soc: imx8mq: Read SOC revision from TF-A

SOC revision on older imx8mq is not available in fuses so on anything
other than B1 current code just reports "unknown".

TF-A already handles this by parsing the ROM and exposes the value
through a SMC call. Call this instead of reimplementing the workaround
in the kernel itself.
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/soc/imx/soc-imx8.c

@@ -9,6 +9,7 @@
 #include <linux/slab.h>
 #include <linux/sys_soc.h>
 #include <linux/platform_device.h>
+#include <linux/arm-smccc.h>
 #include <linux/of.h>
 
 #define REV_B1				0x21
@@ -16,6 +17,8 @@
 #define IMX8MQ_SW_INFO_B1		0x40
 #define IMX8MQ_SW_MAGIC_B1		0xff0055aa
 
+#define IMX_SIP_GET_SOC_INFO		0xc2000006
+
 #define OCOTP_UID_LOW			0x410
 #define OCOTP_UID_HIGH			0x420
 
@@ -29,6 +32,22 @@ struct imx8_soc_data {
 
 static u64 soc_uid;
 
+#ifdef CONFIG_HAVE_ARM_SMCCC
+static u32 imx8mq_soc_revision_from_atf(void)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(IMX_SIP_GET_SOC_INFO, 0, 0, 0, 0, 0, 0, 0, &res);
+
+	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
+		return 0;
+	else
+		return res.a0 & 0xff;
+}
+#else
+static inline u32 imx8mq_soc_revision_from_atf(void) { return 0; };
+#endif
+
 static u32 __init imx8mq_soc_revision(void)
 {
 	struct device_node *np;
@@ -43,9 +62,16 @@ static u32 __init imx8mq_soc_revision(void)
 	ocotp_base = of_iomap(np, 0);
 	WARN_ON(!ocotp_base);
 
-	magic = readl_relaxed(ocotp_base + IMX8MQ_SW_INFO_B1);
-	if (magic == IMX8MQ_SW_MAGIC_B1)
-		rev = REV_B1;
+	/*
+	 * SOC revision on older imx8mq is not available in fuses so query
+	 * the value from ATF instead.
+	 */
+	rev = imx8mq_soc_revision_from_atf();
+	if (!rev) {
+		magic = readl_relaxed(ocotp_base + IMX8MQ_SW_INFO_B1);
+		if (magic == IMX8MQ_SW_MAGIC_B1)
+			rev = REV_B1;
+	}
 
 	soc_uid = readl_relaxed(ocotp_base + OCOTP_UID_HIGH);
 	soc_uid <<= 32;