[PATCH v2 1/1] drivers: rng: add support for Meson S4

[Alexey Romanov]

For some Amlogic SOC's, mechanism to obtain random number
has been changed. For example, S4 now uses status bit waiting algo.

Signed-off-by: Alexey Romanov <avroma...@salutedevices.com>
---
 drivers/rng/meson-rng.c | 72 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/drivers/rng/meson-rng.c b/drivers/rng/meson-rng.c
index e0a1e8c7e0..ba60325b94 100644
--- a/drivers/rng/meson-rng.c
+++ b/drivers/rng/meson-rng.c
@@ -10,10 +10,23 @@
 #include <dm.h>
 #include <rng.h>
 #include <asm/io.h>
+#include <linux/iopoll.h>
+
+#define RNG_DATA       0x00
+#define RNG_S4_DATA    0x08
+#define RNG_S4_CFG     0x00
+
+#define RUN_BIT                BIT(0)
+#define SEED_READY_STS_BIT     BIT(31)
+
+struct meson_rng_priv {
+       u32 (*read)(fdt_addr_t base);
+};
 
 struct meson_rng_plat {
        fdt_addr_t base;
        struct clk clk;
+       struct meson_rng_priv *priv;
 };
 
 /**
@@ -27,10 +40,11 @@ struct meson_rng_plat {
 static int meson_rng_read(struct udevice *dev, void *data, size_t len)
 {
        struct meson_rng_plat *pdata = dev_get_plat(dev);
+       struct meson_rng_priv *priv = pdata->priv;
        char *buffer = (char *)data;
 
        while (len) {
-               u32 rand = readl(pdata->base);
+               u32 rand = priv->read(pdata->base);
                size_t step;
 
                if (len >= 4)
@@ -44,6 +58,47 @@ static int meson_rng_read(struct udevice *dev, void *data, 
size_t len)
        return 0;
 }
 
+static int meson_rng_wait_status(void __iomem *cfg_addr, int bit)
+{
+       u32 status = 0;
+       int ret;
+
+       ret = readl_relaxed_poll_timeout(cfg_addr,
+                                        status, !(status & bit),
+                                        10000);
+       if (ret)
+               return -EBUSY;
+
+       return 0;
+}
+
+static u32 meson_common_rng_read(fdt_addr_t base)
+{
+       return readl(base);
+}
+
+static u32 meson_s4_rng_read(fdt_addr_t base)
+{
+       void __iomem *cfg_addr = (void *)base + RNG_S4_CFG;
+       int err;
+
+       writel_relaxed(readl_relaxed(cfg_addr) | SEED_READY_STS_BIT, cfg_addr);
+
+       err = meson_rng_wait_status(cfg_addr, SEED_READY_STS_BIT);
+       if (err) {
+               pr_err("Seed isn't ready, try again\n");
+               return err;
+       }
+
+       err = meson_rng_wait_status(cfg_addr, RUN_BIT);
+       if (err) {
+               pr_err("Can't get random number, try again\n");
+               return err;
+       }
+
+       return readl_relaxed(base + RNG_S4_DATA);
+}
+
 /**
  * meson_rng_probe() - probe rng device
  *
@@ -59,6 +114,8 @@ static int meson_rng_probe(struct udevice *dev)
        if (err)
                return err;
 
+       pdata->priv = dev_get_driver_data(dev);
+
        return 0;
 }
 
@@ -102,9 +159,22 @@ static const struct dm_rng_ops meson_rng_ops = {
        .read = meson_rng_read,
 };
 
+static const struct meson_rng_priv meson_rng_priv = {
+       .read = meson_common_rng_read,
+};
+
+static const struct meson_rng_priv meson_rng_priv_s4 = {
+       .read = meson_s4_rng_read,
+};
+
 static const struct udevice_id meson_rng_match[] = {
        {
                .compatible = "amlogic,meson-rng",
+               .data = (ulong)&meson_rng_priv,
+       },
+       {
+               .compatible = "amlogic,meson-s4-rng",
+               .data = (ulong)&meson_rng_priv_s4,
        },
        {},
 };
-- 
2.25.1