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Groups > linux.kernel > #1294904
| From | Daniel Lezcano <daniel.lezcano@linaro.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 36/69] clocksource/drivers/dw_apb_timer_of: Implement ARM delay timer |
| Date | 2015-12-18 15:40 +0100 |
| Message-ID | <qH4mn-6QB-51@gated-at.bofh.it> (permalink) |
| References | <qGIcb-Ma-41@gated-at.bofh.it> <qH42Z-6Hj-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: Jisheng Zhang <jszhang@marvell.com>
Implement an ARM delay timer to be used for udelay(). This allows us to
skip the delay loop calibration at boot on Marvell BG2, BG2Q, BG2CD
platforms. And after this patch, udelay() will be unaffected by CPU
frequency changes.
Note: Although in case there are several possible delay timers, we may
not select the "best" delay timer. Take one Marvell Berlin platform for
example: we have arch timer and dw-apb timer. The arch timer freq is
25MHZ while the dw-apb timer freq is 100MHZ, current selection would
choose the dw-apb timer. But the dw apb timer is on the APB bus while
arch timer sits in CPU, the cost of accessing the apb timer is higher
than the arch timer. We could introduce "rating" concept to delay
timer, but this approach "brings a lot of complexity and workarounds
in the code for a small benefit" as pointed out by Daniel.
Later, Arnd pointed out "However, we could argue that this actually
doesn't matter at all, because the entire point of the ndelay()/
udelay()/mdelay() functions is to waste CPU cycles doing not much at
all, so we can just as well waste them reading the timer register
than spinning on the CPU reading the arch timer more often.", so we
just simply register the dw apb base delay timer.
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
drivers/clocksource/dw_apb_timer_of.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
index a19a3f6..860843c 100644
--- a/drivers/clocksource/dw_apb_timer_of.c
+++ b/drivers/clocksource/dw_apb_timer_of.c
@@ -16,6 +16,7 @@
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <linux/delay.h>
#include <linux/dw_apb_timer.h>
#include <linux/of.h>
#include <linux/of_address.h>
@@ -130,6 +131,17 @@ static void __init init_sched_clock(void)
sched_clock_register(read_sched_clock, 32, sched_rate);
}
+#ifdef CONFIG_ARM
+static unsigned long dw_apb_delay_timer_read(void)
+{
+ return ~readl_relaxed(sched_io_base);
+}
+
+static struct delay_timer dw_apb_delay_timer = {
+ .read_current_timer = dw_apb_delay_timer_read,
+};
+#endif
+
static int num_called;
static void __init dw_apb_timer_init(struct device_node *timer)
{
@@ -142,6 +154,10 @@ static void __init dw_apb_timer_init(struct device_node *timer)
pr_debug("%s: found clocksource timer\n", __func__);
add_clocksource(timer);
init_sched_clock();
+#ifdef CONFIG_ARM
+ dw_apb_delay_timer.freq = sched_rate;
+ register_current_timer_delay(&dw_apb_delay_timer);
+#endif
break;
default:
break;
--
1.9.1
--
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[GIT PULL] clockevents for 4.5 Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-17 16:00 +0100
[PATCH 59/69] clocksource/drivers/dw_apb_timer: Use {readl|writel}_relaxed in critical path Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 11/69] clocksource/drivers/pxa_timer: Move the Kconfig rule Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 31/69] clocksource/drivers/prcmu: Fix Kconfig and add COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 03/69] clocksource/drivers/mtk_timer: Fix memleak in mtk_timer_init() Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 41/69] clocksource/drivers/h8300_timer8: Remove unused headers Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 05/69] clocksource/drivers/rockchip: Make the driver more readable Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 01/69] clocksource/drivers/mtk_timer: Add pr_fmt define Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 21/69] clocksource/drivers/dw_apb: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 07/69] clocksource/drivers/rockchip: Remove dsb() usage Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 34/69] clocksource/drivers/fsl-ftm: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 25/69] clocksource/drivers/vt8500: Remove unneeded header Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 53/69] clocksource/drivers/timer_sun5i: Replace code by clocksource_mmio_init Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:20 +0100
[PATCH 49/69] clocksource/drivers/h8300_timer16: Remove unused macros Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 54/69] clocksource/drivers/h8300_timer8: Separate the Kconfig option from the arch Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 51/69] clocksource/drivers/h8300_timer16: Fix irq return value check Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 66/69] clocksource/drivers/h8300: Fix timer not overflow case Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 47/69] clocksource/drivers/h8300_timer8: Retrieve the clock rate at init time Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 60/69] clocksource/drivers/dw_apb_timer: Inline apbt_readl and apbt_writel Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 65/69] clocksource/drivers/h8300: Change to overflow interrupt Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 55/69] h8300: Rename ctlr_out/in[bwl] to raw_read/write[bwl] Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 52/69] clocksource/drivers/h8300_timer16: Remove pointless lock Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 64/69] clocksource/drivers/lpc32: Correct pr_err() output format Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 48/69] clocksource/drivers/h8300_timer16: Remove pointless headers Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 63/69] clocksource/drivers/arm_global_timer: Fix suspend resume Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 68/69] clocksource/drivers/h8300: Initializer cleanup. Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 56/69] clocksource/drivers/h8300: Increase the compilation test coverage Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 67/69] clocksource/drivers/h8300: Simplify delta handling Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 50/69] clocksource/drivers/h8300_timer16: Remove unused fields in timer16_priv Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 44/69] clocksource/drivers/h8300_timer8: Fix irq return value check Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 58/69] clocksource/drivers/dw_apb_timer: Fix apbt_readl return types Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 45/69] clocksource/drivers/h8300_timer8: Remove pointless irq re-entrant safe code Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 62/69] clocksource/drivers/pistachio: Fix wrong calculated clocksource read value Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 46/69] clocksource/drivers/h8300_timer8: Remove irq and lock legacy code Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 69/69] clocksource/drivers/h8300: Use ioread / iowrite Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 61/69] clockevents/drivers/arm_global_timer: Use writel_relaxed in gt_compare_set Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 57/69] clocksource/drivers/tango-xtal: Replace code by clocksource_mmio_init Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:30 +0100
[PATCH 43/69] clocksource/drivers/h8300_timer8: Remove PERIODIC and ONESHOT macro Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 20/69] clocksource/drivers/digicolor: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 19/69] clocksource/drivers/orion: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 37/69] clocksource/drivers/h8300: Cleanup startup and remove module code. Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 30/69] clocksource/drivers/nomadik_mtu: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 40/69] clocksource/drivers/h8300_tpu: Remove pointless headers for TPU Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 39/69] clocksource/drivers/h8300_tpu: Remove unused macros Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 35/69] clocksource/drivers/Kconfig: Add missing GENERIC_CLOCKEVENTS dependency Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 27/69] clocksource/drivers/cadence_ttc: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 13/69] clocksource/drivers/tango: Add COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 17/69] clocksource/drivers/armada-370-xp: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 38/69] clocksource/drivers/h8300_timer8: Fix compilation error with dev_warn Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 42/69] clocksource/drivers/h8300_timer8: Remove unused macros Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 36/69] clocksource/drivers/dw_apb_timer_of: Implement ARM delay timer Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 26/69] clocksource/drivers/vt8500: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 22/69] clocksource/drivers/sun4i: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 12/69] clocksource/drivers/pxa_timer: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 23/69] clocksource/drivers/sun5i: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 28/69] clocksource/drivers/asm9260: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 18/69] clocksource/drivers/meson6: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 32/69] clocksource/drivers/exynos_mct: Fix Kconfig and add COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 24/69] clocksource/drivers/tegra2: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 29/69] clocksource/drivers/lpc32xx: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 33/69] clocksource/drivers/samsung-pwm: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:40 +0100
[PATCH 14/69] clocksource/drivers/pistachio: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
[PATCH 08/69] clocksource/drivers/qcom: Make COMPILE_TEST enabled for ARM architecture Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
[PATCH 09/69] clocksource/drivers/st_lpc: Fix Kconfig dependency Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
[PATCH 02/69] clocksource/drivers/mtk_timer: Fix pr_warn() messages in mtk_timer_init Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
Re: [PATCH 02/69] clocksource/drivers/mtk_timer: Fix pr_warn() messages in mtk_timer_init Matthias Brugger <matthias.bgg@gmail.com> - 2015-12-30 19:20 +0100
[PATCH 15/69] clocksource/drivers/mediatek: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
Re: [PATCH 15/69] clocksource/drivers/mediatek: Add the COMPILE_TEST option Matthias Brugger <matthias.bgg@gmail.com> - 2015-12-30 19:20 +0100
[PATCH 10/69] clocksource/drivers/st_lpc: Add the COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
[PATCH 06/69] time: Define dummy functions for the generic sched clock Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
[PATCH 16/69] clocksource/drivers/rockchip: Add COMPILE_TEST option Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
[PATCH 04/69] clocksource/drivers/tegra: Allow timer irq affinity change Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-12-18 15:50 +0100
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