linux-kernel - [PATCH V2 12/18] i2c: imx-lpi2c: fix i2c timing issue

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Message-Id: <20210406113306.2633595-13-xiaoning.wang@nxp.com>
Date:   Tue,  6 Apr 2021 19:33:00 +0800
From:   Clark Wang <xiaoning.wang@....com>
To:     aisheng.dong@....com, robh+dt@...nel.org, shawnguo@...nel.org,
        s.hauer@...gutronix.de, festevam@...il.com
Cc:     kernel@...gutronix.de, linux-imx@....com,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH V2 12/18] i2c: imx-lpi2c: fix i2c timing issue

The clkhi and clklo ratio was not very precise before that can make the
time of START/STOP/HIGH LEVEL out of specification.

Therefore, the calculation of these times has been modified in this patch.
At the same time, the mode rate definition of i2c is corrected.

Signed-off-by: Clark Wang <xiaoning.wang@....com>
Reviewed-by: Fugang Duan <fugang.duan@....com>
---
V2 changes:
 - No change.
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 77dd6ee5a4a8..d124c4000823 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -73,17 +73,17 @@
 #define MCFGR1_IGNACK	BIT(9)
 #define MRDR_RXEMPTY	BIT(14)
 
-#define I2C_CLK_RATIO	2
+#define I2C_CLK_RATIO	24 / 59
 #define CHUNK_DATA	256
 
 #define I2C_PM_TIMEOUT		1000 /* ms */
 
 enum lpi2c_imx_mode {
-	STANDARD,	/* 100+Kbps */
-	FAST,		/* 400+Kbps */
-	FAST_PLUS,	/* 1.0+Mbps */
-	HS,		/* 3.4+Mbps */
-	ULTRA_FAST,	/* 5.0+Mbps */
+	STANDARD,	/* <=100Kbps */
+	FAST,		/* <=400Kbps */
+	FAST_PLUS,	/* <=1.0Mbps */
+	HS,		/* <=3.4Mbps */
+	ULTRA_FAST,	/* <=5.0Mbps */
 };
 
 enum lpi2c_imx_pincfg {
@@ -156,13 +156,13 @@ static void lpi2c_imx_set_mode(struct lpi2c_imx_struct *lpi2c_imx)
 	unsigned int bitrate = lpi2c_imx->bitrate;
 	enum lpi2c_imx_mode mode;
 
-	if (bitrate < I2C_MAX_FAST_MODE_FREQ)
+	if (bitrate <= I2C_MAX_STANDARD_MODE_FREQ)
 		mode = STANDARD;
-	else if (bitrate < I2C_MAX_FAST_MODE_PLUS_FREQ)
+	else if (bitrate <= I2C_MAX_FAST_MODE_FREQ)
 		mode = FAST;
-	else if (bitrate < I2C_MAX_HIGH_SPEED_MODE_FREQ)
+	else if (bitrate <= I2C_MAX_FAST_MODE_PLUS_FREQ)
 		mode = FAST_PLUS;
-	else if (bitrate < I2C_MAX_ULTRA_FAST_MODE_FREQ)
+	else if (bitrate <= I2C_MAX_HIGH_SPEED_MODE_FREQ)
 		mode = HS;
 	else
 		mode = ULTRA_FAST;
@@ -209,7 +209,8 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
 	} while (1);
 }
 
-/* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
+/* CLKLO = (1 - I2C_CLK_RATIO) * clk_cycle, SETHOLD = CLKHI, DATAVD = CLKHI/2
+   CLKHI = I2C_CLK_RATIO * clk_cycle */
 static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
 {
 	u8 prescale, filt, sethold, clkhi, clklo, datavd;
@@ -232,8 +233,8 @@ static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
 
 	for (prescale = 0; prescale <= 7; prescale++) {
 		clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx->bitrate)
-			    - 3 - (filt >> 1);
-		clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
+			    - (2 + filt) / (1 << prescale);
+		clkhi = clk_cycle * I2C_CLK_RATIO;
 		clklo = clk_cycle - clkhi;
 		if (clklo < 64)
 			break;
-- 
2.25.1