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Date: Wed, 4 May 2016 22:34:32 +0800
From: David Wu <david.wu@...k-chips.com>
To: heiko@...ech.de, wsa@...-dreams.de
Cc: robh+dt@...nel.org, dianders@...omium.org,
andy.shevchenko@...il.com, pawel.moll@....com,
mark.rutland@....com, ijc+devicetree@...lion.org.uk,
galak@...eaurora.org, briannorris@...gle.com,
davidriley@...gle.com, huangtao@...k-chips.com, hl@...k-chips.com,
xjq@...k-chips.com, zyw@...k-chips.com, cf@...k-chips.com,
linux-arm-kernel@...ts.infradead.org,
linux-rockchip@...ts.infradead.org, linux-i2c@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
David Wu <david.wu@...k-chips.com>
Subject: [PATCH v7 6/9] i2c: rk3x: Move spec timing data to "static const" structs
Signed-off-by: David Wu <david.wu@...k-chips.com>
---
drivers/i2c/busses/i2c-rk3x.c | 100 ++++++++++++++++++++++++++++++------------
1 file changed, 72 insertions(+), 28 deletions(-)
diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index 9686c81..408f9ab 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -76,6 +76,51 @@ enum {
#define DEFAULT_SCL_RATE (100 * 1000) /* Hz */
/**
+ * struct i2c_spec_values:
+ * @min_hold_start_ns: min hold time (repeated) START condition
+ * @min_low_ns: min LOW period of the SCL clock
+ * @min_high_ns: min HIGH period of the SCL cloc
+ * @min_setup_start_ns: min set-up time for a repeated START conditio
+ * @max_data_hold_ns: max data hold time
+ * @min_data_setup_ns: min data set-up time
+ * @min_setup_stop_ns: min set-up time for STOP condition
+ * @min_hold_buffer_ns: min bus free time between a STOP and
+ * START condition
+ */
+struct i2c_spec_values {
+ unsigned long min_hold_start_ns;
+ unsigned long min_low_ns;
+ unsigned long min_high_ns;
+ unsigned long min_setup_start_ns;
+ unsigned long max_data_hold_ns;
+ unsigned long min_data_setup_ns;
+ unsigned long min_setup_stop_ns;
+ unsigned long min_hold_buffer_ns;
+};
+
+static const struct i2c_spec_values standard_mode_spec = {
+ .min_hold_start_ns = 4000,
+ .min_low_ns = 4700,
+ .min_high_ns = 4000,
+ .min_setup_start_ns = 4700,
+ .max_data_hold_ns = 3450,
+ .min_data_setup_ns = 250,
+ .min_setup_stop_ns = 4000,
+ .min_hold_buffer_ns = 4700,
+};
+
+static const struct i2c_spec_values fast_mode_spec = {
+ .min_hold_start_ns = 600,
+ .min_low_ns = 1300,
+ .min_high_ns = 600,
+ .min_setup_start_ns = 600,
+ .max_data_hold_ns = 900,
+ .min_data_setup_ns = 100,
+ .min_setup_stop_ns = 600,
+ .min_hold_buffer_ns = 1300,
+};
+
+/**
* struct rk3x_i2c_calced_timings:
* @div_low: Divider output for low
* @div_high: Divider output for high
@@ -463,6 +508,21 @@ out:
}
/**
+ * Get timing values of I2C specification
+ *
+ * @speed: Desired SCL frequency
+ *
+ * Returns: Matched i2c spec values.
+ */
+static const struct i2c_spec_values *rk3x_i2c_get_spec(unsigned int speed)
+{
+ if (speed <= 100000)
+ return &standard_mode_spec;
+ else
+ return &fast_mode_spec;
+}
+
+/**
* Calculate divider values for desired SCL frequency
*
* @clk_rate: I2C input clock rate
@@ -477,10 +537,6 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate,
struct i2c_timings *t,
struct rk3x_i2c_calced_timings *t_calc)
{
- unsigned long spec_min_low_ns, spec_min_high_ns;
- unsigned long spec_setup_start, spec_max_data_hold_ns;
- unsigned long data_hold_buffer_ns;
-
unsigned long min_low_ns, min_high_ns;
unsigned long max_low_ns, min_total_ns;
@@ -492,6 +548,8 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate,
unsigned long min_div_for_hold, min_total_div;
unsigned long extra_div, extra_low_div, ideal_low_div;
+ unsigned long data_hold_buffer_ns = 50;
+ const struct i2c_spec_values *spec;
int ret = 0;
/* Only support standard-mode and fast-mode */
@@ -514,22 +572,8 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate,
* This is because the i2c host on Rockchip holds the data line
* for half the low time.
*/
- if (t->bus_freq_hz <= 100000) {
- /* Standard-mode */
- spec_min_low_ns = 4700;
- spec_setup_start = 4700;
- spec_min_high_ns = 4000;
- spec_max_data_hold_ns = 3450;
- data_hold_buffer_ns = 50;
- } else {
- /* Fast-mode */
- spec_min_low_ns = 1300;
- spec_setup_start = 600;
- spec_min_high_ns = 600;
- spec_max_data_hold_ns = 900;
- data_hold_buffer_ns = 50;
- }
- min_high_ns = t->scl_rise_ns + spec_min_high_ns;
+ spec = rk3x_i2c_get_spec(t->bus_freq_hz);
+ min_high_ns = t->scl_rise_ns + spec->min_high_ns;
/*
* Timings for repeated start:
@@ -539,14 +583,14 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate,
* We need to account for those rules in picking our "high" time so
* we meet tSU;STA and tHD;STA times.
*/
- min_high_ns = max(min_high_ns,
- DIV_ROUND_UP((t->scl_rise_ns + spec_setup_start) * 1000, 875));
- min_high_ns = max(min_high_ns,
- DIV_ROUND_UP((t->scl_rise_ns + spec_setup_start +
- t->sda_fall_ns + spec_min_high_ns), 2));
-
- min_low_ns = t->scl_fall_ns + spec_min_low_ns;
- max_low_ns = spec_max_data_hold_ns * 2 - data_hold_buffer_ns;
+ min_high_ns = max(min_high_ns, DIV_ROUND_UP(
+ (t->scl_rise_ns + spec->min_setup_start_ns) * 1000, 875));
+ min_high_ns = max(min_high_ns, DIV_ROUND_UP(
+ (t->scl_rise_ns + spec->min_setup_start_ns + t->sda_fall_ns +
+ spec->min_high_ns), 2));
+
+ min_low_ns = t->scl_fall_ns + spec->min_low_ns;
+ max_low_ns = spec->max_data_hold_ns * 2 - data_hold_buffer_ns;
min_total_ns = min_low_ns + min_high_ns;
/* Adjust to avoid overflow */
--
1.9.1
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