[U-Boot] [PATCH] TI: DaVinci DA850 EVM: support passing device speed grade information to kernel

[Sekhar Nori]

The TI DA850/OMAP-L138/AM18x EVM can be populated with devices
of different speed grades.

The maximum speed the chip can support can only be determined from
the label on the package (not software readable).

Introduce a method to pass the speed grade information to kernel
using ATAG_REVISION. The kernel uses this information to determine
the maximum speed reachable using cpufreq.

Note that U-Boot itself does not set the CPU rate. The CPU
speed is setup by a primary bootloader ("UBL"). The rate setup
by UBL could be different from the maximum speed grade of the
device.

Signed-off-by: Sekhar Nori <nsekhar at ti.com>
---
Applies to latest of U-Boot mainline master 

 board/davinci/da8xxevm/da850evm.c |   38 +++++++++++++++++++++++++++++++++++++
 include/configs/da850evm.h        |    1 +
 2 files changed, 39 insertions(+), 0 deletions(-)

diff --git a/board/davinci/da8xxevm/da850evm.c b/board/davinci/da8xxevm/da850evm.c
index 959b2c6..6a6d4fb 100644
--- a/board/davinci/da8xxevm/da850evm.c
+++ b/board/davinci/da8xxevm/da850evm.c
@@ -70,6 +70,44 @@ static const struct lpsc_resource lpsc[] = {
 	{ DAVINCI_LPSC_GPIO },
 };
 
+#ifndef CONFIG_DA850_EVM_MAX_SPEED
+#define CONFIG_DA850_EVM_MAX_SPEED	300000
+#endif
+
+/*
+ * get_board_rev() - setup to pass kernel board revision information
+ * Returns:
+ * bit[0-3]	Maximum speed supported by the DA850/OMAP-L138/AM18x part
+ *		0 - 300 MHz
+ *		1 - 372 MHz
+ *		2 - 408 MHz
+ *		3 - 456 MHz
+ */
+u32 get_board_rev(void)
+{
+	char *s;
+	u32 maxspeed = CONFIG_DA850_EVM_MAX_SPEED;
+	u32 rev = 0;
+
+	s = getenv("maxspeed");
+	if (s)
+		maxspeed = simple_strtoul(s, NULL, 10);
+
+	switch (maxspeed) {
+	case 456000:
+		rev |= 3;
+		break;
+	case 408000:
+		rev |= 2;
+		break;
+	case 372000:
+		rev |= 1;
+		break;
+	}
+
+	return rev;
+}
+
 int board_init(void)
 {
 #ifndef CONFIG_USE_IRQ
diff --git a/include/configs/da850evm.h b/include/configs/da850evm.h
index 357715d..3ea9032 100644
--- a/include/configs/da850evm.h
+++ b/include/configs/da850evm.h
@@ -102,6 +102,7 @@
  */
 #define LINUX_BOOT_PARAM_ADDR	(CONFIG_SYS_MEMTEST_START + 0x100)
 #define CONFIG_CMDLINE_TAG
+#define CONFIG_REVISION_TAG
 #define CONFIG_SETUP_MEMORY_TAGS
 #define CONFIG_BOOTARGS		\
 	"mem=32M console=ttyS2,115200n8 root=/dev/mtdblock2 rw noinitrd ip=dhcp"
-- 
1.6.2.4