[PATCH v1 2/2] ptp: Add a ptp clock driver for Broadcom DTE

[Arun Parameswaran <arun.parameswaran@broadcom.com>]

This patch adds a ptp clock driver for the Broadcom SoCs using
the Digital timing Engine (DTE) nco.

Signed-off-by: Arun Parameswaran <arun.parameswaran@broadcom.com>
---
 drivers/ptp/Kconfig   |  16 +++
 drivers/ptp/Makefile  |   1 +
 drivers/ptp/ptp_dte.c | 353 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 370 insertions(+)
 create mode 100644 drivers/ptp/ptp_dte.c

diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index 384f661..a21ad10 100644
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -25,6 +25,22 @@ config PTP_1588_CLOCK
 	  To compile this driver as a module, choose M here: the module
 	  will be called ptp.
 
+config PTP_1588_CLOCK_DTE
+	tristate "Broadcom DTE as PTP clock"
+	depends on PTP_1588_CLOCK
+	depends on NET && HAS_IOMEM
+	depends on ARCH_BCM_MOBILE || (ARCH_BCM_IPROC && !(ARCH_BCM_NSP || ARCH_BCM_5301X)) || COMPILE_TEST
+	default y
+	help
+	  This driver adds support for using the Digital timing engine
+	  (DTE) in the Broadcom SoC's as a PTP clock.
+
+	  The clock can be used in both wired and wireless networks
+	  for PTP purposes.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ptp_dte.
+
 config PTP_1588_CLOCK_GIANFAR
 	tristate "Freescale eTSEC as PTP clock"
 	depends on GIANFAR
diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
index 5307361..d1f2fb1 100644
--- a/drivers/ptp/Makefile
+++ b/drivers/ptp/Makefile
@@ -4,6 +4,7 @@
 
