clocksource: davinci-timer: new driver

From: Bartosz Golaszewski <[email protected]>

Now that we have an agreement on the driver and only minor issues are left to fix, I'm dropping the RFC tag and continuing the numbering from before RFCs.

This is the davinci clocksource driver but it with a sparse warning fixed and with a small tweak to kzalloc() call.

RFC history:

v1 -> v2:
- changed the format of the copyright notice
- removed all mentiones of the periodic timer setting
- added caching of the TCR register value so that its updating doesn't require a read
- split the timer configuration for clock events into the set_state_oneshot() and set_state_shutdown() callbacks

v2 -> v3:
- tim34, if used, should run in periodic mode for clocksource, now fixed
- dropped all the configuration variables from struct davinci_clockevent as clockevent always uses tim12
- dropped caching of the TCR register with the following reasoning: on systems using tim34 for clocksource, the TCR register is only touched by the clock driver and we know that we need to keep tim34 in periodic mode; on da830 the RTOS running on the DSP may modify the TCR register but we on the other hand never change its settings when only using tim12
- subsequently the whole routine for TCR updating was dropped
- dropped the shift variable from most places
- added separate routines for initializing clocksource for da830 and all other systems
- sprinkled a bunch of comments all over the driver to explain things that caused confusion before

Changes since last RFC:

- fixed the following sparse warning:

- added the __GFP_NOFAIL flag to kzalloc() call so that we don't get warnings about not freeing the memory later

Bartosz Golaszewski (2):
clocksource: davinci-timer: add support for clockevents
clocksource: timer-davinci: add support for clocksource

 drivers/clocksource/Kconfig         |   5 +
 drivers/clocksource/Makefile        |   1 +
 drivers/clocksource/timer-davinci.c | 369 ++++++++++++++++++++++++++++
 include/clocksource/timer-davinci.h |  44 ++++
 4 files changed, 419 insertions(+)
 create mode 100644 drivers/clocksource/timer-davinci.c
 create mode 100644 include/clocksource/timer-davinci.h

2.21.0

From: Bartosz Golaszewski <[email protected]>

Currently the clocksource and clockevent support for davinci platforms lives in mach-davinci. It hard-codes many things, uses global variables, implements functionalities unused by any platform and has code fragments scattered across many (often unrelated) files.

Implement a new, modern and simplified timer driver and put it into drivers/clocksource. We still need to support legacy board files so export a config structure and a function that allows machine code to register the timer.

The timer we're using is 64-bit but can be programmed in dual 32-bit mode (both chained and unchained).

On all davinci SoCs except for da830 we're using both halves. Lower half for clockevents and upper half for clocksource. On da830 we're using the lower half for both with the help of a compare register.

This patch contains the core code and support for clockevent. The clocksource code will be included in a subsequent patch.

---
 drivers/clocksource/Kconfig         |   5 +
 drivers/clocksource/Makefile        |   1 +
 drivers/clocksource/timer-davinci.c | 284 ++++++++++++++++++++++++++++
 include/clocksource/timer-davinci.h |  44 +++++
 4 files changed, 334 insertions(+)
 create mode 100644 drivers/clocksource/timer-davinci.c
 create mode 100644 include/clocksource/timer-davinci.h

index 3300739edce4..6717a09500ab 100644
@@ -43,6 +43,11 @@ config BCM_KONA_TIMER
 	help
 	  Enables the support for the BCM Kona mobile timer driver.
 
+config DAVINCI_TIMER
+	bool "Texas Instruments DaVinci timer driver" if COMPILE_TEST
+	help
+	  Enables the support for the TI DaVinci timer driver.
+
 config DIGICOLOR_TIMER
 	bool "Digicolor timer driver" if COMPILE_TEST
 	select CLKSRC_MMIO

index 236858fa7fbf..021831bcc567 100644
@@ -15,6 +15,7 @@ obj-$(CONFIG_SH_TIMER_TMU)	+= sh_tmu.o
 obj-$(CONFIG_EM_TIMER_STI)	+= em_sti.o
 obj-$(CONFIG_CLKBLD_I8253)	+= i8253.o
 obj-$(CONFIG_CLKSRC_MMIO)	+= mmio.o
+obj-$(CONFIG_DAVINCI_TIMER)	+= timer-davinci.o
 obj-$(CONFIG_DIGICOLOR_TIMER)	+= timer-digicolor.o
 obj-$(CONFIG_OMAP_DM_TIMER)	+= timer-ti-dm.o
 obj-$(CONFIG_DW_APB_TIMER)	+= dw_apb_timer.o

2.21.0

From: Bartosz Golaszewski <[email protected]>

Extend the davinci-timer driver to also register a clock source.

