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[media] e4000: revise synthesizer calculation 

Update synthesizer calculation to model I prefer nowadays. It is
mostly just renaming some variables to ones I think are most standard.
Also add 'schematic' of synthesizer following my current understanding.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Antti Palosaari 2015-04-21 21:18:45 -03:00 committed by Mauro Carvalho Chehab
parent e4d131d392
commit 0e3a71c374
2 changed files with 34 additions and 16 deletions
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46
drivers/media/tuners/e4000.c
View File

@ -115,8 +115,8 @@ 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];
@ -129,7 +129,21 @@ 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;
@ -140,18 +154,22 @@ 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;
#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,
"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;
dev_dbg(&s->client->dev, "f_vco=%llu pll div=%d sigma_delta=%04x\n",
f_vco, buf[0], sigma_delta);
buf[4] = e4000_pll_lut[i].div_out_reg;
ret = regmap_bulk_write(s->regmap, 0x09, buf, 5);
if (ret)
goto err;

4
drivers/media/tuners/e4000_priv.h
View File

@ -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[] = {