[PATCH v5 2/2] power: reset: at91-shdwc: add new shutdown controller driver

[Nicolas Ferre <nicolas.ferre@atmel.com>]

Sama5d2 SoC has a completely new shutdown controller with new features and
register layout. It thus makes sense to add a new driver for this new
peripheral.

This driver is Device Tree only and handles events from the wake-up pin and
the RTC.
As the register layout may change in the future, so some values are encoded
in a configuration structure.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---

Changes in v5:
- Instead of the "alternate shdwc" we choose a more specific
  "sama5d2-compatible shdwc" wording. Change file name, in Kconfig, and the
  MAINTAINERS file:
  at91-shdwc.c -> at91-sama5d2_shdwc.c
  "ATMEL AT91 Alternative Shutdown Controller" -> "ATMEL AT91 SAMA5D2-Compatible
  Shutdown Controller"
- fix one indentation mismatch

Changes in v4:
- fix warning found by 0-day robot: large integer implicitly truncated to
  unsigned type [-Woverflow]
- move to the property debounce-delay-us
- move to atmel,wakeup-active-high boolean
- add entry in MAINTAINERS file

Changes in v3:
- add the slow clock handle as the IP uses it
- remove useless protection at the beginning of pm_power_off handler
- allow to compile it as a module
- add COMPILE_TEST directive in Kconfig
- update description in file header

Changes in v2:
- add MODULE_DEVICE_TABLE as advised by Sebastian Reichel
- review indentation and braces to correct errors pointed out by checkpatch

 MAINTAINERS                              |   5 +
 drivers/power/reset/Kconfig              |   8 +
 drivers/power/reset/Makefile             |   1 +
 drivers/power/reset/at91-sama5d2_shdwc.c | 282 +++++++++++++++++++++++++++++++
 4 files changed, 296 insertions(+)
 create mode 100644 drivers/power/reset/at91-sama5d2_shdwc.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 5744af3d79ab..a05b14d8d4d2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1999,6 +1999,11 @@ M:	Nicolas Ferre <nicolas.ferre@atmel.com>
 S:	Supported
 F:	drivers/tty/serial/atmel_serial.c
 
+ATMEL AT91 SAMA5D2-Compatible Shutdown Controller
+M:	Nicolas Ferre <nicolas.ferre@atmel.com>
+S:	Supported
+F:	drivers/power/reset/at91-sama5d2_shdwc.c
+
 ATMEL SAMA5D2 ADC DRIVER
 M:	Ludovic Desroches <ludovic.desroches@atmel.com>
 L:	linux-iio@vger.kernel.org
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index 0a6408a39c66..9bb2622c23bf 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -30,6 +30,14 @@ config POWER_RESET_AT91_RESET
 	  This driver supports restart for Atmel AT91SAM9 and SAMA5
 	  SoCs
 
