ACPI: Add CMOS RTC Operation Region handler support

On HP Folio 13-2000, the BIOS defines a CMOS RTC Operation Region and
the EC's _REG methord accesses that region.  Thus an appropriate
address space handler must be registered for that region before the
EC driver is loaded.

Introduce a mechanism for adding CMOS RTC address space handlers.
Register an ACPI scan handler for CMOS RTC devices such that, when
a device of that kind is detected during an ACPI namespace scan, a
common CMOS RTC operation region address space handler will be
installed for it.

References: https://bugzilla.kernel.org/show_bug.cgi?id=54621
Reported-and-tested-by: Stefan Nagy <public@stefan-nagy.at>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Cc: 3.9+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 92 insertions, 0 deletions

diff --git a/drivers/acpi/acpi_cmos_rtc.c b/drivers/acpi/acpi_cmos_rtc.c
new file mode 100644
index 000000000000..84190ed89c04
--- /dev/null
+++ b/drivers/acpi/acpi_cmos_rtc.c
@@ -0,0 +1,92 @@
+/*
+ * ACPI support for CMOS RTC Address Space access
+ *
+ * Copyright (C) 2013, Intel Corporation
+ * Authors: Lan Tianyu <tianyu.lan@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <asm-generic/rtc.h>
+
+#include "internal.h"
+
+#define PREFIX "ACPI: "
+
+ACPI_MODULE_NAME("cmos rtc");
+
+static const struct acpi_device_id acpi_cmos_rtc_ids[] = {
+        { "PNP0B00" },
+        { "PNP0B01" },
+        { "PNP0B02" },
+        {}
+};
+
+static acpi_status
+acpi_cmos_rtc_space_handler(u32 function, acpi_physical_address address,
+                      u32 bits, u64 *value64,
+                      void *handler_context, void *region_context)
+{
+        int i;
+        u8 *value = (u8 *)&value64;
+
+        if (address > 0xff || !value64)
+                return AE_BAD_PARAMETER;
+
+        if (function != ACPI_WRITE && function != ACPI_READ)
+                return AE_BAD_PARAMETER;
+
+        spin_lock_irq(&rtc_lock);
+
+        for (i = 0; i < DIV_ROUND_UP(bits, 8); ++i, ++address, ++value)
+                if (function == ACPI_READ)
+                        *value = CMOS_READ(address);
+                else
+                        CMOS_WRITE(*value, address);
+
+        spin_unlock_irq(&rtc_lock);
+
+        return AE_OK;
+}
+
+static int acpi_install_cmos_rtc_space_handler(struct acpi_device *adev,
+                const struct acpi_device_id *id)
+{
+        acpi_status status;
+
+        status = acpi_install_address_space_handler(adev->handle,
+                        ACPI_ADR_SPACE_CMOS,
+                        &acpi_cmos_rtc_space_handler,
+                        NULL, NULL);
+        if (ACPI_FAILURE(status)) {
+                pr_err(PREFIX "Error installing CMOS-RTC region handler\n");
+                return -ENODEV;
+        }
+
+        return 0;
+}
+
+static void acpi_remove_cmos_rtc_space_handler(struct acpi_device *adev)
+{
+        if (ACPI_FAILURE(acpi_remove_address_space_handler(adev->handle,
+                        ACPI_ADR_SPACE_CMOS, &acpi_cmos_rtc_space_handler)))
+                pr_err(PREFIX "Error removing CMOS-RTC region handler\n");
+}
+
+static struct acpi_scan_handler cmos_rtc_handler = {
+        .ids = acpi_cmos_rtc_ids,
+        .attach = acpi_install_cmos_rtc_space_handler,
+        .detach = acpi_remove_cmos_rtc_space_handler,
+};
+
+void __init acpi_cmos_rtc_init(void)
+{
+        acpi_scan_add_handler(&cmos_rtc_handler);
+}