From: David Wu <david.wu@rock-chips.com>
To: heiko@sntech.de, wsa@the-dreams.de
Cc: robh+dt@kernel.org, dianders@chromium.org,
andy.shevchenko@gmail.com, pawel.moll@arm.com,
mark.rutland@arm.com, ijc+devicetree@hellion.org.uk,
galak@codeaurora.org, briannorris@google.com,
davidriley@google.com, huangtao@rock-chips.com,
hl@rock-chips.com, xjq@rock-chips.com, zyw@rock-chips.com,
cf@rock-chips.com, linux-arm-kernel@lists.infradead.org,
linux-rockchip@lists.infradead.org, linux-i2c@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
David Wu <david.wu@rock-chips.com>
Subject: [PATCH v10 5/8] i2c: rk3x: Move spec timing data to "static const" structs
Date: Mon, 16 May 2016 22:03:24 +0800 [thread overview]
Message-ID: <1463407404-41370-1-git-send-email-david.wu@rock-chips.com> (raw)
In-Reply-To: <1463407063-41218-1-git-send-email-david.wu@rock-chips.com>
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@rock-chips.com>
Suggested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
---
Change in v10:
- none
Change in v9:
- none
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
next prev parent reply other threads:[~2016-05-16 14:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-16 13:57 [PATCH v10 0/8] add i2c driver supported for rk3399 David Wu
2016-05-16 13:57 ` [PATCH v10 1/8] i2c: rk3x: add documentation to fields in "struct rk3x_i2c" David Wu
2016-05-16 13:57 ` [PATCH v10 2/8] i2c: rk3x: use struct "rk3x_i2c_calced_timings" David Wu
2016-05-16 13:57 ` [PATCH v10 3/8] i2c: rk3x: Remove redundant rk3x_i2c_clean_ipd() David Wu
2016-05-16 13:57 ` [PATCH v10 4/8] i2c: rk3x: Change SoC data to not use array David Wu
2016-05-16 14:03 ` David Wu [this message]
2016-05-16 14:04 ` [PATCH v10 6/8] dt-bindings: i2c: rk3x: add support for rk3399 David Wu
2016-05-16 16:45 ` Rob Herring
2016-05-16 14:05 ` [PATCH v10 7/8] i2c: rk3x: add i2c support for rk3399 soc David Wu
2016-05-16 17:22 ` Doug Anderson
2016-05-16 14:06 ` [PATCH v10 8/8] i2c: rk3x: support fast-mode plus for rk3399 David Wu
2016-05-16 20:17 ` [PATCH v10 0/8] add i2c driver supported " Doug Anderson
2016-06-08 15:47 ` Heiko Stübner
2016-06-09 7:47 ` Wolfram Sang
2016-06-09 14:12 ` Heiko Stübner
2016-06-17 11:56 ` Wolfram Sang
2016-06-20 2:18 ` David.Wu
2016-06-20 2:18 ` David.Wu
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