hwrng: imx-rngc - simpler check for available random bytes

The "level" field in the status register contains the number of random
bytes that are available in the FIFO.  Use GENMASK to extract this field.
We only want to check if level is 0 or if we can read another byte.
There's no need for the shift or the level variable.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c
index a1c2414..cf29c32 100644 (file)
--- a/drivers/char/hw_random/imx-rngc.c
+++ b/drivers/char/hw_random/imx-rngc.c
@@ -17,6 +17,7 @@
 #include <linux/hw_random.h>
 #include <linux/completion.h>
 #include <linux/io.h>
+#include <linux/bitfield.h>
 
 #define RNGC_VER_ID                    0x0000
 #define RNGC_COMMAND                   0x0004
@@ -44,8 +45,7 @@
 #define RNGC_CTRL_AUTO_SEED            0x00000010
 
 #define RNGC_STATUS_ERROR              0x00010000
-#define RNGC_STATUS_FIFO_LEVEL_MASK    0x00000f00
-#define RNGC_STATUS_FIFO_LEVEL_SHIFT   8
+#define RNGC_STATUS_FIFO_LEVEL_MASK    GENMASK(11, 8)
 #define RNGC_STATUS_SEED_DONE          0x00000020
 #define RNGC_STATUS_ST_DONE            0x00000010
 
@@ -122,7 +122,6 @@ static int imx_rngc_read(struct hwrng *rng, void *data, size_t max, bool wait)
 {
        struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
        unsigned int status;
-       unsigned int level;
        int retval = 0;
 
        while (max >= sizeof(u32)) {
@@ -132,11 +131,7 @@ static int imx_rngc_read(struct hwrng *rng, void *data, size_t max, bool wait)
                if (status & RNGC_STATUS_ERROR)
                        break;
 
-               /* how many random numbers are in FIFO? [0-16] */
-               level = (status & RNGC_STATUS_FIFO_LEVEL_MASK) >>
-                       RNGC_STATUS_FIFO_LEVEL_SHIFT;
-
-               if (level) {
+               if (status & RNGC_STATUS_FIFO_LEVEL_MASK) {
                        /* retrieve a random number from FIFO */
                        *(u32 *)data = readl(rngc->base + RNGC_FIFO);