In commit 35eba185fd1a ("i2c: designware: Calculate SCL timing
parameter for High Speed Mode") hs_hcnt and hs_hcnt are computed based on
fixed tHIGH = 160 and tLOW = 320. However, this fixed values only applies
to the set of conditions of IC_CAP_LOADING = 400pF and
IC_FREQ_OPTIMIZATION = 1. Outside of this conditions set, if this fixed
values are still used, the calculated HCNT and LCNT will make the SCL
frequency unabled to reach 3.4 MHz.
If hs_hcnt and hs_lcnt are calculated based on fixed tHIGH = 160 and
tLOW = 320, SCL frequency may not reach 3.4 MHz when IC_CAP_LOADING is not
400pF or IC_FREQ_OPTIMIZATION is not 1.
Section 3.15.4.5 in DesignWare DW_apb_i2c Databook v2.03 says when
IC_CLK_FREQ_OPTIMIZATION = 0,
MIN_SCL_HIGHtime = 60 ns for 3.4 Mbps, bus loading = 100pF
= 120 ns for 3,4 Mbps, bus loading = 400pF
MIN_SCL_LOWtime = 160 ns for 3.4 Mbps, bus loading = 100pF
= 320 ns for 3.4 Mbps, bus loading = 400pF
and section 3.15.4.6 says when IC_CLK_FREQ_OPTIMIZATION = 1,
MIN_SCL_HIGHtime = 60 ns for 3.4 Mbps, bus loading = 100pF
= 160 ns for 3.4 Mbps, bus loading = 400pF
MIN_SCL_LOWtime = 120 ns for 3.4 Mbps, bus loading = 100pF
= 320 ns for 3.4 Mbps, bus loading = 400pF
In order to calculate more accurate hs_hcnt and hs_lcnt, two hardware
parameters IC_CAP_LOADING and IC_CLK_FREQ_OPTIMIZATION must be
considered together.
Signed-off-by: Michael Wu <michael.wu@xxxxxxxxx>
---
drivers/i2c/busses/i2c-designware-common.c | 16 ++++++++++++++
drivers/i2c/busses/i2c-designware-core.h | 8 +++++++
drivers/i2c/busses/i2c-designware-master.c | 24 +++++++++++++++++++--
drivers/i2c/busses/i2c-designware-platdrv.c | 2 ++
4 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
index e8a688d04aee..f0a7d0ce6fd6 100644
--- a/drivers/i2c/busses/i2c-designware-common.c
+++ b/drivers/i2c/busses/i2c-designware-common.c
@@ -332,6 +332,22 @@ void i2c_dw_adjust_bus_speed(struct dw_i2c_dev *dev)
}
EXPORT_SYMBOL_GPL(i2c_dw_adjust_bus_speed);
+void i2c_dw_parse_of(struct dw_i2c_dev *dev)
+{
+ int ret;
+
+ ret = device_property_read_u32(dev->dev, "bus-loading",
+ &dev->bus_loading);
+ if (ret || dev->bus_loading < 400)
+ dev->bus_loading = 100;
+ else
+ dev->bus_loading = 400;
+
+ dev->clk_freq_optimized =
+ device_property_read_bool(dev->dev, "clk-freq-optimized");
+
+}
+
u32 i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset)
{
/*
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index e9606c00b8d1..064ba3426499 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -242,6 +242,11 @@ struct reset_control;
* @set_sda_hold_time: callback to retrieve IP specific SDA hold timing
* @mode: operation mode - DW_IC_MASTER or DW_IC_SLAVE
* @rinfo: I²C GPIO recovery information
+ * @bus_loading: for high speed mode, the bus loading affects the high and low
+ * pulse width of SCL
+ * @clk_freq_optimized: indicate whether the system clock frequency is reduced
+ * by reducing the internal latency required to generate the high period
+ * and low period of the SCL line
*
* HCNT and LCNT parameters can be used if the platform knows more accurate
* values than the one computed based only on the input clock frequency.
@@ -300,6 +305,8 @@ struct dw_i2c_dev {
int (*set_sda_hold_time)(struct dw_i2c_dev *dev);
int mode;
struct i2c_bus_recovery_info rinfo;
+ u32 bus_loading;
+ bool clk_freq_optimized;
};
#define ACCESS_INTR_MASK BIT(0)
@@ -329,6 +336,7 @@ struct i2c_dw_semaphore_callbacks {
};
int i2c_dw_init_regmap(struct dw_i2c_dev *dev);
+void i2c_dw_parse_of(struct dw_i2c_dev *dev);
u32 i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset);
u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset);
int i2c_dw_set_sda_hold(struct dw_i2c_dev *dev);
diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index c7e56002809a..7b187f68394e 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -140,16 +140,36 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
dev->hs_hcnt = 0;
dev->hs_lcnt = 0;
} else if (!dev->hs_hcnt || !dev->hs_lcnt) {
+ u32 t_high, t_low;
+
+ if (dev->clk_freq_optimized) {
+ if (dev->bus_loading == 400) {
+ t_high = 160;
+ t_low = 320;
+ } else {
+ t_high = 60;
+ t_low = 120;
+ }
+ } else {
+ if (dev->bus_loading == 400) {
+ t_high = 120;
+ t_low = 320;
+ } else {
+ t_high = 60;
+ t_low = 160;
+ }
+ }
+
ic_clk = i2c_dw_clk_rate(dev);
dev->hs_hcnt =
i2c_dw_scl_hcnt(ic_clk,
- 160, /* tHIGH = 160 ns */
+ t_high,
sda_falling_time,
0, /* DW default */
0); /* No offset */
dev->hs_lcnt =
i2c_dw_scl_lcnt(ic_clk,
- 320, /* tLOW = 320 ns */
+ t_low,
scl_falling_time,
0); /* No offset */
}
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index df3dc1e8093e..9fdcf1068a70 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -307,6 +307,8 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
reset_control_deassert(dev->rst);
+ i2c_dw_parse_of(dev);
+
t = &dev->timings;
i2c_parse_fw_timings(&pdev->dev, t, false);
--
2.43.0
