From e9f08bbe3f97829975d2b59091ef557101c83f61 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Wed, 12 Jun 2013 14:04:56 -0700 Subject: [PATCH] rtc-at91rm9200: add shadow interrupt mask Add shadow interrupt-mask register which can be used on SoCs where the actual hardware register is broken. Note that some care needs to be taken to make sure the shadow mask corresponds to the actual hardware state. The added overhead is not an issue for the non-broken SoCs due to the relatively infrequent interrupt-mask updates. We do, however, only use the shadow mask value as a fall-back when it actually needed as there is still a theoretical possibility that the mask is incorrect (see the code for details). Signed-off-by: Johan Hovold Acked-by: Nicolas Ferre Cc: Douglas Gilbert Cc: Jean-Christophe PLAGNIOL-VILLARD Cc: Ludovic Desroches Cc: Robert Nelson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/rtc/rtc-at91rm9200.c | 39 +++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c index 9592d08f3b11..811a102092d4 100644 --- a/drivers/rtc/rtc-at91rm9200.c +++ b/drivers/rtc/rtc-at91rm9200.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include #include @@ -43,6 +44,7 @@ #define AT91_RTC_EPOCH 1900UL /* just like arch/arm/common/rtctime.c */ struct at91_rtc_config { + bool use_shadow_imr; }; static const struct at91_rtc_config *at91_rtc_config; @@ -50,20 +52,55 @@ static DECLARE_COMPLETION(at91_rtc_updated); static unsigned int at91_alarm_year = AT91_RTC_EPOCH; static void __iomem *at91_rtc_regs; static int irq; +static DEFINE_SPINLOCK(at91_rtc_lock); +static u32 at91_rtc_shadow_imr; static void at91_rtc_write_ier(u32 mask) { + unsigned long flags; + + spin_lock_irqsave(&at91_rtc_lock, flags); + at91_rtc_shadow_imr |= mask; at91_rtc_write(AT91_RTC_IER, mask); + spin_unlock_irqrestore(&at91_rtc_lock, flags); } static void at91_rtc_write_idr(u32 mask) { + unsigned long flags; + + spin_lock_irqsave(&at91_rtc_lock, flags); at91_rtc_write(AT91_RTC_IDR, mask); + /* + * Register read back (of any RTC-register) needed to make sure + * IDR-register write has reached the peripheral before updating + * shadow mask. + * + * Note that there is still a possibility that the mask is updated + * before interrupts have actually been disabled in hardware. The only + * way to be certain would be to poll the IMR-register, which is is + * the very register we are trying to emulate. The register read back + * is a reasonable heuristic. + */ + at91_rtc_read(AT91_RTC_SR); + at91_rtc_shadow_imr &= ~mask; + spin_unlock_irqrestore(&at91_rtc_lock, flags); } static u32 at91_rtc_read_imr(void) { - return at91_rtc_read(AT91_RTC_IMR); + unsigned long flags; + u32 mask; + + if (at91_rtc_config->use_shadow_imr) { + spin_lock_irqsave(&at91_rtc_lock, flags); + mask = at91_rtc_shadow_imr; + spin_unlock_irqrestore(&at91_rtc_lock, flags); + } else { + mask = at91_rtc_read(AT91_RTC_IMR); + } + + return mask; } /* -- 2.20.1