Hi Lee
Late but...
On 17/09/15 14:45, Lee Jones wrote:
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 055bb01..8bcfb45 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -30,4 +30,5 @@ obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
+obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
diff --git a/drivers/char/hw_random/st-rng.c b/drivers/char/hw_random/st-rng.c
new file mode 100644
index 0000000..8c8a435
--- /dev/null
+++ b/drivers/char/hw_random/st-rng.c
@@ -0,0 +1,144 @@
+/*
+ * ST Random Number Generator Driver ST's Platforms
+ *
+ * Author: Pankaj Dev: <pankaj.dev@xxxxxx>
+ * Lee Jones <lee.jones@xxxxxxxxxx>
+ *
+ * Copyright (C) 2015 STMicroelectronics (R&D) Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/* Registers */
+#define ST_RNG_STATUS_REG 0x20
+#define ST_RNG_DATA_REG 0x24
+
+/* Registers fields */
+#define ST_RNG_STATUS_BAD_SEQUENCE BIT(0)
+#define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)
+#define ST_RNG_STATUS_FIFO_FULL BIT(5)
+
+#define ST_RNG_FIFO_SIZE 8
+#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
+
+/* Samples are available every 0.667us, which we round to 1us */
+#define ST_RNG_FILL_FIFO_TIMEOUT (1 * (ST_RNG_FIFO_SIZE / ST_RNG_SAMPLE_SIZE))
+
+struct st_rng_data {
+ void __iomem *base;
+ struct clk *clk;
+ struct hwrng ops;
+};
+
+static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+ struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
+ u32 status;
+ int i;
+
+ if (max < sizeof(u16))
+ return -EINVAL;
+
+ /* Wait until FIFO is full - max 4uS*/
+ for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
+ status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
+ if (status & ST_RNG_STATUS_FIFO_FULL)
+ break;
+ udelay(1);
How much bandwidth does using udelay() cost? I think it could be >10%
compared to a tighter polling loop.
+ }
+
+ if (i == ST_RNG_FILL_FIFO_TIMEOUT)
+ return 0;
Isn't a timeout an error condition?
+
+ for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
+ *(u16 *)(data + i) =
+ readl_relaxed(ddata->base + ST_RNG_DATA_REG);
+
+ return i; /* No of bytes read */
+}
+
+static int st_rng_probe(struct platform_device *pdev)
+{
+ struct st_rng_data *ddata;
+ struct resource *res;
+ struct clk *clk;
+ void __iomem *base;
+ int ret;
+
+ ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
+ if (!ddata)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ base = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(base))
+ return PTR_ERR(base);
+
+ clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+
+ ret = clk_prepare_enable(clk);
+ if (ret)
+ return ret;
+
+ ddata->ops.priv = (unsigned long)ddata;
+ ddata->ops.read = st_rng_read;
+ ddata->ops.name = pdev->name;
+ ddata->base = base;
+ ddata->clk = clk;
+
+ dev_set_drvdata(&pdev->dev, ddata);
+
+ ret = hwrng_register(&ddata->ops);
+ if (ret) {
+ dev_err(&pdev->dev, "Failed to register HW RNG\n");
Why shout about this particular error but not any others? Perhaps just
rely on the driver core to report the error here?
+ return ret;
+ }
+
+ dev_info(&pdev->dev, "Successfully registered HW RNG\n");
+
+ return 0;
+}
+
+static int st_rng_remove(struct platform_device *pdev)
+{
+ struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
+
+ hwrng_unregister(&ddata->ops);
+
+ clk_disable_unprepare(ddata->clk);
This mismatches the error paths in the probe function (there is no
cleanup of clock counts in probe function).
Daniel.
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