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[82.11.51.62]) by smtp.googlemail.com with ESMTPSA id l15-20020a05600c1d0f00b0038c8ff8e708sm6683057wms.13.2022.03.26.03.22.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Mar 2022 03:22:33 -0700 (PDT) From: Lucas Tanure To: Neil Armstrong , Kevin Hilman , Jerome Brunet , Martin Blumenstingl Cc: linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, Lucas Tanure Subject: [PATCH 2/3] i2c: meson: Use 50% duty cycle for I2C clock Date: Sat, 26 Mar 2022 10:22:28 +0000 Message-Id: <20220326102229.421718-3-tanure@linux.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220326102229.421718-1-tanure@linux.com> References: <20220326102229.421718-1-tanure@linux.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220326_032237_193754_26BFD0A0 X-CRM114-Status: GOOD ( 12.72 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org The duty cycle of 33% is less than the required by the I2C specs for the LOW period of the SCL clock. Move the duty cyle to 50% for 100Khz or lower clocks, and (40% High SCL / 60% Low SCL) duty cycle for clocks above 100Khz. Signed-off-by: Lucas Tanure --- drivers/i2c/busses/i2c-meson.c | 45 +++++++++++++++++++++++++--------- 1 file changed, 33 insertions(+), 12 deletions(-) diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c index 4b4a5b2d77ab..b913ba20f06e 100644 --- a/drivers/i2c/busses/i2c-meson.c +++ b/drivers/i2c/busses/i2c-meson.c @@ -140,29 +140,50 @@ static void meson_i2c_add_token(struct meson_i2c *i2c, int token) static void meson_i2c_set_clk_div(struct meson_i2c *i2c, unsigned int freq) { unsigned long clk_rate = clk_get_rate(i2c->clk); - unsigned int div; + unsigned int div_h, div_l; - div = DIV_ROUND_UP(clk_rate, freq); - div -= FILTER_DELAY; - div = DIV_ROUND_UP(div, i2c->data->div_factor); + if (freq <= 100000) { + div_h = DIV_ROUND_UP(clk_rate, freq); + div_l = DIV_ROUND_UP(div_h, 4); + div_h = DIV_ROUND_UP(div_h, 2) - FILTER_DELAY; + } else { + /* According to I2C-BUS Spec 2.1, in FAST-MODE, the minimum LOW period is 1.3uS, and + * minimum HIGH is least 0.6us. + * For 400000 freq, the period is 2.5us. To keep within the specs, give 40% of period to + * HIGH and 60% to LOW. This means HIGH at 1.0us and LOW 1.5us. + * The same applies for Fast-mode plus, where LOW is 0.5us and HIGH is 0.26us. + * Duty = H/(H + L) = 2/5 + */ + div_h = DIV_ROUND_UP(clk_rate * 2, freq * 5) - FILTER_DELAY; + div_l = DIV_ROUND_UP(clk_rate * 3, freq * 5 * 2); + } /* clock divider has 12 bits */ - if (div > GENMASK(11, 0)) { + if (div_h > GENMASK(11, 0)) { dev_err(i2c->dev, "requested bus frequency too low\n"); - div = GENMASK(11, 0); + div_h = GENMASK(11, 0); + } + if (div_l > GENMASK(11, 0)) { + dev_err(i2c->dev, "requested bus frequency too low\n"); + div_l = GENMASK(11, 0); } meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIV_MASK, - FIELD_PREP(REG_CTRL_CLKDIV_MASK, div & GENMASK(9, 0))); + FIELD_PREP(REG_CTRL_CLKDIV_MASK, div_h & GENMASK(9, 0))); meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIVEXT_MASK, - FIELD_PREP(REG_CTRL_CLKDIVEXT_MASK, div >> 10)); + FIELD_PREP(REG_CTRL_CLKDIVEXT_MASK, div_h >> 10)); + + + /* set SCL low delay */ + meson_i2c_set_mask(i2c, REG_SLAVE_ADDR, REG_SLV_SCL_LOW_MASK, + (div_l << REG_SLV_SCL_LOW_SHIFT) & REG_SLV_SCL_LOW_MASK); - /* Disable HIGH/LOW mode */ - meson_i2c_set_mask(i2c, REG_SLAVE_ADDR, REG_SLV_SCL_LOW_EN, 0); + /* Enable HIGH/LOW mode */ + meson_i2c_set_mask(i2c, REG_SLAVE_ADDR, REG_SLV_SCL_LOW_EN, REG_SLV_SCL_LOW_EN); - dev_dbg(i2c->dev, "%s: clk %lu, freq %u, div %u\n", __func__, - clk_rate, freq, div); + dev_dbg(i2c->dev, "%s: clk %lu, freq %u, divh %u, divl %u\n", __func__, + clk_rate, freq, div_h, div_l); } static void meson_i2c_get_data(struct meson_i2c *i2c, char *buf, int len)