V4L/DVB (6654): mt352: support oversampled IF input

Rework the input frequency calculation so that it produces the right values
when the ADC oversamples the IF input.

This means MT352 devices can now process a near-zero IF (according to the,
specs 4.57MHz is supported with the default crystal).

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/media/dvb/frontends/mt352.c b/drivers/media/dvb/frontends/mt352.c
index 5dd9b731f6f2..7cd190b6f015 100644
--- a/drivers/media/dvb/frontends/mt352.c
+++ b/drivers/media/dvb/frontends/mt352.c
@@ -152,7 +152,13 @@ static void mt352_calc_input_freq(struct mt352_state* state,
         if (state->config.if2)
                 if2 = state->config.if2;
 
-        ife = (2*adc_clock - if2);
+        if (adc_clock >= if2 * 2)
+                ife = if2;
+        else {
+                ife = adc_clock - (if2 % adc_clock);
+                if (ife > adc_clock / 2)
+                        ife = adc_clock - ife;
+        }
         value = -16374 * ife / adc_clock;
         dprintk("%s: if2 %d, ife %d, adc_clock %d => %d / 0x%x\n",
                 __FUNCTION__, if2, ife, adc_clock, value, value & 0x3fff);