i2c: uniphier-f: fix violation of tLOW requirement for Fast-mode

Currently, the clock duty is set as tLOW/tHIGH = 1/1. For Fast-mode,
tLOW is set to 1.25 us while the I2C spec requires tLOW >= 1.3 us.

tLOW/tHIGH = 5/4 would meet both Standard-mode and Fast-mode:
  Standard-mode: tLOW = 5.56 us, tHIGH = 4.44 us
  Fast-mode:     tLOW = 1.39 us, tHIGH = 1.11 us

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-uniphier-f.c b/drivers/i2c/busses/i2c-uniphier-f.c
index d8a5db1..03da4a5 100644 (file)
--- a/drivers/i2c/busses/i2c-uniphier-f.c
+++ b/drivers/i2c/busses/i2c-uniphier-f.c
@@ -518,9 +518,26 @@ static void uniphier_fi2c_hw_init(struct uniphier_fi2c_priv *priv)
 
        uniphier_fi2c_reset(priv);
 
+       /*
+        *  Standard-mode: tLOW + tHIGH = 10 us
+        *  Fast-mode:     tLOW + tHIGH = 2.5 us
+        */
        writel(cyc, priv->membase + UNIPHIER_FI2C_CYC);
-       writel(cyc / 2, priv->membase + UNIPHIER_FI2C_LCTL);
+       /*
+        *  Standard-mode: tLOW = 4.7 us, tHIGH = 4.0 us, tBUF = 4.7 us
+        *  Fast-mode:     tLOW = 1.3 us, tHIGH = 0.6 us, tBUF = 1.3 us
+        * "tLow/tHIGH = 5/4" meets both.
+        */
+       writel(cyc * 5 / 9, priv->membase + UNIPHIER_FI2C_LCTL);
+       /*
+        *  Standard-mode: tHD;STA = 4.0 us, tSU;STA = 4.7 us, tSU;STO = 4.0 us
+        *  Fast-mode:     tHD;STA = 0.6 us, tSU;STA = 0.6 us, tSU;STO = 0.6 us
+        */
        writel(cyc / 2, priv->membase + UNIPHIER_FI2C_SSUT);
+       /*
+        *  Standard-mode: tSU;DAT = 250 ns
+        *  Fast-mode:     tSU;DAT = 100 ns
+        */
        writel(cyc / 16, priv->membase + UNIPHIER_FI2C_DSUT);
 
        uniphier_fi2c_prepare_operation(priv);