 ptp-y					:= ptp_clock.o ptp_chardev.o ptp_sysfs.o
 obj-$(CONFIG_PTP_1588_CLOCK)		+= ptp.o
+obj-$(CONFIG_PTP_1588_CLOCK_DTE)	+= ptp_dte.o
 obj-$(CONFIG_PTP_1588_CLOCK_IXP46X)	+= ptp_ixp46x.o
 obj-$(CONFIG_PTP_1588_CLOCK_PCH)	+= ptp_pch.o
 obj-$(CONFIG_PTP_1588_CLOCK_KVM)	+= ptp_kvm.o
diff --git a/drivers/ptp/ptp_dte.c b/drivers/ptp/ptp_dte.c
new file mode 100644
index 0000000..00145a3
--- /dev/null
+++ b/drivers/ptp/ptp_dte.c
@@ -0,0 +1,353 @@
+/*
+ * Copyright 2017 Broadcom
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/ptp_clock_kernel.h>
+#include <linux/types.h>
+
+#define DTE_NCO_LOW_TIME_REG	0x00
+#define DTE_NCO_TIME_REG	0x04
+#define DTE_NCO_OVERFLOW_REG	0x08
+#define DTE_NCO_INC_REG		0x0c
+
+#define DTE_NCO_SUM2_MASK	0xffffffff
+#define DTE_NCO_SUM2_SHIFT	4ULL
+
+#define DTE_NCO_SUM3_MASK	0xff
+#define DTE_NCO_SUM3_SHIFT	36ULL
+#define DTE_NCO_SUM3_WR_SHIFT	8
+
+#define DTE_NCO_TS_WRAP_MASK	0xfff
+#define DTE_NCO_TS_WRAP_LSHIFT	32
+
+#define DTE_NCO_INC_DEFAULT	0x80000000
+#define DTE_NUM_REGS_TO_RESTORE	4
+
+/* Full wrap around is 44bits in ns (~4.887 hrs) */
+#define DTE_WRAP_AROUND_NSEC_SHIFT 44
+
+/* 44 bits NCO */
+#define DTE_NCO_MAX_NS	0xFFFFFFFFFFF
+
+/* 125MHz with 3.29 reg cfg */
+#define DTE_PPB_ADJ(ppb) (u32)(div64_u64((((u64)abs(ppb) * BIT(28)) +\
+				      62500000ULL), 125000000ULL))
+
+/* ptp dte priv structure */
+struct ptp_dte {
+	void __iomem *regs;
+	struct ptp_clock *ptp_clk;
+	struct ptp_clock_info caps;
+	struct device *dev;
+	u32 ts_ovf_last;
+	u32 ts_wrap_cnt;
+	spinlock_t lock;
+	u32 reg_val[DTE_NUM_REGS_TO_RESTORE];
+};
+
+static void dte_write_nco(void __iomem *regs, s64 ns)
+{
+	u32 sum2, sum3;
+
+	sum2 = (u32)((ns >> DTE_NCO_SUM2_SHIFT) & DTE_NCO_SUM2_MASK);
+	/* compensate for ignoring sum1 */
+	if (sum2 != DTE_NCO_SUM2_MASK)
+		sum2++;
+
+	/* to write sum3, bits [15:8] needs to be written */
+	sum3 = (u32)(((ns >> DTE_NCO_SUM3_SHIFT) & DTE_NCO_SUM3_MASK) <<
+		     DTE_NCO_SUM3_WR_SHIFT);
+
+	writel(0, (regs + DTE_NCO_LOW_TIME_REG));
+	writel(sum2, (regs + DTE_NCO_TIME_REG));
+	writel(sum3, (regs + DTE_NCO_OVERFLOW_REG));
+}
+
+static s64 dte_read_nco(void __iomem *regs)
+{
+	u32 sum2, sum3;
+	s64 ns;
+
+	/*
+	 * ignoring sum1 (4 bits) gives a 16ns resolution, which
+	 * works due to the async register read.
+	 */
+	sum3 = readl(regs + DTE_NCO_OVERFLOW_REG) & DTE_NCO_SUM3_MASK;
+	sum2 = readl(regs + DTE_NCO_TIME_REG);
+	ns = ((s64)sum3 << DTE_NCO_SUM3_SHIFT) |
+		 ((s64)sum2 << DTE_NCO_SUM2_SHIFT);
+
+	return ns;
+}
+
+static void dte_write_nco_delta(struct ptp_dte *ptp_dte, s64 delta)
+{
+	s64 ns;
+
+	ns = dte_read_nco(ptp_dte->regs);
+
+	/* handle wraparound conditions */
+	if ((delta < 0) && (abs(delta) > ns)) {
+		if (ptp_dte->ts_wrap_cnt) {
+			ns += DTE_NCO_MAX_NS + delta;
+			ptp_dte->ts_wrap_cnt--;
+		} else {
+			ns = 0;
+		}
+	} else {
+		ns += delta;
+		if (ns > DTE_NCO_MAX_NS) {
+			ptp_dte->ts_wrap_cnt++;
+			ns -= DTE_NCO_MAX_NS;
+		}
+	}
+
+	dte_write_nco(ptp_dte->regs, ns);
+
+	ptp_dte->ts_ovf_last = (ns >> DTE_NCO_TS_WRAP_LSHIFT) &
+			DTE_NCO_TS_WRAP_MASK;
+}
+
+static s64 dte_read_nco_with_ovf(struct ptp_dte *ptp_dte)
+{
+	u32 ts_ovf;
+	s64 ns = 0;
+
+	ns = dte_read_nco(ptp_dte->regs);
+
+	/*Timestamp overflow: 8 LSB bits of sum3, 4 MSB bits of sum2 */
+	ts_ovf = (ns >> DTE_NCO_TS_WRAP_LSHIFT) & DTE_NCO_TS_WRAP_MASK;
+
+	/* Check for wrap around */
+	if (ts_ovf < ptp_dte->ts_ovf_last)
+		ptp_dte->ts_wrap_cnt++;
+
+	ptp_dte->ts_ovf_last = ts_ovf;
+
+	/* adjust for wraparounds */
+	ns += (s64)(BIT_ULL(DTE_WRAP_AROUND_NSEC_SHIFT) * ptp_dte->ts_wrap_cnt);
+
+	return ns;
+}
+
+static int ptp_dte_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
+{
+	u32 nco_incr;
+	unsigned long flags;
+	struct ptp_dte *ptp_dte = container_of(ptp, struct ptp_dte, caps);
+
+	if (abs(ppb) > ptp_dte->caps.max_adj) {
+		dev_err(ptp_dte->dev, "ppb adj too big\n");
+		return -EINVAL;
+	}
+
+	if (ppb < 0)
+		nco_incr = DTE_NCO_INC_DEFAULT - DTE_PPB_ADJ(ppb);
+	else
+		nco_incr = DTE_NCO_INC_DEFAULT + DTE_PPB_ADJ(ppb);
+
+	spin_lock_irqsave(&ptp_dte->lock, flags);
+	writel(nco_incr, ptp_dte->regs + DTE_NCO_INC_REG);
+	spin_unlock_irqrestore(&ptp_dte->lock, flags);
+
+	return 0;
+}
+
+static int ptp_dte_adjtime(struct ptp_clock_info *ptp, s64 delta)
+{
+	unsigned long flags;
+	struct ptp_dte *ptp_dte = container_of(ptp, struct ptp_dte, caps);
