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Commit cab9d276 authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Greg Kroah-Hartman
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i2c: uniphier-f: fix violation of tLOW requirement for Fast-mode 



[ Upstream commit ece27a337d42a3197935711997f2880f0957ed7e ]

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: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent eb296b2d

drivers/i2c/busses/i2c-uniphier-f.c

+18 −1
Original line number Diff line number Diff line
@@ -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);