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Date: Wed, 11 May 2016 03:29:58 +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 v8 5/8] i2c: rk3x: Move spec timing data to "static const" structs
The i2c timing specs are really just constant data. There's no reason
to write code to init them, so move them out to structures. This not
only is a cleaner solution but it will reduce code duplication when we
introduce a new variant of rk3x_i2c_calc_divs() in a future patch.
Signed-off-by: David Wu <david.wu@...k-chips.com>
Suggested-by: Douglas Anderson <dianders@...omium.org>
Reviewed-by: Douglas Anderson <dianders@...omium.org>
---
Changes in v8:
- add commit description.
- remove the spec values that were not needed, then
introduce the additional values in the rk3399 patch.
drivers/i2c/busses/i2c-rk3x.c | 83 ++++++++++++++++++++++++++++---------------
1 file changed, 55 insertions(+), 28 deletions(-)
diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index d7a871f..9791797 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -76,6 +76,34 @@ enum {
#define DEFAULT_SCL_RATE (100 * 1000) /* Hz */
/**
+ * struct i2c_spec_values:
+ * @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
+ */
+struct i2c_spec_values {
+ unsigned long min_low_ns;
+ unsigned long min_high_ns;
+ unsigned long min_setup_start_ns;
+ unsigned long max_data_hold_ns;
+};
+
+static const struct i2c_spec_values standard_mode_spec = {
+ .min_low_ns = 4700,
+ .min_high_ns = 4000,
+ .min_setup_start_ns = 4700,
+ .max_data_hold_ns = 3450,
+};
+
+static const struct i2c_spec_values fast_mode_spec = {
+ .min_low_ns = 1300,
+ .min_high_ns = 600,
+ .min_setup_start_ns = 600,
+ .max_data_hold_ns = 900,
+};
+
+/**
* struct rk3x_i2c_calced_timings:
* @div_low: Divider output for low
* @div_high: Divider output for high
@@ -460,6 +488,21 @@ 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
@@ -474,10 +517,6 @@ 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;
@@ -489,6 +528,8 @@ 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 */
@@ -511,22 +552,8 @@ 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:
@@ -536,14 +563,14 @@ 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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