+
+	spin_lock_irqsave(&ptp_dte->lock, flags);
+	dte_write_nco_delta(ptp_dte, delta);
+	spin_unlock_irqrestore(&ptp_dte->lock, flags);
+
+	return 0;
+}
+
+static int ptp_dte_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
+{
+	unsigned long flags;
+	struct ptp_dte *ptp_dte = container_of(ptp, struct ptp_dte, caps);
+
+	spin_lock_irqsave(&ptp_dte->lock, flags);
+	*ts = ns_to_timespec64(dte_read_nco_with_ovf(ptp_dte));
+	spin_unlock_irqrestore(&ptp_dte->lock, flags);
+
+	return 0;
+}
+
+static int ptp_dte_settime(struct ptp_clock_info *ptp,
+			     const struct timespec64 *ts)
+{
+	unsigned long flags;
+	struct ptp_dte *ptp_dte = container_of(ptp, struct ptp_dte, caps);
+
+	spin_lock_irqsave(&ptp_dte->lock, flags);
+
+	/* Disable nco increment */
+	writel(0, ptp_dte->regs + DTE_NCO_INC_REG);
+
+	dte_write_nco(ptp_dte->regs, timespec64_to_ns(ts));
+
+	/* reset overflow and wrap counter */
+	ptp_dte->ts_ovf_last = 0;
+	ptp_dte->ts_wrap_cnt = 0;
+
+	/* Enable nco increment */
+	writel(DTE_NCO_INC_DEFAULT, ptp_dte->regs + DTE_NCO_INC_REG);
+
+	spin_unlock_irqrestore(&ptp_dte->lock, flags);
+
+	return 0;
+}
+
+static int ptp_dte_enable(struct ptp_clock_info *ptp,
+			    struct ptp_clock_request *rq, int on)
+{
+	return -EOPNOTSUPP;
+}
+
+static struct ptp_clock_info ptp_dte_caps = {
+	.owner		= THIS_MODULE,
+	.name		= "DTE PTP timer",
+	.max_adj	= 50000000,
+	.n_ext_ts	= 0,
+	.n_pins		= 0,
+	.pps		= 0,
+	.adjfreq	= ptp_dte_adjfreq,
+	.adjtime	= ptp_dte_adjtime,
+	.gettime64	= ptp_dte_gettime,
+	.settime64	= ptp_dte_settime,
+	.enable		= ptp_dte_enable,
+};
+
+static int ptp_dte_probe(struct platform_device *pdev)
+{
+	struct ptp_dte *ptp_dte;
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+
+	ptp_dte = devm_kzalloc(dev, sizeof(struct ptp_dte), GFP_KERNEL);
+	if (!ptp_dte)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	ptp_dte->regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(ptp_dte->regs)) {
+		dev_err(dev,
+			"%s: io remap failed\n", __func__);
+		return PTR_ERR(ptp_dte->regs);
+	}
+
+	spin_lock_init(&ptp_dte->lock);
+
+	ptp_dte->dev = dev;
+	ptp_dte->caps = ptp_dte_caps;
+	ptp_dte->ptp_clk = ptp_clock_register(&ptp_dte->caps, &pdev->dev);
+	if (IS_ERR(ptp_dte->ptp_clk)) {
+		dev_err(dev,
+			"%s: Failed to register ptp clock\n", __func__);
+		return PTR_ERR(ptp_dte->ptp_clk);
+	}
+
+	platform_set_drvdata(pdev, ptp_dte);
+
+	dev_info(dev, "ptp clk probe done\n");
+
+	return 0;
+}
+
+static int ptp_dte_remove(struct platform_device *pdev)
+{
+	struct ptp_dte *ptp_dte = platform_get_drvdata(pdev);
+	u8 i;
+
+	ptp_clock_unregister(ptp_dte->ptp_clk);
+
+	for (i = 0; i < DTE_NUM_REGS_TO_RESTORE; i++)
+		writel(0, ptp_dte->regs + (i * sizeof(u32)));
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int ptp_dte_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct ptp_dte *ptp_dte = platform_get_drvdata(pdev);
+	u8 i;
+
+	for (i = 0; i < DTE_NUM_REGS_TO_RESTORE; i++) {
+		ptp_dte->reg_val[i] =
+			readl(ptp_dte->regs + (i * sizeof(u32)));
+	}
+
+	/* disable the nco */
+	writel(0, ptp_dte->regs + DTE_NCO_INC_REG);
+
+	return 0;
+}
+
+static int ptp_dte_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct ptp_dte *ptp_dte = platform_get_drvdata(pdev);
+	u8 i;
+
+	for (i = 0; i < DTE_NUM_REGS_TO_RESTORE; i++) {
+		if ((i * sizeof(u32)) != DTE_NCO_OVERFLOW_REG)
+			writel(ptp_dte->reg_val[i],
+				(ptp_dte->regs + (i * sizeof(u32))));
+		else
+			writel(((ptp_dte->reg_val[i] &
+				DTE_NCO_SUM3_MASK) << DTE_NCO_SUM3_WR_SHIFT),
+				(ptp_dte->regs + (i * sizeof(u32))));
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops ptp_dte_pm_ops = {
+	.suspend = ptp_dte_suspend,
+	.resume = ptp_dte_resume
+};
+
+#define PTP_DTE_PM_OPS	(&ptp_dte_pm_ops)
+#else
+#define PTP_DTE_PM_OPS	NULL
+#endif
+
+static const struct of_device_id ptp_dte_of_match[] = {
+	{ .compatible = "brcm,ptp-dte", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ptp_dte_of_match);
+
+static struct platform_driver ptp_dte_driver = {
+	.driver = {
+		.name = "ptp-dte",
+		.pm = PTP_DTE_PM_OPS,
+		.of_match_table = ptp_dte_of_match,
+	},
+	.probe    = ptp_dte_probe,
+	.remove   = ptp_dte_remove,
+};
+module_platform_driver(ptp_dte_driver);
+
+MODULE_AUTHOR("Broadcom");
+MODULE_DESCRIPTION("Broadcom DTE PTP Clock driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1