cpufreq: ti-cpufreq: Introduce quirks to handle syscon fails appropriately

Commit b4bc9f9e ("cpufreq: ti-cpufreq: add support for omap34xx
and omap36xx") introduced special handling for OMAP3 class devices
where syscon node may not be present. However, this also creates a bug
where the syscon node is present, however the offset used to read
is beyond the syscon defined range.

Fix this by providing a quirk option that is populated when such
special handling is required. This allows proper failure for all other
platforms when the syscon node and efuse offsets are mismatched.

Fixes: b4bc9f9e ("cpufreq: ti-cpufreq: add support for omap34xx and omap36xx")
Signed-off-by: Nishanth Menon <nm@ti.com>
Tested-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/ti-cpufreq.c

@@ -90,6 +90,9 @@ struct ti_cpufreq_soc_data {
 	unsigned long efuse_shift;
 	unsigned long rev_offset;
 	bool multi_regulator;
+/* Backward compatibility hack: Might have missing syscon */
+#define TI_QUIRK_SYSCON_MAY_BE_MISSING	0x1
+	u8 quirks;
 };
 
 struct ti_cpufreq_data {
@@ -254,6 +257,7 @@ static struct ti_cpufreq_soc_data omap34xx_soc_data = {
 	.efuse_mask = BIT(3),
 	.rev_offset = OMAP3_CONTROL_IDCODE - OMAP3_SYSCON_BASE,
 	.multi_regulator = false,
+	.quirks = TI_QUIRK_SYSCON_MAY_BE_MISSING,
 };
 
 /*
@@ -281,6 +285,7 @@ static struct ti_cpufreq_soc_data omap36xx_soc_data = {
 	.efuse_mask = BIT(9),
 	.rev_offset = OMAP3_CONTROL_IDCODE - OMAP3_SYSCON_BASE,
 	.multi_regulator = true,
+	.quirks = TI_QUIRK_SYSCON_MAY_BE_MISSING,
 };
 
 /*
@@ -295,6 +300,7 @@ static struct ti_cpufreq_soc_data am3517_soc_data = {
 	.efuse_mask = 0,
 	.rev_offset = OMAP3_CONTROL_IDCODE - OMAP3_SYSCON_BASE,
 	.multi_regulator = false,
+	.quirks = TI_QUIRK_SYSCON_MAY_BE_MISSING,
 };
 
 static struct ti_cpufreq_soc_data am625_soc_data = {
@@ -340,7 +346,7 @@ static int ti_cpufreq_get_efuse(struct ti_cpufreq_data *opp_data,
 
 	ret = regmap_read(opp_data->syscon, opp_data->soc_data->efuse_offset,
 			  &efuse);
-	if (ret == -EIO) {
+	if (opp_data->soc_data->quirks & TI_QUIRK_SYSCON_MAY_BE_MISSING && ret == -EIO) {
 		/* not a syscon register! */
 		void __iomem *regs = ioremap(OMAP3_SYSCON_BASE +
 				opp_data->soc_data->efuse_offset, 4);
@@ -381,7 +387,7 @@ static int ti_cpufreq_get_rev(struct ti_cpufreq_data *opp_data,
 
 	ret = regmap_read(opp_data->syscon, opp_data->soc_data->rev_offset,
 			  &revision);
-	if (ret == -EIO) {
+	if (opp_data->soc_data->quirks & TI_QUIRK_SYSCON_MAY_BE_MISSING && ret == -EIO) {
 		/* not a syscon register! */
 		void __iomem *regs = ioremap(OMAP3_SYSCON_BASE +
 				opp_data->soc_data->rev_offset, 4);