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i2c: designware: Support non-standard bus speeds

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Add support for non-standard bus speeds by treating them as detuned
versions of the slowest standard speed not less than the requested
speed.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
This commit is contained in:
Phil Elwell
2024-01-16 16:03:14 +00:00
committed by Dom Cobley
parent 8e2ce41985
commit 17a0c20e4f
3 changed files with 51 additions and 12 deletions
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27
drivers/i2c/busses/i2c-designware-common.c
View File

@@ -362,6 +362,9 @@ static void i2c_dw_adjust_bus_speed(struct dw_i2c_dev *dev)
{
u32 acpi_speed = i2c_dw_acpi_round_bus_speed(dev->dev);
struct i2c_timings *t = &dev->timings;
u32 wanted_speed;
u32 legal_speed = 0;
int i;
/*
* Find bus speed from the "clock-frequency" device property, ACPI
@@ -373,6 +376,30 @@ static void i2c_dw_adjust_bus_speed(struct dw_i2c_dev *dev)
t->bus_freq_hz = max(t->bus_freq_hz, acpi_speed);
else
t->bus_freq_hz = I2C_MAX_FAST_MODE_FREQ;
wanted_speed = t->bus_freq_hz;
/* For unsupported speeds, scale down the lowest speed which is faster. */
for (i = 0; i < ARRAY_SIZE(supported_speeds); i++) {
/* supported speeds is in decreasing order */
if (wanted_speed == supported_speeds[i]) {
legal_speed = 0;
break;
}
if (wanted_speed > supported_speeds[i])
break;
legal_speed = supported_speeds[i];
}
if (legal_speed) {
/*
* Pretend this was the requested speed, but preserve the preferred
* speed so the clock counts can be scaled.
*/
t->bus_freq_hz = legal_speed;
dev->wanted_bus_speed = wanted_speed;
}
}
int i2c_dw_fw_parse_and_configure(struct dw_i2c_dev *dev)

1
drivers/i2c/busses/i2c-designware-core.h
View File

@@ -297,6 +297,7 @@ struct dw_i2c_dev {
u16 fp_lcnt;
u16 hs_hcnt;
u16 hs_lcnt;
u32 wanted_bus_speed;
int (*acquire_lock)(void);
void (*release_lock)(void);
int semaphore_idx;

35
drivers/i2c/busses/i2c-designware-master.c
View File

@@ -41,20 +41,32 @@ static void i2c_dw_configure_fifo_master(struct dw_i2c_dev *dev)
regmap_write(dev->map, DW_IC_CON, dev->master_cfg);
}
static u16 clock_calc(struct dw_i2c_dev *dev, bool want_high)
static u32 linear_interpolate(u32 x, u32 x1, u32 x2, u32 y1, u32 y2)
{
return ((x - x1) * y2 + (x2 - x) * y1) / (x2 - x1);
}
static u16 u16_clamp(u32 v)
{
return (u16)min(v, 0xffff);
}
static void clock_calc(struct dw_i2c_dev *dev, u32 *hcnt, u32 *lcnt)
{
struct i2c_timings *t = &dev->timings;
u32 wanted_speed = t->bus_freq_hz;
u32 wanted_khz = (dev->wanted_bus_speed ?: t->bus_freq_hz)/1000;
u32 clk_khz = i2c_dw_clk_rate(dev);
u32 extra_ns = want_high ? t->scl_fall_ns : t->scl_rise_ns;
u32 extra_cycles = (u32)((u64)clk_khz * extra_ns / 1000000);
u32 period = ((u64)clk_khz * 1000 + wanted_speed - 1) / wanted_speed;
u32 cycles = (period + want_high)/2 - extra_cycles;
u32 min_high_ns = (wanted_khz <= 100) ? 4000 :
(wanted_khz <= 400) ?
linear_interpolate(wanted_khz, 100, 400, 4000, 600) :
linear_interpolate(wanted_khz, 400, 1000, 600, 260);
u32 high_cycles = (u32)(((u64)clk_khz * min_high_ns + 999999) / 1000000) + 1;
u32 extra_high_cycles = (u32)((u64)clk_khz * t->scl_fall_ns / 1000000);
u32 extra_low_cycles = (u32)((u64)clk_khz * t->scl_rise_ns / 1000000);
u32 period = ((u64)clk_khz + wanted_khz - 1) / wanted_khz;
if (cycles > 0xffff)
cycles = 0xffff;
return (u16)cycles;
*hcnt = u16_clamp(high_cycles - extra_high_cycles);
*lcnt = u16_clamp(period - high_cycles - extra_low_cycles);
}
static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
@@ -80,8 +92,7 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
sda_falling_time = t->sda_fall_ns ?: 300; /* ns */
scl_falling_time = t->scl_fall_ns ?: 300; /* ns */
hcnt = clock_calc(dev, true);
lcnt = clock_calc(dev, false);
clock_calc(dev, &hcnt, &lcnt);
/* Calculate SCL timing parameters for standard mode if not set */
if (!dev->ss_hcnt || !dev->ss_lcnt) {