ARM: at91: fix at91_sysirq_mask_rtc for sam9x5 SoCs

sam9x5 SoCs have the following errata:
 "RTC: Interrupt Mask Register cannot be used
  Interrupt Mask Register read always returns 0."

Hence we should not rely on what IMR claims about already masked IRQs
and just disable all IRQs.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Reported-by: Bryan Evenson <bevenson@melinkcorp.com>
Reviewed-by: Johan Hovold <johan@hovold.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Bryan Evenson <bevenson@melinkcorp.com>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Mark Roszko <mark.roszko@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/mach-at91/sysirq_mask.c b/arch/arm/mach-at91/sysirq_mask.c
index 2ba694f9626b69f348b96d71db3450656a859361..f8bc3511a8c8b49c82084a21593e74ffbfa6ccd6 100644 (file)
--- a/arch/arm/mach-at91/sysirq_mask.c
+++ b/arch/arm/mach-at91/sysirq_mask.c
@@ -25,24 +25,28 @@
 
 #include "generic.h"
 
-#define AT91_RTC_IDR   0x24    /* Interrupt Disable Register */
-#define AT91_RTC_IMR   0x28    /* Interrupt Mask Register */
+#define AT91_RTC_IDR           0x24    /* Interrupt Disable Register */
+#define AT91_RTC_IMR           0x28    /* Interrupt Mask Register */
+#define AT91_RTC_IRQ_MASK      0x1f    /* Available IRQs mask */
 
 void __init at91_sysirq_mask_rtc(u32 rtc_base)
 {
        void __iomem *base;
-       u32 mask;
 
        base = ioremap(rtc_base, 64);
        if (!base)
                return;
 
-       mask = readl_relaxed(base + AT91_RTC_IMR);
-       if (mask) {
-               pr_info("AT91: Disabling rtc irq\n");
-               writel_relaxed(mask, base + AT91_RTC_IDR);
-               (void)readl_relaxed(base + AT91_RTC_IMR);       /* flush */
-       }
+       /*
+        * sam9x5 SoCs have the following errata:
+        * "RTC: Interrupt Mask Register cannot be used
+        *  Interrupt Mask Register read always returns 0."
+        *
+        * Hence we're not relying on IMR values to disable
+        * interrupts.
+        */
+       writel_relaxed(AT91_RTC_IRQ_MASK, base + AT91_RTC_IDR);
+       (void)readl_relaxed(base + AT91_RTC_IMR);       /* flush */
 
        iounmap(base);
 }