[PATCH] i2c: mediatek: Add i2c ac-timing adjust support

From: qii.wang
Date: Thu Mar 26 2020 - 07:54:45 EST

From: Qii Wang <qii.wang@xxxxxxxxxxxx>

This patch adds a algorithm to calculate some ac-timing parameters
which can fully meet I2C Spec.

Signed-off-by: Qii Wang <qii.wang@xxxxxxxxxxxx>
---
drivers/i2c/busses/i2c-mt65xx.c | 332 ++++++++++++++++++++++++++++++++++------
1 file changed, 281 insertions(+), 51 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index 2152ec5f..4da9aac 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -40,12 +40,11 @@
#define I2C_SOFT_RST 0x0001
#define I2C_FIFO_ADDR_CLR 0x0001
#define I2C_DELAY_LEN 0x0002
-#define I2C_ST_START_CON 0x8001
-#define I2C_FS_START_CON 0x1800
#define I2C_TIME_CLR_VALUE 0x0000
#define I2C_TIME_DEFAULT_VALUE 0x0003
#define I2C_WRRD_TRANAC_VALUE 0x0002
#define I2C_RD_TRANAC_VALUE 0x0001
+#define I2C_SCL_MIS_COMP_VALUE 0x0000

#define I2C_DMA_CON_TX 0x0000
#define I2C_DMA_CON_RX 0x0001
@@ -55,13 +54,16 @@
#define I2C_DMA_HARD_RST 0x0002
#define I2C_DMA_4G_MODE 0x0001

-#define I2C_DEFAULT_CLK_DIV 5
#define I2C_DEFAULT_SPEED 100000 /* hz */
#define MAX_FS_MODE_SPEED 400000
#define MAX_HS_MODE_SPEED 3400000
#define MAX_SAMPLE_CNT_DIV 8
#define MAX_STEP_CNT_DIV 64
+#define MAX_CLOCK_DIV 256
#define MAX_HS_STEP_CNT_DIV 8
+#define I2C_STANDARD_MODE_BUFFER (1000 / 2)
+#define I2C_FAST_MODE_BUFFER (300 / 2)
+#define I2C_FAST_MODE_PLUS_BUFFER (20 / 2)

#define I2C_CONTROL_RS (0x1 << 1)
#define I2C_CONTROL_DMA_EN (0x1 << 2)
@@ -126,6 +128,12 @@ enum I2C_REGS_OFFSET {
OFFSET_TRANSFER_LEN_AUX,
OFFSET_CLOCK_DIV,
OFFSET_LTIMING,
+ OFFSET_SCL_HIGH_LOW_RATIO,
+ OFFSET_HS_SCL_HIGH_LOW_RATIO,
+ OFFSET_SCL_MIS_COMP_POINT,
+ OFFSET_STA_STO_AC_TIMING,
+ OFFSET_HS_STA_STO_AC_TIMING,
+ OFFSET_SDA_TIMING,
};

static const u16 mt_i2c_regs_v1[] = {
@@ -153,6 +161,12 @@ enum I2C_REGS_OFFSET {
[OFFSET_DEBUGCTRL] = 0x68,
[OFFSET_TRANSFER_LEN_AUX] = 0x6c,
[OFFSET_CLOCK_DIV] = 0x70,
+ [OFFSET_SCL_HIGH_LOW_RATIO] = 0x74,
+ [OFFSET_HS_SCL_HIGH_LOW_RATIO] = 0x78,
+ [OFFSET_SCL_MIS_COMP_POINT] = 0x7C,
+ [OFFSET_STA_STO_AC_TIMING] = 0x80,
+ [OFFSET_HS_STA_STO_AC_TIMING] = 0x84,
+ [OFFSET_SDA_TIMING] = 0x88,
};

static const u16 mt_i2c_regs_v2[] = {
@@ -171,9 +185,11 @@ enum I2C_REGS_OFFSET {
[OFFSET_HS] = 0x30,
[OFFSET_IO_CONFIG] = 0x34,
[OFFSET_FIFO_ADDR_CLR] = 0x38,
+ [OFFSET_SDA_TIMING] = 0x3c,
[OFFSET_TRANSFER_LEN_AUX] = 0x44,
[OFFSET_CLOCK_DIV] = 0x48,
[OFFSET_SOFTRESET] = 0x50,
+ [OFFSET_SCL_MIS_COMP_POINT] = 0x90,
[OFFSET_DEBUGSTAT] = 0xe0,
[OFFSET_DEBUGCTRL] = 0xe8,
[OFFSET_FIFO_STAT] = 0xf4,
@@ -194,6 +210,19 @@ struct mtk_i2c_compatible {
unsigned char ltiming_adjust: 1;
};

