Update synthesizer calculation to model I prefer nowadays. It is mostly
just renaming some variables, but also minor functionality change how
integer and fractional part are divided (using div_u64_rem()). Also, add
'schematic' of synthesizer following my current understanding.
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
drivers/media/tuners/msi001.c | 74 +++++++++++++++++++++++++------------------
1 file changed, 44 insertions(+), 30 deletions(-)
diff --git a/drivers/media/tuners/msi001.c b/drivers/media/tuners/msi001.c
index 74cfc3c..d0ec4e3 100644
--- a/drivers/media/tuners/msi001.c
+++ b/drivers/media/tuners/msi001.c
@@ -91,15 +91,15 @@ err:
static int msi001_set_tuner(struct msi001 *s)
{
int ret, i;
- unsigned int n, m, thresh, frac, vco_step, tmp, f_if1;
+ unsigned int uitmp, div_n, k, k_thresh, k_frac, div_lo, f_if1;
u32 reg;
- u64 f_vco, tmp64;
- u8 mode, filter_mode, lo_div;
+ u64 f_vco;
+ u8 mode, filter_mode;
static const struct {
u32 rf;
u8 mode;
- u8 lo_div;
+ u8 div_lo;
} band_lut[] = {
{ 50000000, 0xe1, 16}, /* AM_MODE2, antenna 2 */
{108000000, 0x42, 32}, /* VHF_MODE */
@@ -144,15 +144,15 @@ static int msi001_set_tuner(struct msi001 *s)
*/
unsigned int f_if = 0;
#define F_REF 24000000
- #define R_REF 4
- #define F_OUT_STEP 1
+ #define DIV_PRE_N 4
+ #define F_VCO_STEP div_lo
dev_dbg(&s->spi->dev, "f_rf=%d f_if=%d\n", f_rf, f_if);
for (i = 0; i < ARRAY_SIZE(band_lut); i++) {
if (f_rf <= band_lut[i].rf) {
mode = band_lut[i].mode;
- lo_div = band_lut[i].lo_div;
+ div_lo = band_lut[i].div_lo;
break;
}
}
@@ -200,32 +200,46 @@ static int msi001_set_tuner(struct msi001 *s)
dev_dbg(&s->spi->dev, "bandwidth selected=%d\n", bandwidth_lut[i].freq);
- f_vco = (u64) (f_rf + f_if + f_if1) * lo_div;
- tmp64 = f_vco;
- m = do_div(tmp64, F_REF * R_REF);
- n = (unsigned int) tmp64;
+ /*
+ * Fractional-N synthesizer
+ *
+ * +---------------------------------------+
+ * v |
+ * Fref +----+ +-------+ +----+ +------+ +---+
+ * ------> | PD | --> | VCO | ------> | /4 | --> | /N.F | <-- | K |
+ * +----+ +-------+ +----+ +------+ +---+
+ * |
+ * |
+ * v
+ * +-------+ Fout
+ * | /Rout | ------>
+ * +-------+
+ */
- vco_step = F_OUT_STEP * lo_div;
- thresh = (F_REF * R_REF) / vco_step;
- frac = 1ul * thresh * m / (F_REF * R_REF);
+ /* Calculate PLL integer and fractional control word. */
+ f_vco = (u64) (f_rf + f_if + f_if1) * div_lo;
+ div_n = div_u64_rem(f_vco, DIV_PRE_N * F_REF, &k);
+ k_thresh = (DIV_PRE_N * F_REF) / F_VCO_STEP;
+ k_frac = div_u64((u64) k * k_thresh, (DIV_PRE_N * F_REF));
/* Find out greatest common divisor and divide to smaller. */
- tmp = gcd(thresh, frac);
- thresh /= tmp;
- frac /= tmp;
+ uitmp = gcd(k_thresh, k_frac);
+ k_thresh /= uitmp;
+ k_frac /= uitmp;
/* Force divide to reg max. Resolution will be reduced. */
- tmp = DIV_ROUND_UP(thresh, 4095);
- thresh = DIV_ROUND_CLOSEST(thresh, tmp);
- frac = DIV_ROUND_CLOSEST(frac, tmp);
+ uitmp = DIV_ROUND_UP(k_thresh, 4095);
+ k_thresh = DIV_ROUND_CLOSEST(k_thresh, uitmp);
+ k_frac = DIV_ROUND_CLOSEST(k_frac, uitmp);
- /* calc real RF set */
- tmp = 1ul * F_REF * R_REF * n;
- tmp += 1ul * F_REF * R_REF * frac / thresh;
- tmp /= lo_div;
+ /* Calculate real RF set. */
+ uitmp = (unsigned int) F_REF * DIV_PRE_N * div_n;
+ uitmp += (unsigned int) F_REF * DIV_PRE_N * k_frac / k_thresh;
+ uitmp /= div_lo;
- dev_dbg(&s->spi->dev, "rf=%u:%u n=%d thresh=%d frac=%d\n",
- f_rf, tmp, n, thresh, frac);
+ dev_dbg(&s->spi->dev,
+ "f_rf=%u:%u f_vco=%llu div_n=%u k_thresh=%u k_frac=%u div_lo=%u\n",
+ f_rf, uitmp, f_vco, div_n, k_thresh, k_frac, div_lo);
ret = msi001_wreg(s, 0x00000e);
if (ret)
@@ -246,7 +260,7 @@ static int msi001_set_tuner(struct msi001 *s)
goto err;
reg = 5 << 0;
- reg |= thresh << 4;
+ reg |= k_thresh << 4;
reg |= 1 << 19;
reg |= 1 << 21;
ret = msi001_wreg(s, reg);
@@ -254,8 +268,8 @@ static int msi001_set_tuner(struct msi001 *s)
goto err;
reg = 2 << 0;
- reg |= frac << 4;
- reg |= n << 16;
+ reg |= k_frac << 4;
+ reg |= div_n << 16;
ret = msi001_wreg(s, reg);
if (ret)
goto err;
@@ -276,7 +290,7 @@ static int msi001_set_tuner(struct msi001 *s)
err:
dev_dbg(&s->spi->dev, "failed %d\n", ret);
return ret;
-};
+}
static int msi001_s_power(struct v4l2_subdev *sd, int on)
{
--
http://palosaari.fi/
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