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driver: i2c: npcx: adjust parameters for better I2C timing at 100 KHz

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The original parameter (k1) setting may let the I2C frequency be a
little bit higher than 100k Hz, which causes the timing Tsu:sta (set-up
time for a repeated START) to violate the spec. This change fixes the k1
parameter and also changes the HLDT to the suggested value in the
datasheet.

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>
This commit is contained in:
Jun Lin 2021-12-15 09:59:06 +08:00 committed by Maureen Helm
parent 7a68fff753
commit f7c2f4fd94
1 changed files with 6 additions and 4 deletions
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10
drivers/i2c/i2c_npcx_controller.c
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@ -161,13 +161,13 @@ struct i2c_ctrl_data {
/* Recommended I2C timing values are based on 15 MHz */
static const struct npcx_i2c_timing_cfg npcx_15m_speed_confs[] = {
[NPCX_I2C_BUS_SPEED_100KHZ] = {.HLDT = 0, .k1 = 75, .k2 = 0},
[NPCX_I2C_BUS_SPEED_100KHZ] = {.HLDT = 15, .k1 = 76, .k2 = 0},
[NPCX_I2C_BUS_SPEED_400KHZ] = {.HLDT = 7, .k1 = 24, .k2 = 18,},
[NPCX_I2C_BUS_SPEED_1MHZ] = {.HLDT = 7, .k1 = 14, .k2 = 10,},
};
static const struct npcx_i2c_timing_cfg npcx_20m_speed_confs[] = {
[NPCX_I2C_BUS_SPEED_100KHZ] = {.HLDT = 0, .k1 = 100, .k2 = 0},
[NPCX_I2C_BUS_SPEED_100KHZ] = {.HLDT = 15, .k1 = 102, .k2 = 0},
[NPCX_I2C_BUS_SPEED_400KHZ] = {.HLDT = 7, .k1 = 32, .k2 = 22},
[NPCX_I2C_BUS_SPEED_1MHZ] = {.HLDT = 7, .k1 = 16, .k2 = 10},
};
@ -349,11 +349,13 @@ static void i2c_ctrl_config_bus_freq(const struct device *dev,
if (bus_freq == NPCX_I2C_BUS_SPEED_100KHZ) {
/* Enable 'Normal' Mode */
inst->SMBCTL3 &= ~(BIT(NPCX_SMBCTL3_400K));
/* Set freq of SCL */
/* Set freq of SCL. For 100KHz, only k1 is used. */
SET_FIELD(inst->SMBCTL2, NPCX_SMBCTL2_SCLFRQ0_6_FIELD,
bus_cfg.k1/2 & 0x7f);
SET_FIELD(inst->SMBCTL3, NPCX_SMBCTL3_SCLFRQ7_8_FIELD,
bus_cfg.k2/2 >> 7);
bus_cfg.k1/2 >> 7);
SET_FIELD(inst->SMBCTL4, NPCX_SMBCTL4_HLDT_FIELD,
bus_cfg.HLDT);
} else {
/* Enable 'Fast' Mode for 400K or higher freq. */
inst->SMBCTL3 |= BIT(NPCX_SMBCTL3_400K);