+struct mtk_i2c_ac_timing {
+ u16 htiming;
+ u16 ltiming;
+ u16 hs;
+ u16 ext;
+ u16 inter_clk_div;
+ u16 scl_hl_ratio;
+ u16 hs_scl_hl_ratio;
+ u16 sta_stop;
+ u16 hs_sta_stop;
+ u16 sda_timing;
+};
+
struct mtk_i2c {
struct i2c_adapter adap; /* i2c host adapter */
struct device *dev;
@@ -218,9 +247,46 @@ struct mtk_i2c {
u16 ltiming_reg;
unsigned char auto_restart;
bool ignore_restart_irq;
+ struct mtk_i2c_ac_timing ac_timing;
const struct mtk_i2c_compatible *dev_comp;
};

+/**
+ * struct i2c_spec_values:
+ * min_low_ns: min LOW period of the SCL clock
+ * min_su_sta_ns: min set-up time for a repeated START condition
+ * max_hd_dat_ns: max data hold time
+ * min_su_dat_ns: min data set-up time
+ */
+struct i2c_spec_values {
+ unsigned int min_low_ns;
+ unsigned int min_high_ns;
+ unsigned int min_su_sta_ns;
+ unsigned int max_hd_dat_ns;
+ unsigned int min_su_dat_ns;
+};
+
+static const struct i2c_spec_values standard_mode_spec = {
+ .min_low_ns = 4700 + I2C_STANDARD_MODE_BUFFER,
+ .min_su_sta_ns = 4700 + I2C_STANDARD_MODE_BUFFER,
+ .max_hd_dat_ns = 3450 - I2C_STANDARD_MODE_BUFFER,
+ .min_su_dat_ns = 250 + I2C_STANDARD_MODE_BUFFER,
+};
+
+static const struct i2c_spec_values fast_mode_spec = {
+ .min_low_ns = 1300 + I2C_FAST_MODE_BUFFER,
+ .min_su_sta_ns = 600 + I2C_FAST_MODE_BUFFER,
+ .max_hd_dat_ns = 900 - I2C_FAST_MODE_BUFFER,
+ .min_su_dat_ns = 100 + I2C_FAST_MODE_BUFFER,
+};
+
+static const struct i2c_spec_values fast_mode_plus_spec = {
+ .min_low_ns = 500 + I2C_FAST_MODE_PLUS_BUFFER,
+ .min_su_sta_ns = 260 + I2C_FAST_MODE_PLUS_BUFFER,
+ .max_hd_dat_ns = 400 - I2C_FAST_MODE_PLUS_BUFFER,
+ .min_su_dat_ns = 50 + I2C_FAST_MODE_PLUS_BUFFER,
+};
+
static const struct i2c_adapter_quirks mt6577_i2c_quirks = {
.flags = I2C_AQ_COMB_WRITE_THEN_READ,
.max_num_msgs = 1,
@@ -400,14 +466,38 @@ static void mtk_i2c_init_hw(struct mtk_i2c *i2c)
if (i2c->dev_comp->dcm)
mtk_i2c_writew(i2c, I2C_DCM_DISABLE, OFFSET_DCM_EN);

- if (i2c->dev_comp->timing_adjust)
- mtk_i2c_writew(i2c, I2C_DEFAULT_CLK_DIV - 1, OFFSET_CLOCK_DIV);
-
mtk_i2c_writew(i2c, i2c->timing_reg, OFFSET_TIMING);
mtk_i2c_writew(i2c, i2c->high_speed_reg, OFFSET_HS);
if (i2c->dev_comp->ltiming_adjust)
mtk_i2c_writew(i2c, i2c->ltiming_reg, OFFSET_LTIMING);

