[PATCH v2 05/10] rtc: ac100: Add clk output support

Chen-Yu Tsai
2016-06-15T10:27:42Z

The AC100's RTC side has 3 clock outputs on external pins, which can
provide a clock signal to the SoC or other modules, such as WiFi or
GSM modules.

Support this with a custom clk driver integrated with the rtc driver.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
drivers/rtc/rtc-ac100.c | 319 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 319 insertions(+)

diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
index 360346792ca5..89b63b4bb88f 100644
--- a/drivers/rtc/rtc-ac100.c
+++ b/drivers/rtc/rtc-ac100.c
@@ -15,6 +15,7 @@
*/

#include <linux/bcd.h>
+#include <linux/clk-provider.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
@@ -31,6 +32,15 @@
/* Control register */
#define AC100_RTC_CTRL_24HOUR BIT(0)

+/* Clock output register bits */
+#define AC100_CLK32K_PRE_DIV_SHIFT 5
+#define AC100_CLK32K_PRE_DIV_WIDTH 3
+#define AC100_CLK32K_MUX_SHIFT 4
+#define AC100_CLK32K_MUX_WIDTH 1
+#define AC100_CLK32K_DIV_SHIFT 1
+#define AC100_CLK32K_DIV_WIDTH 3
+#define AC100_CLK32K_EN BIT(0)
+
/* RTC */
#define AC100_RTC_SEC_MASK GENMASK(6, 0)
#define AC100_RTC_MIN_MASK GENMASK(6, 0)
@@ -67,6 +77,26 @@
#define AC100_YEAR_MAX 2069
#define AC100_YEAR_OFF (AC100_YEAR_MIN - 1900)

