[PATCH v2] soc: imx8mq: Read SOC revision from TF-A

[Leonard Crestez <leonard.crestez@nxp.com>]

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>

---
Changes since v1:
* Add ifdef to fix build on ARM older than v7 (kbuild robot)
Link to v1: https://patchwork.kernel.org/patch/11183813/

Alternatively a CONFIG_IMX8M_SOC config option could be created which
depends on HAVE_ARM_SMCCC but that also requires defconfig changes.

 drivers/soc/imx/soc-imx8.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/imx/soc-imx8.c b/drivers/soc/imx/soc-imx8.c
index fcbf745a9971..6a2916664438 100644
--- a/drivers/soc/imx/soc-imx8.c
+++ b/drivers/soc/imx/soc-imx8.c
@@ -7,17 +7,20 @@
 #include <linux/io.h>
 #include <linux/of_address.h>
 #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
 
 #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
 
 /* Same as ANADIG_DIGPROG_IMX7D */
 #define ANADIG_DIGPROG_IMX8MM	0x800
@@ -27,10 +30,26 @@ struct imx8_soc_data {
 	u32 (*soc_revision)(void);
 };
 
 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 u32 imx8mq_soc_revision_from_atf(void) { return 0; };
+#endif
+
 static u32 __init imx8mq_soc_revision(void)
 {
 	struct device_node *np;
 	void __iomem *ocotp_base;
 	u32 magic;
@@ -41,13 +60,20 @@ static u32 __init imx8mq_soc_revision(void)
 		goto out;
 
 	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;
 	soc_uid |= readl_relaxed(ocotp_base + OCOTP_UID_LOW);
 
-- 
2.17.1


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