+ if (i2c->dev_comp->timing_adjust) {
+ mtk_i2c_writew(i2c, i2c->ac_timing.ext, OFFSET_EXT_CONF);
+ mtk_i2c_writew(i2c, i2c->ac_timing.inter_clk_div,
+ OFFSET_CLOCK_DIV);
+ mtk_i2c_writew(i2c, I2C_SCL_MIS_COMP_VALUE,
+ OFFSET_SCL_MIS_COMP_POINT);
+ mtk_i2c_writew(i2c, i2c->ac_timing.sda_timing,
+ OFFSET_SDA_TIMING);
+
+ if (i2c->dev_comp->ltiming_adjust) {
+ mtk_i2c_writew(i2c, i2c->ac_timing.htiming,
+ OFFSET_TIMING);
+ mtk_i2c_writew(i2c, i2c->ac_timing.hs, OFFSET_HS);
+ mtk_i2c_writew(i2c, i2c->ac_timing.ltiming,
+ OFFSET_LTIMING);
+ } else {
+ mtk_i2c_writew(i2c, i2c->ac_timing.scl_hl_ratio,
+ OFFSET_SCL_HIGH_LOW_RATIO);
+ mtk_i2c_writew(i2c, i2c->ac_timing.hs_scl_hl_ratio,
+ OFFSET_HS_SCL_HIGH_LOW_RATIO);
+ mtk_i2c_writew(i2c, i2c->ac_timing.sta_stop,
+ OFFSET_STA_STO_AC_TIMING);
+ mtk_i2c_writew(i2c, i2c->ac_timing.hs_sta_stop,
+ OFFSET_HS_STA_STO_AC_TIMING);
+ }
+ }
+
/* If use i2c pin from PMIC mt6397 side, need set PATH_DIR first */
if (i2c->have_pmic)
mtk_i2c_writew(i2c, I2C_CONTROL_WRAPPER, OFFSET_PATH_DIR);
@@ -425,6 +515,129 @@ static void mtk_i2c_init_hw(struct mtk_i2c *i2c)
writel(I2C_DMA_CLR_FLAG, i2c->pdmabase + OFFSET_RST);
}

+static const struct i2c_spec_values *mtk_i2c_get_spec(unsigned int speed)
+{
+ if (speed <= I2C_DEFAULT_SPEED)
+ return &standard_mode_spec;
+ else if (speed <= MAX_FS_MODE_SPEED)
+ return &fast_mode_spec;
+ else
+ return &fast_mode_plus_spec;
+}
+
+static int mtk_i2c_max_step_cnt(unsigned int target_speed)
+{
+ if (target_speed > MAX_FS_MODE_SPEED)
+ return MAX_HS_STEP_CNT_DIV;
+ else
+ return MAX_STEP_CNT_DIV;
+}
+
+/*
+ * Check and Calculate i2c ac-timing
+ *
+ * Hardware design:
+ * sample_ns = (1000000000 * (sample_cnt + 1)) / clk_src
+ * xxx_cnt_div = spec->min_xxx_ns / sample_ns
+ *
+ * Sample_ns is rounded down for xxx_cnt_div would be greater
+ * than the smallest spec.
+ * The sda_timing is chosen as the middle value between
+ * the largest and smallest.
+ */
+static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
+ unsigned int clk_src,
+ unsigned int check_speed,
+ unsigned int step_cnt,
+ unsigned int sample_cnt)
+{
+ const struct i2c_spec_values *spec;
+ unsigned int su_sta_cnt, low_cnt, high_cnt, max_step_cnt;
+ unsigned int sda_max, sda_min, clk_ns, max_sta_cnt = 0x3f;
+ long long sample_ns = (1000000000 * (sample_cnt + 1)) / clk_src;
+
+ if (!i2c->dev_comp->timing_adjust)
+ return 0;
+
+ if (i2c->dev_comp->ltiming_adjust)
+ max_sta_cnt = 0x100;
+
+ spec = mtk_i2c_get_spec(check_speed);
+
+ if (i2c->dev_comp->ltiming_adjust)
+ clk_ns = 1000000000 / clk_src;
+ else
+ clk_ns = sample_ns / 2;
+
+ su_sta_cnt = DIV_ROUND_UP(spec->min_su_sta_ns, clk_ns);
+ if (su_sta_cnt > max_sta_cnt)
+ return -1;
+
+ low_cnt = DIV_ROUND_UP(spec->min_low_ns, sample_ns);
+ max_step_cnt = mtk_i2c_max_step_cnt(check_speed);
+ if ((2 * step_cnt) > low_cnt && low_cnt < max_step_cnt) {
+ if (low_cnt > step_cnt) {
+ high_cnt = 2 * step_cnt - low_cnt;
+ } else {
+ high_cnt = step_cnt;
+ low_cnt = step_cnt;
+ }
+ } else {
+ return -2;
+ }
+
+ sda_max = spec->max_hd_dat_ns / sample_ns;
+ if (sda_max < low_cnt)
+ sda_max = sda_max;
+ else
+ sda_max = 0;
+
+ sda_min = DIV_ROUND_UP(spec->min_su_dat_ns, sample_ns);
+ if (sda_min > low_cnt)
+ sda_min = sda_min;
+ else
+ sda_min = 0;
+
+ if (sda_min > sda_max)
+ return -3;
+
+ if (check_speed > MAX_FS_MODE_SPEED) {
+ if (i2c->dev_comp->ltiming_adjust) {
+ i2c->ac_timing.hs = I2C_TIME_DEFAULT_VALUE |
+ (sample_cnt << 12) | (high_cnt << 8);
+ i2c->ac_timing.ltiming &= ~GENMASK(15, 9);
+ i2c->ac_timing.ltiming |= (sample_cnt << 12) |
+ (low_cnt << 9);
+ i2c->ac_timing.ext &= ~GENMASK(7, 1);
+ i2c->ac_timing.ext |= (su_sta_cnt << 1) | (1 << 0);
+ } else {
+ i2c->ac_timing.hs_scl_hl_ratio = (1 << 12) |
+ (high_cnt << 6) | low_cnt;
+ i2c->ac_timing.hs_sta_stop = (su_sta_cnt << 8) |
+ su_sta_cnt;
+ }
+ i2c->ac_timing.sda_timing &= ~GENMASK(11, 6);
+ i2c->ac_timing.sda_timing |= (1 << 12) |
+ ((sda_max + sda_min) / 2) << 6;
+ } else {
+ if (i2c->dev_comp->ltiming_adjust) {
+ i2c->ac_timing.htiming = (sample_cnt << 8) | (high_cnt);
+ i2c->ac_timing.ltiming = (sample_cnt << 6) | (low_cnt);
+ i2c->ac_timing.ext = (su_sta_cnt << 8) | (1 << 0);
+ } else {
+ i2c->ac_timing.scl_hl_ratio = (1 << 12) |
+ (high_cnt << 6) | low_cnt;
+ i2c->ac_timing.sta_stop = (su_sta_cnt << 8) |
+ su_sta_cnt;
+ }
+
+ i2c->ac_timing.sda_timing = (1 << 12) |
+ (sda_max + sda_min) / 2;
+ }
+
+ return 0;
+}
+
/*
* Calculate i2c port speed
*
@@ -449,15 +662,12 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
unsigned int opt_div;
unsigned int best_mul;
unsigned int cnt_mul;
+ int ret = -EINVAL;

