From 54c76ed33008d0b342daa52a45ac304e5e3ab312 Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Thu, 21 Sep 2023 14:53:50 +0200 Subject: i2c: rcar: improve accuracy for R-Car Gen3+ With some new registers, SCL can be calculated to be closer to the desired rate. Apply the new formula for R-Car Gen3 device types. Signed-off-by: Wolfram Sang Reviewed-by: Geert Uytterhoeven Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-rcar.c | 128 +++++++++++++++++++++++++++++------------- 1 file changed, 89 insertions(+), 39 deletions(-) (limited to 'drivers/i2c/busses/i2c-rcar.c') diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 6800059514bc..8417d5bc662b 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -41,6 +41,10 @@ #define ICSAR 0x1C /* slave address */ #define ICMAR 0x20 /* master address */ #define ICRXTX 0x24 /* data port */ +#define ICCCR2 0x28 /* Clock control 2 */ +#define ICMPR 0x2C /* SCL mask control */ +#define ICHPR 0x30 /* SCL HIGH control */ +#define ICLPR 0x34 /* SCL LOW control */ #define ICFBSCR 0x38 /* first bit setup cycle (Gen3) */ #define ICDMAER 0x3c /* DMA enable (Gen3) */ @@ -84,11 +88,25 @@ #define RMDMAE BIT(1) /* DMA Master Received Enable */ #define TMDMAE BIT(0) /* DMA Master Transmitted Enable */ +/* ICCCR2 */ +#define CDFD BIT(2) /* CDF Disable */ +#define HLSE BIT(1) /* HIGH/LOW Separate Control Enable */ +#define SME BIT(0) /* SCL Mask Enable */ + /* ICFBSCR */ #define TCYC17 0x0f /* 17*Tcyc delay 1st bit between SDA and SCL */ #define RCAR_MIN_DMA_LEN 8 +/* SCL low/high ratio 5:4 to meet all I2C timing specs (incl safety margin) */ +#define RCAR_SCLD_RATIO 5 +#define RCAR_SCHD_RATIO 4 +/* + * SMD should be smaller than SCLD/SCHD and is always around 20 in the docs. + * Thus, we simply use 20 which works for low and high speeds. + */ +#define RCAR_DEFAULT_SMD 20 + #define RCAR_BUS_PHASE_START (MDBS | MIE | ESG) #define RCAR_BUS_PHASE_DATA (MDBS | MIE) #define RCAR_BUS_PHASE_STOP (MDBS | MIE | FSB) @@ -128,6 +146,8 @@ struct rcar_i2c_priv { int pos; u32 icccr; + u16 schd; + u16 scld; u8 recovery_icmcr; /* protected by adapter lock */ enum rcar_i2c_type devtype; struct i2c_client *slave; @@ -216,11 +236,16 @@ static void rcar_i2c_init(struct rcar_i2c_priv *priv) rcar_i2c_write(priv, ICMCR, MDBS); rcar_i2c_write(priv, ICMSR, 0); /* start clock */ - rcar_i2c_write(priv, ICCCR, priv->icccr); - - if (priv->devtype == I2C_RCAR_GEN3) + if (priv->devtype < I2C_RCAR_GEN3) { + rcar_i2c_write(priv, ICCCR, priv->icccr); + } else { + rcar_i2c_write(priv, ICCCR2, CDFD | HLSE | SME); + rcar_i2c_write(priv, ICCCR, priv->icccr); + rcar_i2c_write(priv, ICMPR, RCAR_DEFAULT_SMD); + rcar_i2c_write(priv, ICHPR, priv->schd); + rcar_i2c_write(priv, ICLPR, priv->scld); rcar_i2c_write(priv, ICFBSCR, TCYC17); - + } } static int rcar_i2c_bus_barrier(struct rcar_i2c_priv *priv) @@ -241,7 +266,7 @@ static int rcar_i2c_bus_barrier(struct rcar_i2c_priv *priv) static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv) { - u32 scgd, cdf, round, ick, sum, scl, cdf_width; + u32 cdf, round, ick, sum, scl, cdf_width; unsigned long rate; struct device *dev = rcar_i2c_priv_to_dev(priv); struct i2c_timings t = { @@ -254,27 +279,17 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv) /* Fall back to previously used values if not supplied */ i2c_parse_fw_timings(dev, &t, false); - switch (priv->devtype) { - case I2C_RCAR_GEN1: - cdf_width = 2; - break; - case I2C_RCAR_GEN2: - case I2C_RCAR_GEN3: - cdf_width = 3; - break; - default: - dev_err(dev, "device type error\n"); - return -EIO; - } - /* * calculate