astbmc: Enable mbox depending on scratch reg

[ Upstream commit b09e48f ]

P8 boxes can opt in for mbox pnor support if they set the scratch
register bit to indicate it is supported.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

hw/ast-bmc/ast-io.c

@@ -116,6 +116,7 @@
  */
 
 #define BMC_SIO_SCR29 0x29
+#define BMC_SIO_SCR29_MBOX 0x08
 #define BMC_SIO_SCR29_MEMBOOT 0x10
 
 enum {
@@ -427,6 +428,19 @@ bool ast_is_ahb_lpc_pnor(void)
 	return !(boot_flags & BMC_SIO_SCR29_MEMBOOT);
 }
 
+bool ast_scratch_reg_is_mbox(void)
+{
+	uint8_t boot_version;
+	uint8_t boot_flags;
+
+	boot_version = bmc_sio_inb(BMC_SIO_SCR28);
+	if (boot_version != BOOT_FLAGS_VERSION)
+		return false;
+
+	boot_flags = bmc_sio_inb(BMC_SIO_SCR29);
+	return boot_flags & BMC_SIO_SCR29_MBOX;
+}
+
 void ast_setup_ibt(uint16_t io_base, uint8_t irq)
 {
 	uint32_t v;

include/ast.h

@@ -82,6 +82,7 @@ int ast_copy_from_ahb(void *dst, uint32_t reg, uint32_t len);
 void ast_io_init(void);
 bool ast_is_ahb_lpc_pnor(void);
 bool ast_is_mbox_pnor(void);
+bool ast_scratch_reg_is_mbox(void);
 
 /* UART configuration */
 

platforms/astbmc/common.c

@@ -213,8 +213,9 @@ static void astbmc_fixup_dt_mbox(struct dt_node *lpc)
 	struct dt_node *mbox;
 	char namebuf[32];
 
-	/* All P9 machines have this and no earlier machines do */
-	if (proc_gen != proc_gen_p9)
+	/* All P9 machines use mbox. P8 machines can indicate they support
+	 * it using the scratch register */
+	if (proc_gen != proc_gen_p9 && !ast_scratch_reg_is_mbox())
 		return;
 
 	/* First check if the mbox interface is already there */