if (target_speed > MAX_HS_MODE_SPEED)
target_speed = MAX_HS_MODE_SPEED;

- if (target_speed > MAX_FS_MODE_SPEED)
- max_step_cnt = MAX_HS_STEP_CNT_DIV;
- else
- max_step_cnt = MAX_STEP_CNT_DIV;
-
+ max_step_cnt = mtk_i2c_max_step_cnt(target_speed);
base_step_cnt = max_step_cnt;
/* Find the best combination */
opt_div = DIV_ROUND_UP(clk_src >> 1, target_speed);
@@ -476,6 +686,11 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
continue;

if (cnt_mul < best_mul) {
+ ret = mtk_i2c_check_ac_timing(i2c, clk_src,
+ target_speed, step_cnt - 1, sample_cnt - 1);
+ if (ret)
+ continue;
+
best_mul = cnt_mul;
base_sample_cnt = sample_cnt;
base_step_cnt = step_cnt;
@@ -484,6 +699,9 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
}
}

+ if (ret)
+ return -EINVAL;
+
sample_cnt = base_sample_cnt;
step_cnt = base_step_cnt;

@@ -509,47 +727,68 @@ static int mtk_i2c_set_speed(struct mtk_i2c *i2c, unsigned int parent_clk)
unsigned int l_step_cnt;
unsigned int l_sample_cnt;
unsigned int target_speed;
+ unsigned int clk_div;
+ unsigned int max_clk_div;
int ret;

- clk_src = parent_clk / i2c->clk_src_div;
target_speed = i2c->speed_hz;
+ parent_clk /= i2c->clk_src_div;

