Le 14/01/2022 à 11:46, Arnd Bergmann a écrit :
On Thu, Jan 13, 2022 at 9:19 PM Laurent Vivier <laurent@xxxxxxxxx> wrote:
Add a clocksource based on the goldfish-rtc device.
Signed-off-by: Laurent Vivier <laurent@xxxxxxxxx>
---
drivers/clocksource/Kconfig | 7 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-goldfish.c | 130 +++++++++++++++++++++++++++
include/clocksource/timer-goldfish.h | 12 +++
4 files changed, 150 insertions(+)
create mode 100644 drivers/clocksource/timer-goldfish.c
create mode 100644 include/clocksource/timer-goldfish.h
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index f65e31bab9ae..6ca9bb78407d 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -711,4 +711,11 @@ config MICROCHIP_PIT64B
modes and high resolution. It is used as a clocksource
and a clockevent.
+config GOLDFISH_TIMER
+ bool "Clocksource using goldfish-rtc"
+ select RTC_CLASS
+ select RTC_DRV_GOLDFISH
This should probably be
depends on M68K || COMPILE_TEST
depends on RTC_DRV_GOLDFISH
A driver should never 'select' another user-selectable subsystem
ok
+static int goldfish_timer_set_oneshot(struct clock_event_device *evt)
+{
+ struct goldfish_timer *timerdrv = ced_to_gf(evt);
+ void __iomem *base = timerdrv->base;
+
+ __raw_writel(0, base + TIMER_ALARM_HIGH);
+ __raw_writel(0, base + TIMER_ALARM_LOW);
+ __raw_writel(1, base + TIMER_IRQ_ENABLED);
As mentioned elsewhere, the __raw_* accessors are not portable, please
use readl()/writel() here, or possibly ioread32_be()/iowrite32_be() for
the big-endian variant.
We can't use readl()/writel() here because it's supposed to read from a little endian device, and
goldfish endianness depends on the endianness of the machine.
For goldfish, readl()/writel() works fine on little-endian machine but not on big-endian machine.
On m68k, you have:
#define readl(addr) in_le32(addr)
#define writel(val,addr) out_le32((addr),(val))
and with goldfish it's wrong as the device is not little-endian, it is big-endian like the machine.
same comment with ioread32_be()/iowrite32_be(): it will work on big-endian machine not on little-endian.
We need an accessor that doesn't byteswap the value, that accesses it natively, and in all other
parts of the kernel __raw_writel() and __raw_readl() are used.
Thanks,
Laurent
