Re: [PATCH v5 4/7] rtc: ac100: Add clk output support

From: Alexandre Belloni
Date: Fri Jul 08 2016 - 12:29:59 EST

On 08/07/2016 at 22:33:39 +0800, Chen-Yu Tsai wrote :
> 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@xxxxxxxx>
Acked-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>

> ---
> Changes since v4: none
>
> Changes since v3:
>
> - Renamed clk32k prefixes to clkout, except for the internal 32k clk
> - Changed default clk output names to "ac100-cko{1,2,3}-rtc"
> - Moved 4M ADDA clk to codec side
>
> Changes since v2: none
> Changes since v1: none
>
> ---
> drivers/rtc/rtc-ac100.c | 302 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 302 insertions(+)
>
> diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
> index 5a9ca89d04c7..70b4fd0f6122 100644
> --- a/drivers/rtc/rtc-ac100.c
> +++ b/drivers/rtc/rtc-ac100.c
> @@ -16,6 +16,7 @@
> */
>
> #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_CLKOUT_PRE_DIV_SHIFT 5
> +#define AC100_CLKOUT_PRE_DIV_WIDTH 3
> +#define AC100_CLKOUT_MUX_SHIFT 4
> +#define AC100_CLKOUT_MUX_WIDTH 1
> +#define AC100_CLKOUT_DIV_SHIFT 1
> +#define AC100_CLKOUT_DIV_WIDTH 3
> +#define AC100_CLKOUT_EN BIT(0)
> +
> /* RTC */
> #define AC100_RTC_SEC_MASK GENMASK(6, 0)
> #define AC100_RTC_MIN_MASK GENMASK(6, 0)
> @@ -67,14 +77,292 @@
> #define AC100_YEAR_MAX 2069
> #define AC100_YEAR_OFF (AC100_YEAR_MIN - 1900)
>
> +struct ac100_clkout {
> + struct clk_hw hw;
> + struct regmap *regmap;
> + u8 offset;
> +};
> +
> +#define to_ac100_clkout(_hw) container_of(_hw, struct ac100_clkout, hw)
> +
> +#define AC100_RTC_32K_NAME "ac100-rtc-32k"
> +#define AC100_RTC_32K_RATE 32768
> +#define AC100_CLKOUT_NUM 3
> +
> +static const char * const ac100_clkout_names[AC100_CLKOUT_NUM] = {
> + "ac100-cko1-rtc",
> + "ac100-cko2-rtc",
> + "ac100-cko3-rtc",
> +};
> +
> struct ac100_rtc_dev {
> struct rtc_device *rtc;
> struct device *dev;
> struct regmap *regmap;
> int irq;
> unsigned long alarm;
> +
> + struct clk_hw *rtc_32k_clk;
> + struct ac100_clkout clks[AC100_CLKOUT_NUM];
> + struct clk_hw_onecell_data *clk_data;
> };
>
> +/**
> + * Clock controls for 3 clock output pins
> + */
> +
> +static const struct clk_div_table ac100_clkout_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_clkout_recalc_rate(struct clk_hw *hw,
> + unsigned long prate)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(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_CLKOUT_PRE_DIV_SHIFT) &
> + ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1);
> + prate = divider_recalc_rate(hw, prate, div,
> + ac100_clkout_prediv, 0);
> + }
> +
> + div = (reg >> AC100_CLKOUT_DIV_SHIFT) &
> + (BIT(AC100_CLKOUT_DIV_WIDTH) - 1);
> + return divider_recalc_rate(hw, prate, div, NULL,
> + CLK_DIVIDER_POWER_OF_TWO);
> +}
> +
> +static long ac100_clkout_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_CLKOUT_DIV_WIDTH,
> + CLK_DIVIDER_POWER_OF_TWO);
> +
> + for (i = 0; ac100_clkout_prediv[i].div; i++) {
> + tmp_prate = DIV_ROUND_UP(prate, ac100_clkout_prediv[i].val);
> + tmp_rate = divider_round_rate(hw, rate, &tmp_prate, NULL,
> + AC100_CLKOUT_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_clkout_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_clkout_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_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long prate)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(hw);
> + int div = 0, pre_div = 0;
> +
> + do {
> + div = divider_get_val(rate * ac100_clkout_prediv[pre_div].div,
> + prate, NULL, AC100_CLKOUT_DIV_WIDTH,
> + CLK_DIVIDER_POWER_OF_TWO);
> + if (div >= 0)
> + break;
> + } while (prate != AC100_RTC_32K_RATE &&
