rtc: sun6i: Add NVMEM provider

The sun6i RTC provides 32 bytes of general-purpose data registers.
They can be used to save data in the always-on RTC power domain.
The registers are writable via 32-bit MMIO accesses only.

Expose them with a NVMEM provider so they can be used by other drivers.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220413231731.56709-1-samuel@sholland.org

diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
index 5b3e4da..755aeb8 100644 (file)
--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c
@@ -71,6 +71,10 @@
 #define SUN6I_LOSC_OUT_GATING                  0x0060
 #define SUN6I_LOSC_OUT_GATING_EN_OFFSET                0
 
+/* General-purpose data */
+#define SUN6I_GP_DATA                          0x0100
+#define SUN6I_GP_DATA_SIZE                     0x20
+
 /*
  * Get date values
  */
@@ -662,6 +666,39 @@ static const struct rtc_class_ops sun6i_rtc_ops = {
        .alarm_irq_enable       = sun6i_rtc_alarm_irq_enable
 };
 
+static int sun6i_rtc_nvmem_read(void *priv, unsigned int offset, void *_val, size_t bytes)
+{
+       struct sun6i_rtc_dev *chip = priv;
+       u32 *val = _val;
+       int i;
+
+       for (i = 0; i < bytes / 4; ++i)
+               val[i] = readl(chip->base + SUN6I_GP_DATA + offset + 4 * i);
+
+       return 0;
+}
+
+static int sun6i_rtc_nvmem_write(void *priv, unsigned int offset, void *_val, size_t bytes)
+{
+       struct sun6i_rtc_dev *chip = priv;
+       u32 *val = _val;
+       int i;
+
+       for (i = 0; i < bytes / 4; ++i)
+               writel(val[i], chip->base + SUN6I_GP_DATA + offset + 4 * i);
+
+       return 0;
+}
+
+static struct nvmem_config sun6i_rtc_nvmem_cfg = {
+       .type           = NVMEM_TYPE_BATTERY_BACKED,
+       .reg_read       = sun6i_rtc_nvmem_read,
+       .reg_write      = sun6i_rtc_nvmem_write,
+       .size           = SUN6I_GP_DATA_SIZE,
+       .word_size      = 4,
+       .stride         = 4,
+};
+
 #ifdef CONFIG_PM_SLEEP
 /* Enable IRQ wake on suspend, to wake up from RTC. */
 static int sun6i_rtc_suspend(struct device *dev)
@@ -795,6 +832,11 @@ static int sun6i_rtc_probe(struct platform_device *pdev)
        if (ret)
                return ret;
 
+       sun6i_rtc_nvmem_cfg.priv = chip;
+       ret = devm_rtc_nvmem_register(chip->rtc, &sun6i_rtc_nvmem_cfg);
+       if (ret)
+               return ret;
+
        dev_info(&pdev->dev, "RTC enabled\n");
 
        return 0;