[PATCH v2 3/8] hwrng: omap - Switch to non-obsolete read API implementation

[Romain Perier <romain.perier@free-electrons.com>]

The ".data_present" and ".data_read" operations are marked as
OBSOLETE in the hwrng API. We have to use the ".read" operation instead.
It makes the driver simpler and removes the need to do a busy loop to
wait until enough data is generated by the IP. We simplify this step by
only checking the status of the engine, if there is data, we copy the
data to the output buffer and the amout of copied data is returned to the
caller, otherwise zero is returned. The hwrng core will re-call the read
operation as many times as required until enough data has been copied.

Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
---
 drivers/char/hw_random/omap-rng.c | 39 ++++++++++++---------------------------
 1 file changed, 12 insertions(+), 27 deletions(-)

diff --git a/drivers/char/hw_random/omap-rng.c b/drivers/char/hw_random/omap-rng.c
index 01d4be2..d47b24d 100644
--- a/drivers/char/hw_random/omap-rng.c
+++ b/drivers/char/hw_random/omap-rng.c
@@ -140,41 +140,27 @@ static inline void omap_rng_write(struct omap_rng_dev *priv, u16 reg,
 	__raw_writel(val, priv->base + priv->pdata->regs[reg]);
 }
 
-static int omap_rng_data_present(struct hwrng *rng, int wait)
+
+static int omap_rng_do_read(struct hwrng *rng, void *data, size_t max,
+			    bool wait)
 {
 	struct omap_rng_dev *priv;
-	int data, i;
 
 	priv = (struct omap_rng_dev *)rng->priv;
 
-	for (i = 0; i < 20; i++) {
-		data = priv->pdata->data_present(priv);
-		if (data || !wait)
-			break;
-		/* RNG produces data fast enough (2+ MBit/sec, even
-		 * during "rngtest" loads, that these delays don't
-		 * seem to trigger.  We *could* use the RNG IRQ, but
-		 * that'd be higher overhead ... so why bother?
-		 */
-		udelay(10);
-	}
-	return data;
-}
-
-static int omap_rng_data_read(struct hwrng *rng, u32 *data)
-{
-	struct omap_rng_dev *priv;
-	u32 data_size, i;
+	if (max < priv->pdata->data_size)
+		return 0;
 
-	priv = (struct omap_rng_dev *)rng->priv;
-	data_size = priv->pdata->data_size;
+	if (!priv->pdata->data_present(priv))
+		return 0;
 
-	for (i = 0; i < data_size / sizeof(u32); i++)
-		data[i] = omap_rng_read(priv, RNG_OUTPUT_L_REG + i);
+	memcpy_fromio(data, priv->base + priv->pdata->regs[RNG_OUTPUT_L_REG],
+		      priv->pdata->data_size);
 
 	if (priv->pdata->regs[RNG_INTACK_REG])
 		omap_rng_write(priv, RNG_INTACK_REG, RNG_REG_INTACK_RDY_MASK);
-	return data_size;
+
+	return priv->pdata->data_size;
 }
 
 static int omap_rng_init(struct hwrng *rng)
@@ -195,8 +181,7 @@ static void omap_rng_cleanup(struct hwrng *rng)
 
 static struct hwrng omap_rng_ops = {
 	.name		= "omap",
-	.data_present	= omap_rng_data_present,
-	.data_read	= omap_rng_data_read,
+	.read 		= omap_rng_do_read,
 	.init		= omap_rng_init,
 	.cleanup	= omap_rng_cleanup,
 };
-- 
2.9.3