> + ac100_clkout_prediv[++pre_div].div);
> +
> + if (div < 0)
> + return div;
> +
> + pre_div = ac100_clkout_prediv[pre_div].val;
> +
> + regmap_update_bits(clk->regmap, clk->offset,
> + ((1 << AC100_CLKOUT_DIV_WIDTH) - 1) << AC100_CLKOUT_DIV_SHIFT |
> + ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1) << AC100_CLKOUT_PRE_DIV_SHIFT,
> + (div - 1) << AC100_CLKOUT_DIV_SHIFT |
> + (pre_div - 1) << AC100_CLKOUT_PRE_DIV_SHIFT);
> +
> + return 0;
> +}
> +
> +static int ac100_clkout_prepare(struct clk_hw *hw)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(hw);
> +
> + return regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN,
> + AC100_CLKOUT_EN);
> +}
> +
> +static void ac100_clkout_unprepare(struct clk_hw *hw)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(hw);
> +
> + regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN, 0);
> +}
> +
> +static int ac100_clkout_is_prepared(struct clk_hw *hw)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(hw);
> + unsigned int reg;
> +
> + regmap_read(clk->regmap, clk->offset, &reg);
> +
> + return reg & AC100_CLKOUT_EN;
> +}
> +
> +static u8 ac100_clkout_get_parent(struct clk_hw *hw)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(hw);
> + unsigned int reg;
> +
> + regmap_read(clk->regmap, clk->offset, &reg);
> +
> + return (reg >> AC100_CLKOUT_MUX_SHIFT) & 0x1;
> +}
> +
> +static int ac100_clkout_set_parent(struct clk_hw *hw, u8 index)
> +{
> + struct ac100_clkout *clk = to_ac100_clkout(hw);
> +
> + return regmap_update_bits(clk->regmap, clk->offset,
> + BIT(AC100_CLKOUT_MUX_SHIFT),
> + index ? BIT(AC100_CLKOUT_MUX_SHIFT) : 0);
> +}
> +
> +static const struct clk_ops ac100_clkout_ops = {
> + .prepare = ac100_clkout_prepare,
> + .unprepare = ac100_clkout_unprepare,
> + .is_prepared = ac100_clkout_is_prepared,
> + .recalc_rate = ac100_clkout_recalc_rate,
> + .determine_rate = ac100_clkout_determine_rate,
> + .get_parent = ac100_clkout_get_parent,
> + .set_parent = ac100_clkout_set_parent,
> + .set_rate = ac100_clkout_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};
> + int i, ret;
> +
> + chip->clk_data = devm_kzalloc(chip->dev, sizeof(*chip->clk_data) +
> + sizeof(*chip->clk_data->hws) *
> + AC100_CLKOUT_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;
> + }
> +
> + parents[1] = of_clk_get_parent_name(np, 0);
> + if (!parents[1]) {
> + dev_err(chip->dev, "Failed to get ADDA 4M clock\n");
> + return -EINVAL;
> + }
> +
> + for (i = 0; i < AC100_CLKOUT_NUM; i++) {
> + struct ac100_clkout *clk = &chip->clks[i];
> + struct clk_init_data init = {
> + .name = ac100_clkout_names[i],
> + .ops = &ac100_clkout_ops,
> + .parent_names = parents,
> + .num_parents = ARRAY_SIZE(parents),
> + .flags = 0,
> + };
> +
> + clk->regmap = chip->regmap;
> + clk->offset = AC100_CLKOUT_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_rtc_32k;
> + }
> +
> + 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_rtc_32k;
> +
> + return 0;
> +
> +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->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);
> @@ -300,11 +588,24 @@ static int ac100_rtc_probe(struct platform_device *pdev)
> return PTR_ERR(chip->rtc);
> }
>
> + 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 const struct of_device_id ac100_rtc_match[] = {
> { .compatible = "x-powers,ac100-rtc" },
> { },
> @@ -313,6 +614,7 @@ MODULE_DEVICE_TABLE(of, ac100_rtc_match);
>
> static struct platform_driver ac100_rtc_driver = {
> .probe = ac100_rtc_probe,
> + .remove = ac100_rtc_remove,
> .driver = {
> .name = "ac100-rtc",
> .of_match_table = of_match_ptr(ac100_rtc_match),
> --
> 2.8.1
>

--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com