---
 drivers/clocksource/timer-davinci.c | 85 +++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

index 246a5564495d..62745c962049 100644
@@ -43,6 +43,8 @@
 #define DAVINCI_TIMER_MIN_DELTA			0x01
 #define DAVINCI_TIMER_MAX_DELTA			0xfffffffe
 
+#define DAVINCI_TIMER_CLKSRC_BITS		32
+
 #define DAVINCI_TIMER_TGCR_DEFAULT \
 		(DAVINCI_TIMER_TIMMODE_32BIT_UNCHAINED | DAVINCI_TIMER_UNRESET)
 

@@ -52,6 +54,16 @@ struct davinci_clockevent {
 	unsigned int cmp_off;
 };
 
+/*
+ * This must be globally accessible by davinci_timer_read_sched_clock(), so
+ * let's keep it here.
+ */
+static struct {
+	struct clocksource dev;
+	void __iomem *base;
+	unsigned int tim_off;
+} davinci_clocksource;
+
 static struct davinci_clockevent *
 to_davinci_clockevent(struct clock_event_device *clockevent)
 {

@@ -166,6 +178,53 @@ static irqreturn_t davinci_timer_irq_timer(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static u64 notrace davinci_timer_read_sched_clock(void)
+{
+	return readl_relaxed(davinci_clocksource.base +
+			     davinci_clocksource.tim_off);
+}
+
+static u64 davinci_clocksource_read(struct clocksource *dev)
+{
+	return davinci_timer_read_sched_clock();
+}
+
+/*
+ * Standard use-case: we're using tim12 for clockevent and tim34 for
+ * clocksource. The default is making the former run in oneshot mode
+ * and the latter in periodic mode.
+ */
+static void davinci_clocksource_init_tim34(void __iomem *base)
+{
+	int tcr;
+
+	tcr = DAVINCI_TIMER_ENAMODE_PERIODIC <<
+		DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
+	tcr |= DAVINCI_TIMER_ENAMODE_ONESHOT <<
+		DAVINCI_TIMER_ENAMODE_SHIFT_TIM12;
+
+	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM34);
+	writel_relaxed(UINT_MAX, base + DAVINCI_TIMER_REG_PRD34);
+	writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
+}
+
+/*
+ * Special use-case on da830: the DSP may use tim34. We're using tim12 for
+ * both clocksource and clockevent. We set tim12 to periodic and don't touch
+ * tim34.
+ */
+static void davinci_clocksource_init_tim12(void __iomem *base)
+{
+	unsigned int tcr;
+
+	tcr = DAVINCI_TIMER_ENAMODE_PERIODIC <<
+		DAVINCI_TIMER_ENAMODE_SHIFT_TIM12;
+
+	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM12);
+	writel_relaxed(UINT_MAX, base + DAVINCI_TIMER_REG_PRD12);
+	writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
+}
+
 static void davinci_timer_init(void __iomem *base)
 {
 	/* Set clock to internal mode and disable it. */

@@ -247,6 +306,32 @@ int __init davinci_timer_register(struct clk *clk,
 					DAVINCI_TIMER_MIN_DELTA,
 					DAVINCI_TIMER_MAX_DELTA);
 
+	davinci_clocksource.dev.rating = 300;
+	davinci_clocksource.dev.read = davinci_clocksource_read;
+	davinci_clocksource.dev.mask =
+			CLOCKSOURCE_MASK(DAVINCI_TIMER_CLKSRC_BITS);
+	davinci_clocksource.dev.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+	davinci_clocksource.base = base;
+
+	if (timer_cfg->cmp_off) {
+		davinci_clocksource.dev.name = "tim12";
+		davinci_clocksource.tim_off = DAVINCI_TIMER_REG_TIM12;
+		davinci_clocksource_init_tim12(base);
+	} else {
+		davinci_clocksource.dev.name = "tim34";
+		davinci_clocksource.tim_off = DAVINCI_TIMER_REG_TIM34;
+		davinci_clocksource_init_tim34(base);
+	}
+
+	rv = clocksource_register_hz(&davinci_clocksource.dev, tick_rate);
+	if (rv) {
+		pr_err("Unable to register clocksource");
+		return rv;
+	}
+
+	sched_clock_register(davinci_timer_read_sched_clock,
+			     DAVINCI_TIMER_CLKSRC_BITS, tick_rate);
+
 	return 0;
 }
 

2.21.0