OMAP2/3 GPTIMER: skip unnecessary TLDR write during non-autoreload

The GPTIMER TLDR register does not need to be written if the GPTIMER
is not in autoreload mode.  This is the usual case for dynamic tick-enabled
kernels.

Simulation data indicate that skipping the read that occurs as part of
the write should save at least 300-320 ns for each GPTIMER1 timer
reprogram.  (This assumes L4-Wakeup is at 19MHz and GPTIMER write
posting is enabled.)  Skipping the write itself probably won't have
much impact since it should be posted on the OCP interconnect.

Tested on 2430SDP and 3430SDP.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/arch/arm/plat-omap/dmtimer.c b/arch/arm/plat-omap/dmtimer.c
index 6111d99daccb30b5bca26a18f665a219587bfe3a..5708fd818e8c26cdf1fff942e96e95769627135d 100644 (file)
--- a/arch/arm/plat-omap/dmtimer.c
+++ b/arch/arm/plat-omap/dmtimer.c
@@ -549,14 +549,15 @@ void omap_dm_timer_set_load_start(struct omap_dm_timer *timer, int autoreload,
        u32 l;
 
        l = omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
-       if (autoreload)
+       if (autoreload) {
                l |= OMAP_TIMER_CTRL_AR;
-       else
+               omap_dm_timer_write_reg(timer, OMAP_TIMER_LOAD_REG, load);
+       } else {
                l &= ~OMAP_TIMER_CTRL_AR;
+       }
        l |= OMAP_TIMER_CTRL_ST;
 
        omap_dm_timer_write_reg(timer, OMAP_TIMER_COUNTER_REG, load);
-       omap_dm_timer_write_reg(timer, OMAP_TIMER_LOAD_REG, load);
        omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
 }