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

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[ Upstream commit ece27a337d ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Masahiro Yamada 2018-12-06 12:55:28 +09:00 committed by Greg Kroah-Hartman
parent eb296b2d31
commit cab9d27671
1 changed files with 18 additions and 1 deletions
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19
drivers/i2c/busses/i2c-uniphier-f.c
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@ -470,9 +470,26 @@ 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);