CHROMIUM: memconsole: Add ACPI method to locate cbmem start

[cascardo/linux.git] / drivers / firmware / google / memconsole.c

diff --git a/drivers/firmware/google/memconsole.c b/drivers/firmware/google/memconsole.c
index 6e17ac9..acedda5 100644 (file)
--- a/drivers/firmware/google/memconsole.c
+++ b/drivers/firmware/google/memconsole.c
@@ -18,6 +18,7 @@
 #include <linux/mm.h>
 #include <asm/bios_ebda.h>
 #include <asm/e820.h>
+#include <acpi/acpi_bus.h>
 
 #define BIOS_MEMCONSOLE_V1_MAGIC       0xDEADBABE
 #define BIOS_MEMCONSOLE_V2_MAGIC       (('M')|('C'<<8)|('O'<<16)|('N'<<24))
@@ -119,25 +120,44 @@ struct cbmem_cons {
 
 struct cbmem_cons __iomem *cbmem_console;
 
-static bool check_cbmem(void)
-{
-       struct sysinfo sysi;
-       phys_addr_t top_of_ram, scan_addr;
-
-       /* coreboot CBMEM constants */
+/* coreboot CBMEM constants */
 #define CBMEM_ALIGNMENT   (128 * 1024)
 #define MEMORY_BOUNDARY   (1024 * 1024 * 1024)
 #define MAX_CBMEM_ENTRIES 16
 #define CBMEM_ENTRY_MAGIC 0x434f5245
 #define CBMEM_CONSOLE_ID  0x434f4e53
+#define CBMEM_ACPI_NAME   "\\CMEM"
+
+static bool check_cbmem(void)
+{
+       struct sysinfo sysi;
+       phys_addr_t top_of_ram, scan_addr = 0;
+       acpi_handle handle;
+       acpi_status status;
+       unsigned long long value;
 
        /*
-        * Determine where to start looking for CBMEM signature: take the top
-        * of usable memory and align it up to 128K boundary.
+        * Attempt to use defined ACPI name to locate CBMEM TOC.
         */
-       si_meminfo(&sysi);
-       top_of_ram = (phys_addr_t) sysi.totalram << PAGE_SHIFT;
-       scan_addr = ALIGN(top_of_ram, CBMEM_ALIGNMENT) + CBMEM_ALIGNMENT;
+       status = acpi_get_handle(NULL, CBMEM_ACPI_NAME, &handle);
+       if (ACPI_SUCCESS(status)) {
+               status = acpi_evaluate_integer(handle, CBMEM_ACPI_NAME,
+                                              NULL, &value);
+               /* Start scan at this address */
+               if (ACPI_SUCCESS(status) && value > 0)
+                       scan_addr = (phys_addr_t) value;
+       }
+
+       /*
+        * Otherwise determine where to start looking for CBMEM signature:
+        * take the top of usable memory and align it up to 128K boundary.
+        */
+       if (!scan_addr) {
+               si_meminfo(&sysi);
+               top_of_ram = (phys_addr_t) sysi.totalram << PAGE_SHIFT;
+               scan_addr = ALIGN(top_of_ram, CBMEM_ALIGNMENT) +
+                       CBMEM_ALIGNMENT;
+       }
 
        while (scan_addr % MEMORY_BOUNDARY) {
                struct cbmem_entry __iomem *pcbm;
@@ -154,6 +174,11 @@ static bool check_cbmem(void)
                        break;
 
                pcbm = ioremap(scan_addr, remap_size);
+               if (!pcbm) {
+                       scan_addr += CBMEM_ALIGNMENT;
+                       continue;
+               }
+
                if (pcbm->magic != CBMEM_ENTRY_MAGIC) {
                        iounmap(pcbm);
                        scan_addr += CBMEM_ALIGNMENT;