davinci: Support various speedgrades for MityDSP-L138 and MityARM-1808 SoMs

For the MityDSP-L138/MityARM-1808 SoMs, the speed grade can be determined
from the part number string read from the factory configuration block on
the on-board I2C PROM.  Configure the maximum CPU speed based on this
information.

This patch was tested using a MityDSP-L138 and MityARM-1808 at various
speedgrades.  Also, for code coverage, a bogus configuration was tested
as well as a configuration having an unknown part number.
Signed-off-by: Michael Williamson <michael.williamson@criticallink.com>
Tested-by: Michael Williamson <michael.williamson@criticallink.com>
Reviewed-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>

arch/arm/mach-davinci/board-mityomapl138.c

@@ -44,38 +44,109 @@ struct factory_config {
 
 static struct factory_config factory_config;
 
+struct part_no_info {
+	const char	*part_no;	/* part number string of interest */
+	int		max_freq;	/* khz */
+};
+
+static struct part_no_info mityomapl138_pn_info[] = {
+	{
+		.part_no	= "L138-C",
+		.max_freq	= 300000,
+	},
+	{
+		.part_no	= "L138-D",
+		.max_freq	= 375000,
+	},
+	{
+		.part_no	= "L138-F",
+		.max_freq	= 456000,
+	},
+	{
+		.part_no	= "1808-C",
+		.max_freq	= 300000,
+	},
+	{
+		.part_no	= "1808-D",
+		.max_freq	= 375000,
+	},
+	{
+		.part_no	= "1808-F",
+		.max_freq	= 456000,
+	},
+	{
+		.part_no	= "1810-D",
+		.max_freq	= 375000,
+	},
+};
+
+#ifdef CONFIG_CPU_FREQ
+static void mityomapl138_cpufreq_init(const char *partnum)
+{
+	int i, ret;
+
+	for (i = 0; partnum && i < ARRAY_SIZE(mityomapl138_pn_info); i++) {
+		/*
+		 * the part number has additional characters beyond what is
+		 * stored in the table.  This information is not needed for
+		 * determining the speed grade, and would require several
+		 * more table entries.  Only check the first N characters
+		 * for a match.
+		 */
+		if (!strncmp(partnum, mityomapl138_pn_info[i].part_no,
+			     strlen(mityomapl138_pn_info[i].part_no))) {
+			da850_max_speed = mityomapl138_pn_info[i].max_freq;
+			break;
+		}
+	}
+
+	ret = da850_register_cpufreq("pll0_sysclk3");
+	if (ret)
+		pr_warning("cpufreq registration failed: %d\n", ret);
+}
+#else
+static void mityomapl138_cpufreq_init(const char *partnum) { }
+#endif
+
 static void read_factory_config(struct memory_accessor *a, void *context)
 {
 	int ret;
+	const char *partnum = NULL;
 	struct davinci_soc_info *soc_info = &davinci_soc_info;
 
 	ret = a->read(a, (char *)&factory_config, 0, sizeof(factory_config));
 	if (ret != sizeof(struct factory_config)) {
 		pr_warning("MityOMAPL138: Read Factory Config Failed: %d\n",
 				ret);
-		return;
+		goto bad_config;
 	}
 
 	if (factory_config.magic != FACTORY_CONFIG_MAGIC) {
 		pr_warning("MityOMAPL138: Factory Config Magic Wrong (%X)\n",
 				factory_config.magic);
-		return;
+		goto bad_config;
 	}
 
 	if (factory_config.version != FACTORY_CONFIG_VERSION) {
 		pr_warning("MityOMAPL138: Factory Config Version Wrong (%X)\n",
 				factory_config.version);
-		return;
+		goto bad_config;
 	}
 
 	pr_info("MityOMAPL138: Found MAC = %pM\n", factory_config.mac);
-	pr_info("MityOMAPL138: Part Number = %s\n", factory_config.partnum);
 	if (is_valid_ether_addr(factory_config.mac))
 		memcpy(soc_info->emac_pdata->mac_addr,
 			factory_config.mac, ETH_ALEN);
 	else
 		pr_warning("MityOMAPL138: Invalid MAC found "
 				"in factory config block\n");
+
+	partnum = factory_config.partnum;
+	pr_info("MityOMAPL138: Part Number = %s\n", partnum);
+
+bad_config:
+	/* default maximum speed is valid for all platforms */
+	mityomapl138_cpufreq_init(partnum);
 }
 
 static struct at24_platform_data mityomapl138_fd_chip = {
@@ -383,10 +454,6 @@ static void __init mityomapl138_init(void)
 	if (ret)
 		pr_warning("rtc setup failed: %d\n", ret);
 
-	ret = da850_register_cpufreq("pll0_sysclk3");
-	if (ret)
-		pr_warning("cpufreq registration failed: %d\n", ret);
-
 	ret = da8xx_register_cpuidle();
 	if (ret)
 		pr_warning("cpuidle registration failed: %d\n", ret);