Tegra410 and Tegra241 deprecate the HIDREV register. The recommended
method is to use Arm SMCCC to retrieve the chip ID, major and minor
revisions, and platform information.

Prefer Arm SMCCC when the platform supports it; fall back to HIDREV
otherwise. Behavior on older Tegra SoCs that do not support Arm SMCCC
remains unchanged.

Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
---
Changes in v2:
 - Fix HIDREV read during driver probe. Move it to tegra_read_chipid(),
   which is called on platforms that do not support SMCCC SoC calls.
---
 drivers/soc/tegra/fuse/tegra-apbmisc.c | 40 +++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/drivers/soc/tegra/fuse/tegra-apbmisc.c b/drivers/soc/tegra/fuse/tegra-apbmisc.c
index 0ce94fdc536f..87ae63a7e52d 100644
--- a/drivers/soc/tegra/fuse/tegra-apbmisc.c
+++ b/drivers/soc/tegra/fuse/tegra-apbmisc.c
@@ -4,6 +4,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/arm-smccc.h>
 #include <linux/export.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -27,6 +28,11 @@
 #define PMC_STRAPPING_OPT_A_RAM_CODE_MASK_SHORT	\
 	(0x3 << PMC_STRAPPING_OPT_A_RAM_CODE_SHIFT)
 
+#define TEGRA_SMCCC_PLATFORM(x)		(((x) >> 8) & 0xff)
+#define TEGRA_SMCCC_CHIP_ID(x)		(((x) >> 4) & 0xff)
+#define TEGRA_SMCCC_MAJOR_REV(x)	((x) & 0xf)
+#define TEGRA_SMCCC_MINOR_REV(x)	((x) & 0xf)
+
 static void __iomem *apbmisc_base;
 static bool long_ram_code;
 static u32 strapping;
@@ -34,28 +40,56 @@ static u32 chipid;
 
 u32 tegra_read_chipid(void)
 {
-	WARN(!chipid, "Tegra APB MISC not yet available\n");
+	WARN(!apbmisc_base, "Tegra APB MISC not yet available\n");
+
+	if (!chipid)
+		chipid = readl_relaxed(apbmisc_base + 4);
 
 	return chipid;
 }
 
 u8 tegra_get_chip_id(void)
 {
+#if IS_ENABLED(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)
+	s32 soc_id = arm_smccc_get_soc_id_version();
+
+	if (soc_id >= 0)
+		return TEGRA_SMCCC_CHIP_ID(soc_id);
+#endif
 	return (tegra_read_chipid() >> 8) & 0xff;
 }
 
 u8 tegra_get_major_rev(void)
 {
+#if IS_ENABLED(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)
+	s32 soc_id = arm_smccc_get_soc_id_version();
+
+	if (soc_id >= 0)
+		return TEGRA_SMCCC_MAJOR_REV(soc_id);
+#endif
 	return (tegra_read_chipid() >> 4) & 0xf;
 }
 
 u8 tegra_get_minor_rev(void)
 {
+#if IS_ENABLED(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)
+	s32 revision = arm_smccc_get_soc_id_revision();
+
+	if (revision >= 0)
+		return TEGRA_SMCCC_MINOR_REV(revision);
+#endif
 	return (tegra_read_chipid() >> 16) & 0xf;
+
 }
 
 u8 tegra_get_platform(void)
 {
+#if IS_ENABLED(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)
+	s32 revision = arm_smccc_get_soc_id_revision();
+
+	if (revision >= 0)
+		return TEGRA_SMCCC_PLATFORM(revision);
+#endif
 	return (tegra_read_chipid() >> 20) & 0xf;
 }
 
@@ -170,9 +204,7 @@ static void tegra_init_apbmisc_resources(struct resource *apbmisc,
 	void __iomem *strapping_base;
 
 	apbmisc_base = ioremap(apbmisc->start, resource_size(apbmisc));
-	if (apbmisc_base)
-		chipid = readl_relaxed(apbmisc_base + 4);
-	else
+	if (!apbmisc_base)
 		pr_err("failed to map APBMISC registers\n");
 
 	strapping_base = ioremap(straps->start, resource_size(straps));
-- 
2.43.0

From: Thierry Reding <treding@nvidia.com>


On Thu, 14 May 2026 11:00:41 +0530, Kartik Rajput wrote:
> Tegra410 and Tegra241 deprecate the HIDREV register. The recommended
> method is to use Arm SMCCC to retrieve the chip ID, major and minor
> revisions, and platform information.
> 
> Prefer Arm SMCCC when the platform supports it; fall back to HIDREV
> otherwise. Behavior on older Tegra SoCs that do not support Arm SMCCC
> remains unchanged.
> 
> [...]

Applied, thanks!

[1/1] soc/tegra: Use Arm SMCCC to get chip ID, revision, and platform info
      commit: d79fed917b35bb689d82457200f95e1939e5811e

Best regards,
-- 
Thierry Reding <treding@nvidia.com>