+config POWER_RESET_AT91_SAMA5D2_SHDWC
+	tristate "Atmel AT91 SAMA5D2-Compatible shutdown controller driver"
+	depends on ARCH_AT91 || COMPILE_TEST
+	default SOC_SAMA5
+	help
+	  This driver supports the alternate shutdown controller for some Atmel
+	  SAMA5 SoCs. It is present for example on SAMA5D2 SoC.
+
 config POWER_RESET_AXXIA
 	bool "LSI Axxia reset driver"
 	depends on ARCH_AXXIA
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 096fa67047f6..ab7aa8614d1f 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -1,6 +1,7 @@
 obj-$(CONFIG_POWER_RESET_AS3722) += as3722-poweroff.o
 obj-$(CONFIG_POWER_RESET_AT91_POWEROFF) += at91-poweroff.o
 obj-$(CONFIG_POWER_RESET_AT91_RESET) += at91-reset.o
+obj-$(CONFIG_POWER_RESET_AT91_SAMA5D2_SHDWC) += at91-sama5d2_shdwc.o
 obj-$(CONFIG_POWER_RESET_AXXIA) += axxia-reset.o
 obj-$(CONFIG_POWER_RESET_BRCMSTB) += brcmstb-reboot.o
 obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
diff --git a/drivers/power/reset/at91-sama5d2_shdwc.c b/drivers/power/reset/at91-sama5d2_shdwc.c
new file mode 100644
index 000000000000..8a5ac9706c9c
--- /dev/null
+++ b/drivers/power/reset/at91-sama5d2_shdwc.c
@@ -0,0 +1,282 @@
+/*
+ * Atmel SAMA5D2-Compatible Shutdown Controller (SHDWC) driver.
+ * Found on some SoCs as the sama5d2 (obviously).
+ *
+ * Copyright (C) 2015 Atmel Corporation,
+ *                    Nicolas Ferre <nicolas.ferre@atmel.com>
+ *
+ * Evolved from driver at91-poweroff.c.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ *
+ * TODO:
+ * - addition to status of other wake-up inputs [1 - 15]
+ * - Analog Comparator wake-up alarm
+ * - Serial RX wake-up alarm
+ * - low power debouncer
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+
+#define SLOW_CLOCK_FREQ	32768
+
+#define AT91_SHDW_CR	0x00		/* Shut Down Control Register */
+#define AT91_SHDW_SHDW		BIT(0)			/* Shut Down command */
+#define AT91_SHDW_KEY		(0xa5UL << 24)		/* KEY Password */
+
+#define AT91_SHDW_MR	0x04		/* Shut Down Mode Register */
+#define AT91_SHDW_WKUPDBC_SHIFT	24
+#define AT91_SHDW_WKUPDBC_MASK	GENMASK(31, 16)
+#define AT91_SHDW_WKUPDBC(x)	(((x) << AT91_SHDW_WKUPDBC_SHIFT) \
+						& AT91_SHDW_WKUPDBC_MASK)
+
+#define AT91_SHDW_SR	0x08		/* Shut Down Status Register */
+#define AT91_SHDW_WKUPIS_SHIFT	16
+#define AT91_SHDW_WKUPIS_MASK	GENMASK(31, 16)
+#define AT91_SHDW_WKUPIS(x)	((1 << (x)) << AT91_SHDW_WKUPIS_SHIFT \
+						& AT91_SHDW_WKUPIS_MASK)
+
+#define AT91_SHDW_WUIR	0x0c		/* Shutdown Wake-up Inputs Register */
+#define AT91_SHDW_WKUPEN_MASK	GENMASK(15, 0)
+#define AT91_SHDW_WKUPEN(x)	((1 << (x)) & AT91_SHDW_WKUPEN_MASK)
+#define AT91_SHDW_WKUPT_SHIFT	16
+#define AT91_SHDW_WKUPT_MASK	GENMASK(31, 16)
+#define AT91_SHDW_WKUPT(x)	((1 << (x)) << AT91_SHDW_WKUPT_SHIFT \
+						& AT91_SHDW_WKUPT_MASK)
+
+#define SHDW_WK_PIN(reg, cfg)	((reg) & AT91_SHDW_WKUPIS((cfg)->wkup_pin_input))
+#define SHDW_RTCWK(reg, cfg)	(((reg) >> ((cfg)->sr_rtcwk_shift)) & 0x1)
+#define SHDW_RTCWKEN(cfg)	(1 << ((cfg)->mr_rtcwk_shift))
+
+#define DBC_PERIOD_US(x)	DIV_ROUND_UP_ULL((1000000 * (x)), \
+							SLOW_CLOCK_FREQ)
+
+struct shdwc_config {
+	u8 wkup_pin_input;
+	u8 mr_rtcwk_shift;
+	u8 sr_rtcwk_shift;
+};
+
+struct shdwc {
+	struct shdwc_config *cfg;
+	void __iomem *at91_shdwc_base;
+};
+
+/*
+ * Hold configuration here, cannot be more than one instance of the driver
+ * since pm_power_off itself is global.
+ */
+static struct shdwc *at91_shdwc;
+static struct clk *sclk;
+
+static const unsigned long long sdwc_dbc_period[] = {
+	0, 3, 32, 512, 4096, 32768,
+};
+
+static void __init at91_wakeup_status(struct platform_device *pdev)
+{
+	struct shdwc *shdw = platform_get_drvdata(pdev);
+	u32 reg;
+	char *reason = "unknown";
+
+	reg = readl(shdw->at91_shdwc_base + AT91_SHDW_SR);
+
+	dev_dbg(&pdev->dev, "%s: status = %#x\n", __func__, reg);
+
+	/* Simple power-on, just bail out */
+	if (!reg)
+		return;
+
+	if (SHDW_WK_PIN(reg, shdw->cfg))
+		reason = "WKUP pin";
+	else if (SHDW_RTCWK(reg, shdw->cfg))
+		reason = "RTC";
+
+	pr_info("AT91: Wake-Up source: %s\n", reason);
+}
+
+static void at91_poweroff(void)
+{
+	writel(AT91_SHDW_KEY | AT91_SHDW_SHDW,
+	       at91_shdwc->at91_shdwc_base + AT91_SHDW_CR);
+}
+
+static u32 at91_shdwc_debouncer_value(struct platform_device *pdev,
+				      u32 in_period_us)
+{
+	int i;
+	int max_idx = ARRAY_SIZE(sdwc_dbc_period) - 1;
