From 2263e9b8817235223a56a99681b114f640dfc491 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ky=C3=B6sti=20M=C3=A4lkki?= Date: Wed, 28 Apr 2021 09:13:21 +0300 Subject: drivers/i2c/designware: Use safe defaults for SCL parameters MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Inspired by discussion in CB:22822. If I2C bus step response has not been measured, assume the layout to have been designed with a minimal capacitance and SCL rise and fall times of 0 ns. The calculations will add the required amount of reference clocks for the host to drive SCL high or low, such that the maximum bus frequency specification is met. Change-Id: Icbafae22c83ffbc16c179fb5412fb4fd6b70813a Signed-off-by: Kyösti Mälkki Reviewed-on: https://review.coreboot.org/c/coreboot/+/52723 Reviewed-by: Tim Wawrzynczak Reviewed-by: Furquan Shaikh Reviewed-by: Werner Zeh Tested-by: build bot (Jenkins) --- src/drivers/i2c/designware/dw_i2c.c | 32 ++------------------------------ 1 file changed, 2 insertions(+), 30 deletions(-) (limited to 'src/drivers/i2c') diff --git a/src/drivers/i2c/designware/dw_i2c.c b/src/drivers/i2c/designware/dw_i2c.c index c0212c3e27..2e2d20d78c 100644 --- a/src/drivers/i2c/designware/dw_i2c.c +++ b/src/drivers/i2c/designware/dw_i2c.c @@ -621,7 +621,6 @@ int dw_i2c_gen_speed_config(uintptr_t dw_i2c_addr, { const int ic_clk = CONFIG_DRIVERS_I2C_DESIGNWARE_CLOCK_MHZ; struct dw_i2c_regs *regs; - uint16_t hcnt_min, lcnt_min; int i; regs = (struct dw_i2c_regs *)dw_i2c_addr; @@ -637,35 +636,8 @@ int dw_i2c_gen_speed_config(uintptr_t dw_i2c_addr, return 0; } - /* If rise time is set use the time calculation. */ - if (bcfg->rise_time_ns) - return dw_i2c_gen_config_rise_fall_time(regs, speed, bcfg, - ic_clk, config); - - if (speed >= I2C_SPEED_HIGH) { - /* High speed */ - hcnt_min = MIN_HS_SCL_HIGHTIME; - lcnt_min = MIN_HS_SCL_LOWTIME; - } else if (speed >= I2C_SPEED_FAST_PLUS) { - /* Fast-Plus speed */ - hcnt_min = MIN_FP_SCL_HIGHTIME; - lcnt_min = MIN_FP_SCL_LOWTIME; - } else if (speed >= I2C_SPEED_FAST) { - /* Fast speed */ - hcnt_min = MIN_FS_SCL_HIGHTIME; - lcnt_min = MIN_FS_SCL_LOWTIME; - } else { - /* Standard speed */ - hcnt_min = MIN_SS_SCL_HIGHTIME; - lcnt_min = MIN_SS_SCL_LOWTIME; - } - - config->speed = speed; - config->scl_hcnt = ic_clk * hcnt_min / KHz; - config->scl_lcnt = ic_clk * lcnt_min / KHz; - config->sda_hold = ic_clk * DEFAULT_SDA_HOLD_TIME / KHz; - - return 0; + /* Use the time calculation. */ + return dw_i2c_gen_config_rise_fall_time(regs, speed, bcfg, ic_clk, config); } static int dw_i2c_set_speed(unsigned int bus, enum i2c_speed speed, -- cgit v1.2.3