Re: [RFC PATCH v2 10/14] m68k: mac: Convert to clocksource API
On Tue, Nov 20, 2018 at 10:00 AM Finn Thain wrote: > If you use one timer as a clock event device and the other as a > clocksource, there are no timers left to run the existing > timer_interrupt() handler. So this arrangement would require > GENERIC_CLOCKEVENTS=y, right? I think so, yes. > Then, wouldn't all relevant platforms have to support > GENERIC_CLOCKEVENTS=y, if a single binary was to support all of those > platforms? Good point. I wonder of there is a path forward where we could have peaceful GENERIC_CLOCKEVENTS and !GENERIC_CLOCKEVENTS co-existence. Yours, Linus Walleij
Re: [RFC PATCH v2 10/14] m68k: mac: Convert to clocksource API
On Tue, 20 Nov 2018, Linus Walleij wrote: > On Mon, Nov 19, 2018 at 2:22 AM Finn Thain wrote: > > > Add a platform clocksource by adapting the existing arch_gettimeoffset > > implementation. > > > > Signed-off-by: Finn Thain > > Acked-by: Linus Walleij > > Tested-by: Stan Johnson > > As noted for the Amiga CIA (which is pretty much a sibling to this MOS > 6522 VIA) this chip also has two counters and could use one as > clocksource and the other as clock event. > > Again I bet this is just using one timer out of habit. > > It will be an easy feat to make a clean clocksource+clock event for this > hardware as well once this refactoring is complete. > Right. Both timer 1 and timer 2 have a timed interrupt mode, and either could probably serve as a clock event device or a clocksource. Some Mac models have a second VIA with two more timers, but not all. (As clock event devices, the longest interval you can program is about 83 ms. As 783360 Hz, 16-bit clocksources, they wrap about 12 times every second.) If you use one timer as a clock event device and the other as a clocksource, there are no timers left to run the existing timer_interrupt() handler. So this arrangement would require GENERIC_CLOCKEVENTS=y, right? Then, wouldn't all relevant platforms have to support GENERIC_CLOCKEVENTS=y, if a single binary was to support all of those platforms? -- > Yours, > Linus Walleij >
Re: [RFC PATCH v2 10/14] m68k: mac: Convert to clocksource API
On Mon, Nov 19, 2018 at 2:22 AM Finn Thain wrote: > Add a platform clocksource by adapting the existing arch_gettimeoffset > implementation. > > Signed-off-by: Finn Thain > Acked-by: Linus Walleij > Tested-by: Stan Johnson As noted for the Amiga CIA (which is pretty much a sibling to this MOS 6522 VIA) this chip also has two counters and could use one as clocksource and the other as clock event. Again I bet this is just using one timer out of habit. It will be an easy feat to make a clean clocksource+clock event for this hardware as well once this refactoring is complete. Yours, Linus Walleij
[RFC PATCH v2 10/14] m68k: mac: Convert to clocksource API
Add a platform clocksource by adapting the existing arch_gettimeoffset
implementation.
Signed-off-by: Finn Thain
Acked-by: Linus Walleij
Tested-by: Stan Johnson
---
Changed since v1:
- Moved clk_total access to within the irq lock.
- Use type u32 for tick counter.
---
arch/m68k/mac/via.c | 46 -
1 file changed, 37 insertions(+), 9 deletions(-)
diff --git a/arch/m68k/mac/via.c b/arch/m68k/mac/via.c
index d1dbf9017300..de59a5cb4250 100644
--- a/arch/m68k/mac/via.c
+++ b/arch/m68k/mac/via.c
@@ -23,6 +23,7 @@
*
*/
+#include
#include
#include
#include
@@ -573,16 +574,40 @@ EXPORT_SYMBOL(via2_scsi_drq_pending);
/* timer and clock source */
#define VIA_CLOCK_FREQ 783360/* VIA "phase 2" clock in Hz
*/
-#define VIA_TIMER_INTERVAL (100 / HZ)/* microseconds per jiffy */
#define VIA_TIMER_CYCLES (VIA_CLOCK_FREQ / HZ) /* clock cycles per jiffy */
#define VIA_TC (VIA_TIMER_CYCLES - 2) /* including 0 and -1 */
#define VIA_TC_LOW (VIA_TC & 0xFF)
#define VIA_TC_HIGH(VIA_TC >> 8)
+static u64 mac_read_clk(struct clocksource *cs);
+
+static struct clocksource mac_clk = {
+ .name = "via1",
+ .rating = 250,
+ .read = mac_read_clk,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static u32 clk_total;
+static u32 clk_offset;
+
+static irqreturn_t via_timer_handler(int irq, void *dev_id)
+{
+ irq_handler_t timer_routine = dev_id;
+
+ clk_total += VIA_TIMER_CYCLES;
+ clk_offset = 0;
+ timer_routine(0, NULL);
+
+ return IRQ_HANDLED;
+}
+
void __init via_init_clock(irq_handler_t timer_routine)
{
- if (request_irq(IRQ_MAC_TIMER_1, timer_routine, 0, "timer", NULL)) {
+ if (request_irq(IRQ_MAC_TIMER_1, via_timer_handler, IRQF_TIMER, "timer",
+ timer_routine)) {
pr_err("Couldn't register %s interrupt\n", "timer");
return;
}
@@ -592,13 +617,16 @@ void __init via_init_clock(irq_handler_t timer_routine)
via1[vT1CL] = VIA_TC_LOW;
via1[vT1CH] = VIA_TC_HIGH;
via1[vACR] |= 0x40;
+
+ clocksource_register_hz(_clk, VIA_CLOCK_FREQ);
}
-u32 mac_gettimeoffset(void)
+static u64 mac_read_clk(struct clocksource *cs)
{
unsigned long flags;
u8 count_high;
- u16 count, offset = 0;
+ u16 count;
+ u32 ticks;
/*
* Timer counter wrap-around is detected with the timer interrupt flag
@@ -617,11 +645,11 @@ u32 mac_gettimeoffset(void)
/* spin */;
}
if (via1[vIFR] & VIA_TIMER_1_INT)
- offset = VIA_TIMER_CYCLES;
- local_irq_restore(flags);
-
+ clk_offset = VIA_TIMER_CYCLES;
count = count_high << 8;
- count = VIA_TIMER_CYCLES - count + offset;
+ ticks = VIA_TIMER_CYCLES - count;
+ ticks += clk_offset + clk_total;
+ local_irq_restore(flags);
- return ((count * VIA_TIMER_INTERVAL) / VIA_TIMER_CYCLES) * 1000;
+ return ticks;
}
--
2.18.1
