From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.19 68/73] i2c: uniphier: fix violation of tLOW requirement for Fast-mode Date: Wed, 12 Dec 2018 23:28:33 -0500 Message-ID: <20181213042838.75160-68-sashal@kernel.org> References: <20181213042838.75160-1-sashal@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20181213042838.75160-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Masahiro Yamada , Wolfram Sang , Sasha Levin , linux-i2c@vger.kernel.org List-Id: linux-i2c@vger.kernel.org From: Masahiro Yamada [ Upstream commit 8469636ab5d8c77645b953746c10fda6983a8830 ] 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 Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- drivers/i2c/busses/i2c-uniphier.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) 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); } -- 2.19.1