diff options
| author | Masahiro Yamada <yamada.masahiro@socionext.com> | 2018-12-06 06:55:27 +0300 |
|---|---|---|
| committer | Wolfram Sang <wsa@the-dreams.de> | 2018-12-07 01:14:59 +0300 |
| commit | 8469636ab5d8c77645b953746c10fda6983a8830 (patch) | |
| tree | bb912f98a8108830ea93d2c7949a4ed1e7518194 /drivers | |
| parent | cd8843f541cc0ef057e27f1afba46374bbb84219 (diff) | |
| download | linux-8469636ab5d8c77645b953746c10fda6983a8830.tar.xz | |
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.c | 8 |
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); } |