[RFC PATCH v2 2/3] cpufreq: sun50i: Add support for D1's speed bin decoding

[Brandon Cheo Fusi]

Adds support for decoding the efuse value read from D1 efuse speed
bins, and factors out equivalent code for sun50i.

The algorithm is gotten from

https://github.com/Tina-Linux/linux-5.4/blob/master/drivers/cpufreq/sun50i-cpufreq-nvmem.c#L293-L338

and maps an efuse value to either 0 or 1, with 1 meaning stable at
a lower supply voltage for the same clock frequency.

Signed-off-by: Brandon Cheo Fusi <fusibrandon13 at gmail.com>
---
 drivers/cpufreq/sun50i-cpufreq-nvmem.c | 34 ++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/cpufreq/sun50i-cpufreq-nvmem.c b/drivers/cpufreq/sun50i-cpufreq-nvmem.c
index fc509fc49..b1cb95308 100644
--- a/drivers/cpufreq/sun50i-cpufreq-nvmem.c
+++ b/drivers/cpufreq/sun50i-cpufreq-nvmem.c
@@ -29,6 +29,33 @@ struct sunxi_cpufreq_data {
 	u32 (*efuse_xlate)(u32 *speedbin, size_t len);
 };
 
+static u32 sun20i_efuse_xlate(u32 *speedbin, size_t len)
+{
+	u32 ret, efuse_value = 0;
+	int i;
+
+	for (i = 0; i < len; i++)
+		efuse_value |= ((u32)speedbin[i] << (i * 8));
+
+	switch (efuse_value) {
+	case 0x5e00:
+		/* QFN package */
+		ret = 0;
+		break;
+	case 0x5c00:
+	case 0x7400:
+		/* QFN package */
+		ret = 1;
+		break;
+	case 0x5000:
+	default:
+		/* BGA package */
+		ret = 0;
+	}
+
+	return ret;
+}
+
 static u32 sun50i_efuse_xlate(u32 *speedbin, size_t len)
 {
 	u32 efuse_value = 0;
@@ -46,6 +73,10 @@ static u32 sun50i_efuse_xlate(u32 *speedbin, size_t len)
 		return 0;
 }
 
+struct sunxi_cpufreq_data sun20i_cpufreq_data = {
+	.efuse_xlate = sun20i_efuse_xlate,
+};
+
 struct sunxi_cpufreq_data sun50i_cpufreq_data = {
 	.efuse_xlate = sun50i_efuse_xlate,
 };
@@ -54,6 +85,9 @@ static const struct of_device_id cpu_opp_match_list[] = {
 	{ .compatible = "allwinner,sun50i-h6-operating-points",
 	  .data = &sun50i_cpufreq_data,
 	},
+	{ .compatible = "allwinner,sun20i-d1-operating-points",
+	  .data = &sun20i_cpufreq_data,
+	},
 	{}
 };
 
-- 
2.30.2