From faf22b13ee7335129e236804b0e532b1872d1fd8 Mon Sep 17 00:00:00 2001 From: Antti Palosaari Date: Wed, 29 Apr 2015 13:13:31 -0300 Subject: [media] msi2500: 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/usb/msi2500/msi2500.c | 49 +++++++++++++++++++++++++------------ 1 file changed, 34 insertions(+), 15 deletions(-) (limited to 'drivers/media/usb/msi2500') diff --git a/drivers/media/usb/msi2500/msi2500.c b/drivers/media/usb/msi2500/msi2500.c index efc761c78f72..8605b96dc0b4 100644 --- a/drivers/media/usb/msi2500/msi2500.c +++ b/drivers/media/usb/msi2500/msi2500.c @@ -682,11 +682,10 @@ static int msi2500_ctrl_msg(struct msi2500_state *s, u8 cmd, u32 data) return ret; } -#define F_REF 24000000 -#define DIV_R_IN 2 static int msi2500_set_usb_adc(struct msi2500_state *s) { - int ret, div_n, div_m, div_r_out, f_sr, f_vco, fract; + int ret; + unsigned int f_vco, f_sr, div_n, k, k_cw, div_out; u32 reg3, reg4, reg7; struct v4l2_ctrl *bandwidth_auto; struct v4l2_ctrl *bandwidth; @@ -727,6 +726,21 @@ static int msi2500_set_usb_adc(struct msi2500_state *s) break; } + /* + * Fractional-N synthesizer + * + * +----------------------------------------+ + * v | + * Fref +----+ +-------+ +-----+ +------+ +---+ + * ------> | PD | --> | VCO | --> | /2 | ------> | /N.F | <-- | K | + * +----+ +-------+ +-----+ +------+ +---+ + * | + * | + * v + * +-------+ +-----+ Fout + * | /Rout | --> | /12 | ------> + * +-------+ +-----+ + */ /* * Synthesizer config is just a educated guess... * @@ -754,10 +768,14 @@ static int msi2500_set_usb_adc(struct msi2500_state *s) * * VCO 202000000 - 720000000++ */ + + #define F_REF 24000000 + #define DIV_PRE_N 2 + #define DIV_LO_OUT 12 reg3 = 0x01000303; reg4 = 0x00000004; - /* XXX: Filters? AGC? */ + /* XXX: Filters? AGC? VCO band? */ if (f_sr < 6000000) reg3 |= 0x1 << 20; else if (f_sr < 7000000) @@ -767,24 +785,25 @@ static int msi2500_set_usb_adc(struct msi2500_state *s) else reg3 |= 0xd << 20; - for (div_r_out = 4; div_r_out < 16; div_r_out += 2) { - f_vco = f_sr * div_r_out * 12; - dev_dbg(s->dev, "div_r_out=%d f_vco=%d\n", div_r_out, f_vco); + for (div_out = 4; div_out < 16; div_out += 2) { + f_vco = f_sr * div_out * DIV_LO_OUT; + dev_dbg(s->dev, "div_out=%d f_vco=%d\n", div_out, f_vco); if (f_vco >= 202000000) break; } - div_n = f_vco / (F_REF * DIV_R_IN); - div_m = f_vco % (F_REF * DIV_R_IN); - fract = 0x200000ul * div_m / (F_REF * DIV_R_IN); + /* Calculate PLL integer and fractional control word. */ + div_n = div_u64_rem(f_vco, DIV_PRE_N * F_REF, &k); + k_cw = div_u64((u64) k * 0x200000, DIV_PRE_N * F_REF); reg3 |= div_n << 16; - reg3 |= (div_r_out / 2 - 1) << 10; - reg3 |= ((fract >> 20) & 0x000001) << 15; /* [20] */ - reg4 |= ((fract >> 0) & 0x0fffff) << 8; /* [19:0] */ + reg3 |= (div_out / 2 - 1) << 10; + reg3 |= ((k_cw >> 20) & 0x000001) << 15; /* [20] */ + reg4 |= ((k_cw >> 0) & 0x0fffff) << 8; /* [19:0] */ - dev_dbg(s->dev, "f_sr=%d f_vco=%d div_n=%d div_m=%d div_r_out=%d reg3=%08x reg4=%08x\n", - f_sr, f_vco, div_n, div_m, div_r_out, reg3, reg4); + dev_dbg(s->dev, + "f_sr=%u f_vco=%u div_n=%u k=%u div_out=%u reg3=%08x reg4=%08x\n", + f_sr, f_vco, div_n, k, div_out, reg3, reg4); ret = msi2500_ctrl_msg(s, CMD_WREG, 0x00608008); if (ret) -- cgit v1.2.3