+struct ac100_clk32k {
+ struct clk_hw hw;
+ struct regmap *regmap;
+ u8 offset;
+};
+
+#define to_ac100_clk32k(_hw) container_of(_hw, struct ac100_clk32k, hw)
+
+#define AC100_RTC_32K_NAME "ac100-rtc-32k"
+#define AC100_RTC_32K_RATE 32768
+#define AC100_ADDA_4M_NAME "ac100-adda-4M"
+#define AC100_ADDA_4M_RATE 4000000
+#define AC100_CLK32K_NUM 3
+
+static const char * const ac100_clk32k_names[] = {
+ "ac100-clk32k-ap",
+ "ac100-clk32k-bb",
+ "ac100-clk32k-md",
+};
+
struct ac100_rtc_dev {
struct rtc_device *rtc;
struct device *dev;
@@ -74,8 +104,283 @@ struct ac100_rtc_dev {
struct mutex mutex;
int irq;
unsigned long alarm;
+
+ struct clk_hw *rtc_32k_clk;
+ struct clk_hw *adda_4M_clk;
+ struct ac100_clk32k clks[AC100_CLK32K_NUM];
+ struct clk_hw_onecell_data *clk_data;
+};
+
+/**
+ * Clock controls for 3 clock output pins
+ */
+
+static const struct clk_div_table ac100_clk32k_prediv[] = {
+ { .val = 0, .div = 1 },
+ { .val = 1, .div = 2 },
+ { .val = 2, .div = 4 },
+ { .val = 3, .div = 8 },
+ { .val = 4, .div = 16 },
+ { .val = 5, .div = 32 },
+ { .val = 6, .div = 64 },
+ { .val = 7, .div = 122 },
+ { },
+};
+
+/* Abuse the fact that one parent is 32768 Hz, and the other is 4 MHz */
+static unsigned long ac100_clk32k_recalc_rate(struct clk_hw *hw,
+ unsigned long prate)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+ unsigned int reg, div;
+
+ regmap_read(clk->regmap, clk->offset, &reg);
+
+ /* Handle pre-divider first */
+ if (prate != AC100_RTC_32K_RATE) {
+ div = (reg >> AC100_CLK32K_PRE_DIV_SHIFT) &
+ ((1 << AC100_CLK32K_PRE_DIV_WIDTH) - 1);
+ prate = divider_recalc_rate(hw, prate, div,
+ ac100_clk32k_prediv, 0);
+ }
+
+ div = (reg >> AC100_CLK32K_DIV_SHIFT) &
+ (BIT(AC100_CLK32K_DIV_WIDTH) - 1);
+ return divider_recalc_rate(hw, prate, div, NULL,
+ CLK_DIVIDER_POWER_OF_TWO);
+}
+
+static long ac100_clk32k_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long prate)
+{
+ unsigned long best_rate = 0, tmp_rate, tmp_prate;
+ int i;
+
+ if (prate == AC100_RTC_32K_RATE)
+ return divider_round_rate(hw, rate, &prate, NULL,
+ AC100_CLK32K_DIV_WIDTH,
+ CLK_DIVIDER_POWER_OF_TWO);
+
+ for (i = 0; ac100_clk32k_prediv[i].div; i++) {
+ tmp_prate = DIV_ROUND_UP(prate, ac100_clk32k_prediv[i].val);
+ tmp_rate = divider_round_rate(hw, rate, &tmp_prate, NULL,
+ AC100_CLK32K_DIV_WIDTH,
+ CLK_DIVIDER_POWER_OF_TWO);
+
+ if (tmp_rate > rate)
+ continue;
+ if (rate - tmp_rate < best_rate - tmp_rate)
+ best_rate = tmp_rate;
+ }
+
+ return best_rate;
+}
+
+static int ac100_clk32k_determine_rate(struct clk_hw *hw,
+ struct clk_rate_request *req)
+{
+ struct clk_hw *best_parent;
+ unsigned long best = 0;
+ int i, num_parents = clk_hw_get_num_parents(hw);
+
+ for (i = 0; i < num_parents; i++) {
+ struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
+ unsigned long tmp, prate = clk_hw_get_rate(parent);
+
+ tmp = ac100_clk32k_round_rate(hw, req->rate, prate);
+
+ if (tmp > req->rate)
+ continue;
+ if (req->rate - tmp < req->rate - best) {
+ best = tmp;
+ best_parent = parent;
+ }
+ }
+
+ if (!best)
+ return -EINVAL;
+
+ req->best_parent_hw = best_parent;
+ req->best_parent_rate = best;
+ req->rate = best;
+
+ return 0;
+}
+
+static int ac100_clk32k_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long prate)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+ int div = 0, pre_div = 0;
+
+ do {
+ div = divider_get_val(rate * ac100_clk32k_prediv[pre_div].div,
+ prate, NULL, AC100_CLK32K_DIV_WIDTH,
+ CLK_DIVIDER_POWER_OF_TWO);
+ if (div >= 0)
+ break;
+ } while (prate == AC100_ADDA_4M_RATE &&
+ ac100_clk32k_prediv[++pre_div].div);
+
+ if (div < 0)
+ return div;
+
+ pre_div = ac100_clk32k_prediv[pre_div].val;
+
+ regmap_update_bits(clk->regmap, clk->offset,
+ ((1 << AC100_CLK32K_DIV_WIDTH) - 1) << AC100_CLK32K_DIV_SHIFT |
+ ((1 << AC100_CLK32K_PRE_DIV_WIDTH) - 1) << AC100_CLK32K_PRE_DIV_SHIFT,
+ (div - 1) << AC100_CLK32K_DIV_SHIFT |
+ (pre_div - 1) << AC100_CLK32K_PRE_DIV_SHIFT);
+
+ return 0;
+}
+
+static int ac100_clk32k_prepare(struct clk_hw *hw)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+
+ return regmap_update_bits(clk->regmap, clk->offset, AC100_CLK32K_EN,
+ AC100_CLK32K_EN);
+}
+
+static void ac100_clk32k_unprepare(struct clk_hw *hw)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+
+ regmap_update_bits(clk->regmap, clk->offset, AC100_CLK32K_EN, 0);
+}
+
+static int ac100_clk32k_is_prepared(struct clk_hw *hw)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+ unsigned int reg;
+
+ regmap_read(clk->regmap, clk->offset, &reg);
+
+ return reg & AC100_CLK32K_EN;
+}
+
+static u8 ac100_clk32k_get_parent(struct clk_hw *hw)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+ unsigned int reg;
+
+ regmap_read(clk->regmap, clk->offset, &reg);
+
+ return (reg >> AC100_CLK32K_MUX_SHIFT) & 0x1;
+}
+
+static int ac100_clk32k_set_parent(struct clk_hw *hw, u8 index)
+{
+ struct ac100_clk32k *clk = to_ac100_clk32k(hw);
+
+ return regmap_update_bits(clk->regmap, clk->offset,
+ BIT(AC100_CLK32K_MUX_SHIFT),
+ index ? BIT(AC100_CLK32K_MUX_SHIFT) : 0);
+}
+
+static const struct clk_ops ac100_clk32k_ops = {
+ .prepare = ac100_clk32k_prepare,
+ .unprepare = ac100_clk32k_unprepare,
+ .is_prepared = ac100_clk32k_is_prepared,
+ .recalc_rate = ac100_clk32k_recalc_rate,
+ .determine_rate = ac100_clk32k_determine_rate,
+ .get_parent = ac100_clk32k_get_parent,
+ .set_parent = ac100_clk32k_set_parent,
+ .set_rate = ac100_clk32k_set_rate,
};

