Since we don't want to create the Lynxpoint LPSS clock tree on a machines
where no LPSS exists at all we look for the Lynxpoint device ACPI HIDs
during ACPI namespace scan and if a known device is seen we assume that it
is safe to create the LPSS clocks.

Therefore we allow init function to be passed via acpi_platform_device_ids[]
table which is called whenever the corresponding device is found.

Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
---
 drivers/acpi/scan.c |   36 +++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 6a12702..8d9965e 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -11,6 +11,7 @@
 #include <linux/kthread.h>
 #include <linux/dmi.h>
 #include <linux/nls.h>
+#include <linux/platform_device.h>
 
 #include <acpi/acpi_drivers.h>
 
@@ -29,6 +30,15 @@ extern struct acpi_device *acpi_root;
 
 static const char *dummy_hid = "device";
 
+static void lpt_lpss_init_once(void)
+{
+       static struct platform_device *pdev;
+
+       /* Lynxpoint LPSS clocks */
+       if (!pdev)
+               pdev = platform_device_register_simple("clk-lpt", -1, NULL, 0);
+}
+
 /*
  * The following ACPI IDs are known to be suitable for representing as
  * platform devices.
@@ -38,14 +48,14 @@ static const struct acpi_device_id 
acpi_platform_device_ids[] = {
        { "PNP0D40" },
 
        /* Haswell LPSS devices */
-       { "INT33C0", 0 },
-       { "INT33C1", 0 },
-       { "INT33C2", 0 },
-       { "INT33C3", 0 },
-       { "INT33C4", 0 },
-       { "INT33C5", 0 },
-       { "INT33C6", 0 },
-       { "INT33C7", 0 },
+       { "INT33C0", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C1", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C2", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C3", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C4", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C5", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C6", (kernel_ulong_t)lpt_lpss_init_once },
+       { "INT33C7", (kernel_ulong_t)lpt_lpss_init_once },
 
        { }
 };
@@ -1580,6 +1590,7 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, 
u32 lvl_not_used,
 static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
                                          void *not_used, void **ret_not_used)
 {
+       const struct acpi_device_id *id;
        acpi_status status = AE_OK;
        struct acpi_device *device;
        unsigned long long sta_not_used;
@@ -1595,7 +1606,14 @@ static acpi_status acpi_bus_device_attach(acpi_handle 
handle, u32 lvl_not_used,
        if (acpi_bus_get_device(handle, &device))
                return AE_CTRL_DEPTH;
 
-       if (!acpi_match_device_ids(device, acpi_platform_device_ids)) {
+       id = __acpi_match_device(device, acpi_platform_device_ids);
+       if (id) {
+               void (*init)(void) = (void (*)(void))id->driver_data;
+
+               /* Run any initialization if required */
+               if (init)
+                       init();
+
                /* This is a known good platform device. */
                acpi_create_platform_device(device);
        } else if (device_attach(&device->dev) < 0) {
-- 
1.7.10.4

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