+	unsigned long long period_us;
+	unsigned long long max_period_us = DBC_PERIOD_US(sdwc_dbc_period[max_idx]);
+
+	if (in_period_us > max_period_us) {
+		dev_warn(&pdev->dev,
+			 "debouncer period %u too big, reduced to %llu us\n",
+			 in_period_us, max_period_us);
+		return max_idx;
+	}
+
+	for (i = max_idx - 1; i > 0; i--) {
+		period_us = DBC_PERIOD_US(sdwc_dbc_period[i]);
+		dev_dbg(&pdev->dev, "%s: ref[%d] = %llu\n",
+						__func__, i, period_us);
+		if (in_period_us > period_us)
+			break;
+	}
+
+	return i + 1;
+}
+
+static u32 at91_shdwc_get_wakeup_input(struct platform_device *pdev,
+				       struct device_node *np)
+{
+	struct device_node *cnp;
+	u32 wk_input_mask;
+	u32 wuir = 0;
+	u32 wk_input;
+
+	for_each_child_of_node(np, cnp) {
+		if (of_property_read_u32(cnp, "reg", &wk_input)) {
+			dev_warn(&pdev->dev, "reg property is missing for %s\n",
+				 cnp->full_name);
+			continue;
+		}
+
+		wk_input_mask = 1 << wk_input;
+		if (!(wk_input_mask & AT91_SHDW_WKUPEN_MASK)) {
+			dev_warn(&pdev->dev,
+				 "wake-up input %d out of bounds ignore\n",
+				 wk_input);
+			continue;
+		}
+		wuir |= wk_input_mask;
+
+		if (of_property_read_bool(cnp, "atmel,wakeup-active-high"))
+			wuir |= AT91_SHDW_WKUPT(wk_input);
+
+		dev_dbg(&pdev->dev, "%s: (child %d) wuir = %#x\n",
+						__func__, wk_input, wuir);
+	}
+
+	return wuir;
+}
+
+static void at91_shdwc_dt_configure(struct platform_device *pdev)
+{
+	struct shdwc *shdw = platform_get_drvdata(pdev);
+	struct device_node *np = pdev->dev.of_node;
+	u32 mode = 0, tmp, input;
+
+	if (!np) {
+		dev_err(&pdev->dev, "device node not found\n");
+		return;
+	}
+
+	if (!of_property_read_u32(np, "debounce-delay-us", &tmp))
+		mode |= AT91_SHDW_WKUPDBC(at91_shdwc_debouncer_value(pdev, tmp));
+
+	if (of_property_read_bool(np, "atmel,wakeup-rtc-timer"))
+		mode |= SHDW_RTCWKEN(shdw->cfg);
+
+	dev_dbg(&pdev->dev, "%s: mode = %#x\n", __func__, mode);
+	writel(mode, shdw->at91_shdwc_base + AT91_SHDW_MR);
+
+	input = at91_shdwc_get_wakeup_input(pdev, np);
+	writel(input, shdw->at91_shdwc_base + AT91_SHDW_WUIR);
+}
+
+static const struct shdwc_config sama5d2_shdwc_config = {
+	.wkup_pin_input = 0,
+	.mr_rtcwk_shift = 17,
+	.sr_rtcwk_shift = 5,
+};
+
+static const struct of_device_id at91_shdwc_of_match[] = {
+	{
+		.compatible = "atmel,sama5d2-shdwc",
+		.data = &sama5d2_shdwc_config,
+	}, {
+		/*sentinel*/
+	}
+};
+MODULE_DEVICE_TABLE(of, at91_shdwc_of_match);
+
+static int __init at91_shdwc_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	const struct of_device_id *match;
+	int ret;
+
+	if (!pdev->dev.of_node)
+		return -ENODEV;
+
+	at91_shdwc = devm_kzalloc(&pdev->dev, sizeof(*at91_shdwc), GFP_KERNEL);
+	if (!at91_shdwc)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, at91_shdwc);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	at91_shdwc->at91_shdwc_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(at91_shdwc->at91_shdwc_base)) {
+		dev_err(&pdev->dev, "Could not map reset controller address\n");
+		return PTR_ERR(at91_shdwc->at91_shdwc_base);
+	}
+
+	match = of_match_node(at91_shdwc_of_match, pdev->dev.of_node);
+	at91_shdwc->cfg = (struct shdwc_config *)(match->data);
+
+	sclk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(sclk))
+		return PTR_ERR(sclk);
+
+	ret = clk_prepare_enable(sclk);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not enable slow clock\n");
+		return ret;
+	}
+
+	at91_wakeup_status(pdev);
+
+	at91_shdwc_dt_configure(pdev);
+
+	pm_power_off = at91_poweroff;
+
+	return 0;
+}
+
+static int __exit at91_shdwc_remove(struct platform_device *pdev)
+{
+	struct shdwc *shdw = platform_get_drvdata(pdev);
+
+	if (pm_power_off == at91_poweroff)
+		pm_power_off = NULL;
+
+	/* Reset values to disable wake-up features  */
+	writel(0, shdw->at91_shdwc_base + AT91_SHDW_MR);
+	writel(0, shdw->at91_shdwc_base + AT91_SHDW_WUIR);
+
+	clk_disable_unprepare(sclk);
+
+	return 0;
+}
+
+static struct platform_driver at91_shdwc_driver = {
+	.remove = __exit_p(at91_shdwc_remove),
+	.driver = {
+		.name = "at91-shdwc",
+		.of_match_table = at91_shdwc_of_match,
+	},
+};
+module_platform_driver_probe(at91_shdwc_driver, at91_shdwc_probe);
+
+MODULE_AUTHOR("Nicolas Ferre <nicolas.ferre@atmel.com>");
+MODULE_DESCRIPTION("Atmel shutdown controller driver");
+MODULE_LICENSE("GPL v2");
-- 
2.1.3