Tony Lindgren [off-list ref] writes:

This patch makes timer-gp.c to use only a subset of dmtimer
functions without the need to initialize dmtimer code early.

Also note that now with the inline functions, timer_set_next_event
becomes more efficient in the lines of assembly code.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Kevin Hilman <redacted>

In order for this to work, *all* the dmtimer functions need to be
converted.  Some still call the real driver, which may not yet be
initialized (as pointed out for [7/10]...

[...]

+static int __init omap_dm_timer_init_one(struct omap_dm_timer *timer,
+						int gptimer_id,
+						const char *fck_source)
 {
-	u32 tick_rate;
-	int src;
-	char clockevent_hwmod_name[8]; /* 8 = sizeof("timerXX0") */
+	char name[10]; /* 10 = sizeof("gptXX_Xck0") */
+	struct omap_hwmod *oh;
+	size_t size;
+	int res = 0;
+
+	sprintf(name, "timer%d", gptimer_id);
+	omap_hwmod_setup_one(name);
+	oh = omap_hwmod_lookup(name);
+	if (!oh)
+		return -ENODEV;
+
+	timer->irq = oh->mpu_irqs[0].irq;
+	timer->phys_base = oh->slaves[0]->addr->pa_start;
+	size = oh->slaves[0]->addr->pa_end - timer->phys_base;
+
+	/* Static mapping, never released */
+	timer->io_base = ioremap(timer->phys_base, size);
+	if (!timer->io_base)
+		return -ENXIO;
+
+	/* After the dmtimer is using hwmod these clocks won't be needed */
+	sprintf(name, "gpt%d_fck", gptimer_id);
+	timer->fclk = clk_get(NULL, name);
+	if (IS_ERR(timer->fclk))
+		return -ENODEV;
+
+	sprintf(name, "gpt%d_ick", gptimer_id);
+	timer->iclk = clk_get(NULL, name);
+	if (IS_ERR(timer->iclk)) {
+		clk_put(timer->fclk);
+		return -ENODEV;
+	}
 
-	inited = 1;
+	omap_hwmod_enable(oh);
+
+	if (gptimer_id != 12) {
+		struct clk *src;
+
+		src = clk_get(NULL, fck_source);
+		if (IS_ERR(src)) {
+			res = -EINVAL;
+		} else {
+			res = __omap_dm_timer_set_source(timer->fclk, src);
+			if (IS_ERR_VALUE(res))
+				pr_warning("%s: timer%i cannot set source\n",
+						__func__, gptimer_id);
+			clk_put(src);
+		}
+	}
+	__omap_dm_timer_reset(timer->io_base, 1, 1);
+	timer->posted = 1;
+
+	timer->rate = clk_get_rate(timer->fclk);
 
-	sprintf(clockevent_hwmod_name, "timer%d", gptimer_id);
-	omap_hwmod_setup_one(clockevent_hwmod_name);
+	timer->reserved = 1;
 
 	gptimer = omap_dm_timer_request_specific(gptimer_id);

Here remains a call to the real driver, which is not yet initialized
when called from sys_timer.init.

 	BUG_ON(gptimer == NULL);
 	gptimer_wakeup = gptimer;
 
-#if defined(CONFIG_OMAP_32K_TIMER)
-	src = OMAP_TIMER_SRC_32_KHZ;
-#else
-	src = OMAP_TIMER_SRC_SYS_CLK;
-	WARN(gptimer_id == 12, "WARNING: GPTIMER12 can only use the "
-	     "secure 32KiHz clock source\n");
-#endif
+	return res;
+}

Kevin