From 9195e5b2467b258413750526d5c65c6c22fafb11 Mon Sep 17 00:00:00 2001 From: Antti Palosaari Date: Wed, 29 Apr 2015 10:10:01 -0300 Subject: [PATCH] [media] msi001: revise synthesizer calculation 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 Signed-off-by: Mauro Carvalho Chehab --- 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 74cfc3c98edb..d0ec4e3c9371 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) { -- 2.20.1