[PATCH v9 1/1] i2c: mediatek: modify bus speed calculation formula

Kewei Xu
2022-02-09T09:56:24Z

When clock-div is 0 or greater than 1, the bus speed
calculated by the old speed calculation formula will be
larger than the target speed. So we update the formula.

Signed-off-by: Kewei Xu <kewei.xu@mediatek.com>
Change-Id: Ic0d9b8ab036bcf215d3a5066f2b91c7b8b128ba6
---
drivers/i2c/busses/i2c-mt65xx.c | 51 +++++++++++++++++++++++++++++++++--------
1 file changed, 41 insertions(+), 10 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index aa4d218..682293e 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -67,11 +67,12 @@

#define MAX_SAMPLE_CNT_DIV 8
#define MAX_STEP_CNT_DIV 64
-#define MAX_CLOCK_DIV 256
+#define MAX_CLOCK_DIV_8BITS 256
+#define MAX_CLOCK_DIV_5BITS 32
#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_STANDARD_MODE_BUFFER (1000 / 3)
+#define I2C_FAST_MODE_BUFFER (300 / 3)
+#define I2C_FAST_MODE_PLUS_BUFFER (20 / 3)

#define I2C_CONTROL_RS (0x1 << 1)
#define I2C_CONTROL_DMA_EN (0x1 << 2)
@@ -604,6 +605,31 @@ static int mtk_i2c_max_step_cnt(unsigned int target_speed)
return MAX_STEP_CNT_DIV;
}

+static int mtk_i2c_get_clk_div_restri(struct mtk_i2c *i2c,
+ unsigned int sample_cnt)
+{
+ int clk_div_restri = 0;
+
+ if (i2c->dev_comp->ltiming_adjust == 0)
+ return 0;
+
+ if (sample_cnt == 1) {
+ if (i2c->ac_timing.inter_clk_div == 0)
+ clk_div_restri = 0;
+ else
+ clk_div_restri = 1;
+ } else {
+ if (i2c->ac_timing.inter_clk_div == 0)
+ clk_div_restri = -1;
+ else if (i2c->ac_timing.inter_clk_div == 1)
+ clk_div_restri = 0;
+ else
+ clk_div_restri = 1;
+ }
+
+ return clk_div_restri;
+}
+
/*
* Check and Calculate i2c ac-timing
*
@@ -732,6 +758,7 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
unsigned int best_mul;
unsigned int cnt_mul;
int ret = -EINVAL;
+ int clk_div_restri = 0;

if (target_speed > I2C_MAX_HIGH_SPEED_MODE_FREQ)
target_speed = I2C_MAX_HIGH_SPEED_MODE_FREQ;
@@ -749,7 +776,8 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
* optimizing for sample_cnt * step_cnt being minimal
*/
for (sample_cnt = 1; sample_cnt <= MAX_SAMPLE_CNT_DIV; sample_cnt++) {
- step_cnt = DIV_ROUND_UP(opt_div, sample_cnt);
+ clk_div_restri = mtk_i2c_get_clk_div_restri(i2c, sample_cnt);
+ step_cnt = DIV_ROUND_UP(opt_div + clk_div_restri, sample_cnt);
cnt_mul = step_cnt * sample_cnt;
if (step_cnt > max_step_cnt)
continue;
@@ -763,7 +791,7 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
best_mul = cnt_mul;
base_sample_cnt = sample_cnt;
base_step_cnt = step_cnt;
- if (best_mul == opt_div)
+ if (best_mul == (opt_div + clk_div_restri))
break;
}
}
@@ -774,7 +802,8 @@ static int mtk_i2c_calculate_speed(struct mtk_i2c *i2c, unsigned int clk_src,
sample_cnt = base_sample_cnt;
step_cnt = base_step_cnt;

- if ((clk_src / (2 * sample_cnt * step_cnt)) > target_speed) {
+ if ((clk_src / (2 * (sample_cnt * step_cnt - clk_div_restri))) >
+ target_speed) {
/* In this case, hardware can't support such
* low i2c_bus_freq
*/
@@ -803,13 +832,16 @@ static int mtk_i2c_set_speed(struct mtk_i2c *i2c, unsigned int parent_clk)
target_speed = i2c->speed_hz;
parent_clk /= i2c->clk_src_div;

- if (i2c->dev_comp->timing_adjust)
- max_clk_div = MAX_CLOCK_DIV;
+ if (i2c->dev_comp->timing_adjust && i2c->dev_comp->ltiming_adjust)
+ max_clk_div = MAX_CLOCK_DIV_5BITS;
+ else if (i2c->dev_comp->timing_adjust)
+ max_clk_div = MAX_CLOCK_DIV_8BITS;
else
max_clk_div = 1;

for (clk_div = 1; clk_div <= max_clk_div; clk_div++) {
clk_src = parent_clk / clk_div;
+ i2c->ac_timing.inter_clk_div = clk_div - 1;

if (target_speed > I2C_MAX_FAST_MODE_PLUS_FREQ) {
/* Set master code speed register */
@@ -856,7 +888,6 @@ static int mtk_i2c_set_speed(struct mtk_i2c *i2c, unsigned int parent_clk)
break;
}

- i2c->ac_timing.inter_clk_div = clk_div - 1;

return 0;
}
--
1.9.1