Add schematic drawing of used Fractional-N PLL. Rename and add some
new PLL variables for better understanding.
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
drivers/media/tuners/e4000.c | 44 +++++++++++++++++++++++++++------------
drivers/media/tuners/e4000_priv.h | 4 ++--
2 files changed, 33 insertions(+), 15 deletions(-)
diff --git a/drivers/media/tuners/e4000.c b/drivers/media/tuners/e4000.c
index a5d51d7..d27d2e7 100644
--- a/drivers/media/tuners/e4000.c
+++ b/drivers/media/tuners/e4000.c
@@ -112,8 +112,8 @@ static int e4000_set_params(struct dvb_frontend *fe)
{
struct e4000 *s = fe->tuner_priv;
struct dtv_frontend_properties *c = &fe->dtv_property_cache;
- int ret, i, sigma_delta;
- unsigned int pll_n, pll_f;
+ int ret, i;
+ unsigned int div_n, k, k_cw, div_out;
u64 f_vco;
u8 buf[5], i_data[4], q_data[4];
@@ -126,7 +126,21 @@ static int e4000_set_params(struct dvb_frontend *fe)
if (ret)
goto err;
- /* PLL */
+ /*
+ * Fractional-N synthesizer
+ *
+ * +----------------------------+
+ * v |
+ * Fref +----+ +-------+ +------+ +---+
+ * ------> | PD | --> | VCO | ------> | /N.F | <-- | K |
+ * +----+ +-------+ +------+ +---+
+ * |
+ * |
+ * v
+ * +-------+ Fout
+ * | /Rout | ------>
+ * +-------+
+ */
for (i = 0; i < ARRAY_SIZE(e4000_pll_lut); i++) {
if (c->frequency <= e4000_pll_lut[i].freq)
break;
@@ -137,18 +151,22 @@ static int e4000_set_params(struct dvb_frontend *fe)
goto err;
}
- f_vco = 1ull * c->frequency * e4000_pll_lut[i].mul;
- pll_n = div_u64_rem(f_vco, s->clock, &pll_f);
- sigma_delta = div_u64(0x10000ULL * pll_f, s->clock);
- buf[0] = pll_n;
- buf[1] = (sigma_delta >> 0) & 0xff;
- buf[2] = (sigma_delta >> 8) & 0xff;
- buf[3] = 0x00;
- buf[4] = e4000_pll_lut[i].div;
+ #define F_REF s->clock
+ div_out = e4000_pll_lut[i].div_out;
+ f_vco = (u64) c->frequency * div_out;
+ /* calculate PLL integer and fractional control word */
+ div_n = div_u64_rem(f_vco, F_REF, &k);
+ k_cw = div_u64((u64) k * 0x10000, F_REF);
- dev_dbg(&s->client->dev, "f_vco=%llu pll div=%d sigma_delta=%04x\n",
- f_vco, buf[0], sigma_delta);
+ dev_dbg(&s->client->dev,
+ "frequency=%u f_vco=%llu F_REF=%u div_n=%u k=%u k_cw=%04x div_out=%u\n",
+ c->frequency, f_vco, F_REF, div_n, k, k_cw, div_out);
+ buf[0] = div_n;
+ buf[1] = (k_cw >> 0) & 0xff;
+ buf[2] = (k_cw >> 8) & 0xff;
+ buf[3] = 0x00;
+ buf[4] = e4000_pll_lut[i].div_out_reg;
ret = regmap_bulk_write(s->regmap, 0x09, buf, 5);
if (ret)
goto err;
diff --git a/drivers/media/tuners/e4000_priv.h b/drivers/media/tuners/e4000_priv.h
index cb00704..6214fc0 100644
--- a/drivers/media/tuners/e4000_priv.h
+++ b/drivers/media/tuners/e4000_priv.h
@@ -49,8 +49,8 @@ struct e4000 {
struct e4000_pll {
u32 freq;
- u8 div;
- u8 mul;
+ u8 div_out_reg;
+ u8 div_out;
};
static const struct e4000_pll e4000_pll_lut[] = {
--
http://palosaari.fi/
--
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