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/usb/msi2500/msi2500.c | 49 +++++++++++++++++++++++++------------
1 file changed, 34 insertions(+), 15 deletions(-)
diff --git a/drivers/media/usb/msi2500/msi2500.c b/drivers/media/usb/msi2500/msi2500.c
index efc761c..8605b96 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;
@@ -728,6 +727,21 @@ static int msi2500_set_usb_adc(struct msi2500_state *s)
}
/*
+ * Fractional-N synthesizer
+ *
+ * +----------------------------------------+
+ * v |
+ * Fref +----+ +-------+ +-----+ +------+ +---+
+ * ------> | PD | --> | VCO | --> | /2 | ------> | /N.F | <-- | K |
+ * +----+ +-------+ +-----+ +------+ +---+
+ * |
+ * |
+ * v
+ * +-------+ +-----+ Fout
+ * | /Rout | --> | /12 | ------>
+ * +-------+ +-----+
+ */
+ /*
* Synthesizer config is just a educated guess...
*
* [7:0] 0x03, register address
@@ -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)
--
http://palosaari.fi/
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