC blocks on SH-Mobile ARM processors
 	 * come with two new bits in ICIC.
@@ -632,6 +673,8 @@ static int sh_mobile_i2c_probe(struct platform_device *dev)
 	if (size > 0x17)
 		pd->flags |= IIC_FLAG_HAS_ICIC67;
 
+	sh_mobile_i2c_init(pd);
+
 	/* Enable Runtime PM for this device.
 	 *
 	 * Also tell the Runtime PM core to ignore children
@@ -667,8 +710,9 @@ static int sh_mobile_i2c_probe(struct platform_device *dev)
 		goto err_all;
 	}
 
-	dev_info(&dev->dev, "I2C adapter %d with bus speed %lu Hz\n",
-		 adap->nr, pd->bus_speed);
+	dev_info(&dev->dev,
+		 "I2C adapter %d with bus speed %lu Hz (L/H=%x/%x)\n",
+		 adap->nr, pd->bus_speed, pd->iccl, pd->icch);
 
 	of_i2c_register_devices(adap);
 	return 0;