- if (target_speed > MAX_FS_MODE_SPEED) {
- /* Set master code speed register */
- ret = mtk_i2c_calculate_speed(i2c, clk_src, MAX_FS_MODE_SPEED,
- &l_step_cnt, &l_sample_cnt);
- if (ret < 0)
- return ret;
-
- i2c->timing_reg = (l_sample_cnt << 8) | l_step_cnt;
-
- /* Set the high speed mode register */
- ret = mtk_i2c_calculate_speed(i2c, clk_src, target_speed,
- &step_cnt, &sample_cnt);
- if (ret < 0)
- return ret;
-
- i2c->high_speed_reg = I2C_TIME_DEFAULT_VALUE |
- (sample_cnt << 12) | (step_cnt << 8);
+ if (i2c->dev_comp->timing_adjust)
+ max_clk_div = MAX_CLOCK_DIV;
+ else
+ max_clk_div = 1;
+
+ for (clk_div = 1; clk_div <= max_clk_div; clk_div++) {
+ clk_src = parent_clk / clk_div;
+
+ if (target_speed > MAX_FS_MODE_SPEED) {
+ /* Set master code speed register */
+ ret = mtk_i2c_calculate_speed(i2c, clk_src,
+ MAX_FS_MODE_SPEED,
+ &l_step_cnt,
+ &l_sample_cnt);
+ if (ret < 0)
+ continue;
+
+ i2c->timing_reg = (l_sample_cnt << 8) | l_step_cnt;
+
+ /* Set the high speed mode register */
+ ret = mtk_i2c_calculate_speed(i2c, clk_src,
+ target_speed, &step_cnt,
+ &sample_cnt);
+ if (ret < 0)
+ continue;
+
+ i2c->high_speed_reg = I2C_TIME_DEFAULT_VALUE |
+ (sample_cnt << 12) | (step_cnt << 8);
+
+ if (i2c->dev_comp->ltiming_adjust)
+ i2c->ltiming_reg =
+ (l_sample_cnt << 6) | l_step_cnt |
+ (sample_cnt << 12) | (step_cnt << 9);
+ } else {
+ ret = mtk_i2c_calculate_speed(i2c, clk_src,
+ target_speed, &l_step_cnt,
+ &l_sample_cnt);
+ if (ret < 0)
+ continue;

- if (i2c->dev_comp->ltiming_adjust)
- i2c->ltiming_reg = (l_sample_cnt << 6) | l_step_cnt |
- (sample_cnt << 12) | (step_cnt << 9);
- } else {
- ret = mtk_i2c_calculate_speed(i2c, clk_src, target_speed,
- &step_cnt, &sample_cnt);
- if (ret < 0)
- return ret;
+ i2c->timing_reg = (l_sample_cnt << 8) | l_step_cnt;

- i2c->timing_reg = (sample_cnt << 8) | step_cnt;
+ /* Disable the high speed transaction */
+ i2c->high_speed_reg = I2C_TIME_CLR_VALUE;

- /* Disable the high speed transaction */
- i2c->high_speed_reg = I2C_TIME_CLR_VALUE;
+ if (i2c->dev_comp->ltiming_adjust)
+ i2c->ltiming_reg =
+ (l_sample_cnt << 6) | l_step_cnt;
+ }

- if (i2c->dev_comp->ltiming_adjust)
- i2c->ltiming_reg = (sample_cnt << 6) | step_cnt;
+ break;
}

+ i2c->ac_timing.inter_clk_div = clk_div - 1;
+
return 0;
}

@@ -589,12 +828,6 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,

mtk_i2c_writew(i2c, control_reg, OFFSET_CONTROL);

- /* set start condition */
- if (i2c->speed_hz <= I2C_DEFAULT_SPEED)
- mtk_i2c_writew(i2c, I2C_ST_START_CON, OFFSET_EXT_CONF);
- else
- mtk_i2c_writew(i2c, I2C_FS_START_CON, OFFSET_EXT_CONF);
-
addr_reg = i2c_8bit_addr_from_msg(msgs);
mtk_i2c_writew(i2c, addr_reg, OFFSET_SLAVE_ADDR);

@@ -951,9 +1184,6 @@ static int mtk_i2c_probe(struct platform_device *pdev)
if (ret)
return -EINVAL;

- if (i2c->dev_comp->timing_adjust)
- i2c->clk_src_div *= I2C_DEFAULT_CLK_DIV;
-
if (i2c->have_pmic && !i2c->dev_comp->pmic_i2c)
return -EINVAL;

--
1.9.1