nvmem: mtk-efuse: remove nvmem regmap dependency

Regmap raw accessors are bus specific implementations, using regmap raw
apis in nvmem breaks nvmem providers based on regmap mmio.
This patch moves to nvmem support in the driver to use callback
instead of regmap, which is what the nvmem core supports now.
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/Kconfig

@@ -50,7 +50,6 @@ config MTK_EFUSE
 	tristate "Mediatek SoCs EFUSE support"
 	depends on ARCH_MEDIATEK || COMPILE_TEST
 	depends on HAS_IOMEM
-	select REGMAP_MMIO
 	help
 	  This is a driver to access hardware related data like sensor
 	  calibration, HDMI impedance etc.

drivers/nvmem/mtk-efuse.c

@@ -14,15 +14,35 @@
 
 #include <linux/device.h>
 #include <linux/module.h>
+#include <linux/io.h>
 #include <linux/nvmem-provider.h>
 #include <linux/platform_device.h>
-#include <linux/regmap.h>
 
-static struct regmap_config mtk_regmap_config = {
-	.reg_bits = 32,
-	.val_bits = 32,
-	.reg_stride = 4,
-};
+static int mtk_reg_read(void *context,
+			unsigned int reg, void *_val, size_t bytes)
+{
+	void __iomem *base = context;
+	u32 *val = _val;
+	int i = 0, words = bytes / 4;
+
+	while (words--)
+		*val++ = readl(base + reg + (i++ * 4));
+
+	return 0;
+}
+
+static int mtk_reg_write(void *context,
+			 unsigned int reg, void *_val, size_t bytes)
+{
+	void __iomem *base = context;
+	u32 *val = _val;
+	int i = 0, words = bytes / 4;
+
+	while (words--)
+		writel(*val++, base + reg + (i++ * 4));
+
+	return 0;
+}
 
 static int mtk_efuse_probe(struct platform_device *pdev)
 {
@@ -30,7 +50,6 @@ static int mtk_efuse_probe(struct platform_device *pdev)
 	struct resource *res;
 	struct nvmem_device *nvmem;
 	struct nvmem_config *econfig;
-	struct regmap *regmap;
 	void __iomem *base;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -42,14 +61,12 @@ static int mtk_efuse_probe(struct platform_device *pdev)
 	if (!econfig)
 		return -ENOMEM;
 
-	mtk_regmap_config.max_register = resource_size(res) - 1;
-
-	regmap = devm_regmap_init_mmio(dev, base, &mtk_regmap_config);
-	if (IS_ERR(regmap)) {
-		dev_err(dev, "regmap init failed\n");
-		return PTR_ERR(regmap);
-	}
-
+	econfig->stride = 4;
+	econfig->word_size = 4;
+	econfig->reg_read = mtk_reg_read;
+	econfig->reg_write = mtk_reg_write;
+	econfig->size = resource_size(res);
+	econfig->priv = base;
 	econfig->dev = dev;
 	econfig->owner = THIS_MODULE;
 	nvmem = nvmem_register(econfig);