soc/intel/common/block/lpc: Add lpc_get_fixed_io_decode

Add function to return the fixed io decode ranges contained in register
0x80 of the LPC interface.

BUG=N/A
TEST=build

Change-Id: Ie46d7c9d7a399a8489c030d906f75ba61db19cc4
Signed-off-by: Wim Vervoorn <wvervoorn@eltan.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38745
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/common/block/include/intelblocks/lpc_lib.h

@@ -70,6 +70,8 @@ struct lpc_mmio_range {
  * Output:I/O Enable Bits
  */
 uint16_t lpc_enable_fixed_io_ranges(uint16_t io_enables);
+/* Return the current decode settings */
+uint16_t lpc_get_fixed_io_decode(void);
 /* Open a generic IO window to the LPC bus. Four windows are available. */
 void lpc_open_pmio_window(uint16_t base, uint16_t size);
 /* Close all generic IO windows to the LPC bus. */

src/soc/intel/common/block/lpc/lpc_lib.c

@@ -37,6 +37,11 @@ uint16_t lpc_enable_fixed_io_ranges(uint16_t io_enables)
 	return io_enables;
 }
 
+uint16_t lpc_get_fixed_io_decode(void)
+{
+	return pci_read_config16(PCH_DEV_LPC, LPC_IO_DECODE);
+}
+
 /*
  * Find the first unused IO window.
  * Returns -1 if not found, 0 for reg 0x84, 1 for reg 0x88 ...