drivers: hwinfo: Add LiteX DNA driver

This commit adds driver supporting reading DNA ID value for LiteX SoC
builder.

Signed-off-by: Jakub Wegnerowski <jwegnerowski@internships.antmicro.com>
Signed-off-by: Mateusz Holenko <mholenko@antmicro.com>

drivers/hwinfo/CMakeLists.txt

@@ -10,5 +10,5 @@ zephyr_sources_ifdef(CONFIG_HWINFO_ESP32      hwinfo_esp32.c)
 zephyr_sources_ifdef(CONFIG_HWINFO_IMXRT      hwinfo_imxrt.c)
 zephyr_sources_ifdef(CONFIG_HWINFO_SAM        hwinfo_sam.c)
 zephyr_sources_ifdef(CONFIG_HWINFO_SAM0       hwinfo_sam0.c)
-
+zephyr_sources_ifdef(CONFIG_HWINFO_LITEX      hwinfo_litex.c)
 zephyr_sources_ifdef(CONFIG_HWINFO_SHELL hwinfo_shell.c)

drivers/hwinfo/Kconfig

@@ -69,4 +69,10 @@ config HWINFO_ESP32
 	help
 	  Enable ESP32 hwinfo driver.
 
+config HWINFO_LITEX
+	bool "LiteX device ID"
+	default y
+	depends on SOC_RISCV32_LITEX_VEXRISCV
+	help
+	  Enable LiteX hwinfo driver
 endif

drivers/hwinfo/hwinfo_litex.c

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2019 Antmicro <www.antmicro.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <drivers/hwinfo.h>
+#include <soc.h>
+#include <string.h>
+#include <device.h>
+#include <sys/util.h>
+
+ssize_t z_impl_hwinfo_get_device_id(u8_t *buffer, size_t length)
+{
+	u32_t volatile *ptr = (u32_t volatile *)(DT_INST_0_LITEX_DNA0_BASE_ADDRESS);
+	ssize_t end = MIN(length, (DT_INST_0_LITEX_DNA0_SIZE / sizeof(u32_t)));
+
+	for (int i = 0; i < end; i++) {
+		/* In LiteX even though registers are 32-bit wide, each one
+		   contains meaningful data only in the lowest 8 bits */
+		buffer[i] = (u8_t)(ptr[i] & 0xff);
+	}
+
+	return end;
+}

dts/bindings/hwinfo/litex,dna0.yaml

@@ -0,0 +1,20 @@
+#
+# Copyright (c)  2019 Antmicro <www.antmicro.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+title: LiteX DNA
+description: >
+    This binding gives a base representation of the LiteX DNA
+inherits:
+        !include base.yaml
+
+properties:
+    compatible:
+      constraint: "litex,dna0"
+
+    reg:
+      category: required
+
+