V4L/DVB (9449): Code Simplification: use do_div() instead

Signed-off-by: Reinhard Nissl <rnissl@gmx.de>
Signed-off-by: Manu Abraham <manu@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 34 insertions, 35 deletions

diff --git a/drivers/media/dvb/frontends/stb0899_algo.c b/drivers/media/dvb/frontends/stb0899_algo.c
index 2d2b87cf6d00..f1432cb29262 100644
--- a/drivers/media/dvb/frontends/stb0899_algo.c
+++ b/drivers/media/dvb/frontends/stb0899_algo.c
@@ -23,27 +23,12 @@
 #include "stb0899_priv.h"
 #include "stb0899_reg.h"
 
-/*
- * BinaryFloatDiv
- * float division with integer
- */
-static long BinaryFloatDiv(long n1, long n2, int precision)
+inline u32 stb0899_do_div(u64 n, u32 d)
 {
-        int i = 0;
-        long result = 0;
+        /* wrap do_div() for ease of use */
 
-        while (i <= precision) {
-                if (n1 < n2) {
-                        result *= 2;
-                        n1 *= 2;
-                } else {
-                        result = result * 2 + 1;
-                        n1 = (n1 - n2) * 2;
-                }
-                i++;
-        }
-
-        return result;
+        do_div(n, d);
+        return n;
 }
 
 /*
@@ -52,15 +37,15 @@ static long BinaryFloatDiv(long n1, long n2, int precision)
  */
 static u32 stb0899_calc_srate(u32 master_clk, u8 *sfr)
 {
-        u32 tmp, tmp2, mclk;
+        u64 tmp;
 
-        mclk  =  master_clk / 4096L; /* MasterClock * 10 / 2^20 */
-        tmp  = (((u32) sfr[0] << 12) + ((u32) sfr[1] << 4)) / 16;
+        /* srate = (SFR * master_clk) >> 20 */
 
-        tmp *= mclk;
-        tmp /= 16;
-        tmp2 = ((u32) sfr[2] * mclk) / 256;
-        tmp += tmp2;
+        /* sfr is of size 20 bit, stored with an offset of 4 bit */
+        tmp = (((u32)sfr[0]) << 16) | (((u32)sfr[1]) << 8) | sfr[2];
+        tmp &= ~0xf;
+        tmp *= master_clk;
+        tmp >>= 24;
 
         return tmp;
 }
@@ -72,7 +57,7 @@ static u32 stb0899_calc_srate(u32 master_clk, u8 *sfr)
 u32 stb0899_get_srate(struct stb0899_state *state)
 {
         struct stb0899_internal *internal = &state->internal;
-        u8 sfr[4];
+        u8 sfr[3];
 
         stb0899_read_regs(state, STB0899_SFRH, sfr, 3);
 
@@ -101,16 +86,30 @@ static u32 stb0899_set_srate(struct stb0899_state *state, u32 master_clk, u32 sr
          */
 //      srate_up += (srate_up * 3) / 100;
 
-        tmp = BinaryFloatDiv(srate, master_clk, 20);
-//      tmp_up = BinaryFloatDiv(srate_up, master_clk, 20);
+        /*
+         * srate = (SFR * master_clk) >> 20
+         *      <=>
+         *   SFR = srate << 20 / master_clk
+         *
+         * rounded:
+         *   SFR = (srate << 21 + master_clk) / (2 * master_clk)
+         *
+         * stored as 20 bit number with an offset of 4 bit:
+         *   sfr = SFR << 4;
+         */
+//      tmp_up = stb0899_do_div((((u64)srate_up) << 21) + master_clk, 2 * master_clk);
+//      tmp_up <<= 4;
+
+        tmp = stb0899_do_div((((u64)srate) << 21) + master_clk, 2 * master_clk);
+        tmp <<= 4;
 
-//      sfr_up[0] = (tmp_up >> 12) & 0xff;
-//      sfr_up[1] = (tmp_up >>  4) & 0xff;
-//      sfr_up[2] =  tmp_up & 0x0f;
+//      sfr_up[0] = tmp_up >> 16;
+//      sfr_up[1] = tmp_up >>  8;
+//      sfr_up[2] = tmp_up;
 
-        sfr[0] = (tmp >> 12) & 0xff;
-        sfr[1] = (tmp >>  4) & 0xff;
-        sfr[2] = (tmp <<  4) & 0xf0;
+        sfr[0] = tmp >> 16;
+        sfr[1] = tmp >>  8;
+        sfr[2] = tmp;
 
 //      stb0899_write_regs(state, STB0899_SFRUPH, sfr_up, 3);
         stb0899_write_regs(state, STB0899_SFRH, sfr, 3);