+static int ac100_rtc_register_clks(struct ac100_rtc_dev *chip)
+{
+ struct device_node *np = chip->dev->of_node;
+ const char *parents[2] = {AC100_RTC_32K_NAME, AC100_ADDA_4M_NAME};
+ int i, ret;
+
+ chip->clk_data = devm_kzalloc(chip->dev, sizeof(*chip->clk_data) +
+ sizeof(*chip->clk_data->hws) *
+ AC100_CLK32K_NUM,
+ GFP_KERNEL);
+ if (!chip->clk_data)
+ return -ENOMEM;
+
+ chip->rtc_32k_clk = clk_hw_register_fixed_rate(chip->dev,
+ AC100_RTC_32K_NAME,
+ NULL, 0,
+ AC100_RTC_32K_RATE);
+ if (IS_ERR(chip->rtc_32k_clk)) {
+ ret = PTR_ERR(chip->rtc_32k_clk);
+ dev_err(chip->dev, "Failed to register RTC-32k clock: %d\n",
+ ret);
+ return ret;
+ }
+
+ /*
+ * The ADDA 4 MHz clock is from the codec side of the AC100,
+ * which is likely a different power domain. However, boards
+ * always have both sides powered on, so it is impossible to
+ * test this.
+ */
+ chip->adda_4M_clk = clk_hw_register_fixed_rate(chip->dev,
+ AC100_ADDA_4M_NAME,
+ NULL, 0,
+ AC100_ADDA_4M_RATE);
+ if (IS_ERR(chip->adda_4M_clk)) {
+ ret = PTR_ERR(chip->adda_4M_clk);
+ dev_err(chip->dev, "Failed to register ADDA-4M clock: %d\n",
+ ret);
+ goto err_unregister_rtc_32k;
+ }
+
+ for (i = 0; i < AC100_CLK32K_NUM; i++) {
+ struct ac100_clk32k *clk = &chip->clks[i];
+ struct clk_init_data init = {
+ .name = ac100_clk32k_names[i],
+ .ops = &ac100_clk32k_ops,
+ .parent_names = parents,
+ .num_parents = ARRAY_SIZE(parents),
+ .flags = 0,
+ };
+
+ clk->regmap = chip->regmap;
+ clk->offset = AC100_CLK32K_OUT_CTRL1 + i;
+ clk->hw.init = &init;
+
+ ret = devm_clk_hw_register(chip->dev, &clk->hw);
+ if (ret) {
+ dev_err(chip->dev, "Failed to register clk '%s': %d\n",
+ init.name, ret);
+ goto err_unregister_adda_4M;
+ }
+
+ chip->clk_data->hws[i] = &clk->hw;
+ }
+
+ chip->clk_data->num = i;
+ ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get, chip->clk_data);
+ if (ret)
+ goto err_unregister_adda_4M;
+
+ return 0;
+
+err_unregister_adda_4M:
+ clk_unregister_fixed_rate(chip->adda_4M_clk->clk);
+err_unregister_rtc_32k:
+ clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);
+
+ return ret;
+}
+
+static void ac100_rtc_unregister_clks(struct ac100_rtc_dev *chip)
+{
+ of_clk_del_provider(chip->dev->of_node);
+ clk_unregister_fixed_rate(chip->adda_4M_clk->clk);
+ clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);
+}
+
+/**
+ * RTC related bits
+ */
static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
{
struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
@@ -349,13 +654,27 @@ static int ac100_rtc_probe(struct platform_device *pdev)
/* We do not support user interrupts */
chip->rtc->uie_unsupported = 1;

+ ret = ac100_rtc_register_clks(chip);
+ if (ret)
+ return ret;
+
dev_info(&pdev->dev, "RTC enabled\n");

return 0;
}

+static int ac100_rtc_remove(struct platform_device *pdev)
+{
+ struct ac100_rtc_dev *chip = platform_get_drvdata(pdev);
+
+ ac100_rtc_unregister_clks(chip);
+
+ return 0;
+}
+
static struct platform_driver ac100_rtc_driver = {
.probe = ac100_rtc_probe,
+ .remove = ac100_rtc_remove,
.driver = {
.name = "ac100-rtc",
},
--
2.8.1