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authorMasahiro Yamada <yamada.masahiro@socionext.com>2018-12-06 12:55:27 +0900
committerWolfram Sang <wsa@the-dreams.de>2018-12-06 23:14:59 +0100
commit8469636ab5d8c77645b953746c10fda6983a8830 (patch)
treebb912f98a8108830ea93d2c7949a4ed1e7518194 /drivers
parentcd8843f541cc0ef057e27f1afba46374bbb84219 (diff)
i2c: uniphier: 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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/i2c/busses/i2c-uniphier.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-uniphier.c b/drivers/i2c/busses/i2c-uniphier.c
index 454f914ae66d..c488e558aef7 100644
--- a/drivers/i2c/busses/i2c-uniphier.c
+++ b/drivers/i2c/busses/i2c-uniphier.c
@@ -320,7 +320,13 @@ static void uniphier_i2c_hw_init(struct uniphier_i2c_priv *priv)
uniphier_i2c_reset(priv, true);
- writel((cyc / 2 << 16) | cyc, priv->membase + UNIPHIER_I2C_CLK);
+ /*
+ * Bit30-16: clock cycles of tLOW.
+ * Standard-mode: tLOW = 4.7 us, tHIGH = 4.0 us
+ * Fast-mode: tLOW = 1.3 us, tHIGH = 0.6 us
+ * "tLow/tHIGH = 5/4" meets both.
+ */
+ writel((cyc * 5 / 9 << 16) | cyc, priv->membase + UNIPHIER_I2C_CLK);
uniphier_i2c_reset(priv, false);
}