SCL clock * see - * ICCCR + * ICCCR (and ICCCR2 for Gen3+) * * ick = clkp / (1 + CDF) * SCL = ick / (20 + SCGD * 8 + F[(ticf + tr + intd) * ick]) * + * for Gen3+: + * SCL = clkp / (8 + SMD * 2 + SCLD + SCHD +F[(ticf + tr + intd) * clkp]) + * * ick : I2C internal clock < 20 MHz * ticf : I2C SCL falling time * tr : I2C SCL rising time @@ -284,11 +299,12 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv) */ rate = clk_get_rate(priv->clk); cdf = rate / 20000000; - if (cdf >= 1U << cdf_width) { - dev_err(dev, "Input clock %lu too high\n", rate); - return -EIO; - } - ick = rate / (cdf + 1); + cdf_width = (priv->devtype == I2C_RCAR_GEN1) ? 2 : 3; + if (cdf >= 1U << cdf_width) + goto err_no_val; + + /* On Gen3+, we use cdf only for the filters, not as a SCL divider */ + ick = rate / (priv->devtype < I2C_RCAR_GEN3 ? (cdf + 1) : 1); /* * It is impossible to calculate a large scale number on u32. Separate it. @@ -301,24 +317,58 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv) round = DIV_ROUND_CLOSEST(ick, 1000000); round = DIV_ROUND_CLOSEST(round * sum, 1000); - /* - * SCL = ick / (20 + 8 * SCGD + F[(ticf + tr + intd) * ick]) - * 20 + 8 * SCGD + F[...] = ick / SCL - * SCGD = ((ick / SCL) - 20 - F[...]) / 8 - * Result (= SCL) should be less than bus_speed for hardware safety - */ - scgd = DIV_ROUND_UP(ick, t.bus_freq_hz ?: 1); - scgd = DIV_ROUND_UP(scgd - 20 - round, 8); - scl = ick / (20 + 8 * scgd + round); + if (priv->devtype < I2C_RCAR_GEN3) { + u32 scgd; + /* + * SCL = ick / (20 + 8 * SCGD + F[(ticf + tr + intd) * ick]) + * 20 + 8 * SCGD + F[...] = ick / SCL + * SCGD = ((ick / SCL) - 20 - F[...]) / 8 + * Result (= SCL) should be less than bus_speed for hardware safety + */ + scgd = DIV_ROUND_UP(ick, t.bus_freq_hz ?: 1); + scgd = DIV_ROUND_UP(scgd - 20 - round, 8); + scl = ick / (20 + 8 * scgd + round); - if (scgd > 0x3f) - goto err_no_val; + if (scgd > 0x3f) + goto err_no_val; - dev_dbg(dev, "clk %u/%u(%lu), round %u, CDF: %u, SCGD: %u\n", - scl, t.bus_freq_hz, rate, round, cdf, scgd); + dev_dbg(dev, "clk %u/%u(%lu), round %u, CDF: %u, SCGD: %u\n", + scl, t.bus_freq_hz, rate, round, cdf, scgd); - /* keep icccr value */ - priv->icccr = scgd << cdf_width | cdf; + priv->icccr = scgd << cdf_width | cdf; + } else { + u32 x, sum_ratio = RCAR_SCHD_RATIO + RCAR_SCLD_RATIO; + /* + * SCLD/SCHD ratio and SMD default value are explained above + * where they are defined. With these definitions, we can compute + * x as a base value for the SCLD/SCHD ratio: + * + * SCL = clkp / (8 + 2 * SMD + SCLD + SCHD + F[(ticf + tr + intd) * clkp]) + * SCL = clkp / (8 + 2 * RCAR_DEFAULT_SMD + RCAR_SCLD_RATIO * x + * + RCAR_SCHD_RATIO * x + F[...]) + * + * with: sum_ratio = RCAR_SCLD_RATIO + RCAR_SCHD_RATIO + * and: smd = RCAR_DEFAULT_SMD + * + * SCL = clkp / (8 + 2 * smd + sum_ratio * x + F[...]) + * 8 + 2 * smd + sum_ratio * x + F[...] = clkp / SCL + * x = ((clkp / SCL) - 8 - 2 * smd - F[...]) / sum_ratio + */ + x = DIV_ROUND_UP(rate, t.bus_freq_hz ?: 1); + x = DIV_ROUND_UP(x - 8 - 2 * RCAR_DEFAULT_SMD - round, sum_ratio); + scl = rate / (8 + 2 * RCAR_DEFAULT_SMD + sum_ratio * x + round); + + /* Bail out if values don't fit into 16 bit or SMD became too large */ + if (x * RCAR_SCLD_RATIO > 0xffff || RCAR_DEFAULT_SMD > x * RCAR_SCHD_RATIO) + goto err_no_val; + + priv->icccr = cdf; + priv->schd = RCAR_SCHD_RATIO * x; + priv->scld = RCAR_SCLD_RATIO * x; + + dev_dbg(dev, "clk %u/%u(%lu), round %u, CDF: %u SCHD %u SCLD %u\n", + scl, t.bus_freq_hz, rate, round, cdf, priv->schd, priv->scld); + } return 0; -- cgit v1.2.3-70-g09d2