On Sun, Sep 27, 2009 at 12:25 PM, Michael Krufky <[email protected]> wrote:
> On Thu, Sep 24, 2009 at 5:42 PM, <[email protected]> wrote:
>> On Thu, Sep 24, 2009 at 02:46:06PM -0400, Michael Krufky wrote:
>>> On Tue, Sep 22, 2009 at 5:05 PM, <[email protected]> wrote:
>>> >
>>> > Multiplication by 62500 causes an overflow in the 32 bits "freq" register
>>> > when
>>> > using radio. FM radio reception on a Zolid Hybrid PCI is now working.
>>> > Other
>>> > tda18271 configurations may also benefit from this change ;)
>>> >
>>> > Signed-off-by: [email protected]
>>> >
>>> > diff -r 29e4ba1a09bc linux/drivers/media/common/tuners/tda18271-fe.c
>> ...
>>> > - freq = freq / 1000;
>>> > + freq = params->frequency * 625;
>>> > + freq = freq / 10;
>>
>> Hmm now that I review my own patch:
>>
>> - freq = freq / 1000;
>> + freq = params->frequency * 125;
>> + freq = freq / 2;
>>
>> might even be better...
>
> Henk,
>
> That certainly is better, but I am going to go with an even simpler &
> cleaner approach:
>
> diff -r f52640ced9e8 linux/drivers/media/common/tuners/tda18271-fe.c
> --- a/linux/drivers/media/common/tuners/tda18271-fe.c Tue Sep 15
> 01:25:35 2009 -0400
> +++ b/linux/drivers/media/common/tuners/tda18271-fe.c Sun Sep 27
> 12:21:37 2009 -0400
> @@ -1001,12 +1001,12 @@
> struct tda18271_std_map_item *map;
> char *mode;
> int ret;
> - u32 freq = params->frequency * 62500;
> + u32 freq = params->frequency *
> + ((params->mode == V4L2_TUNER_RADIO) ? 125 / 2 : 62500);
>
> priv->mode = TDA18271_ANALOG;
>
> if (params->mode == V4L2_TUNER_RADIO) {
> - freq = freq / 1000;
> map = &std_map->fm_radio;
> mode = "fm";
> } else if (params->std & V4L2_STD_MN) {
>
>
> You still get the credit for spotting the problem & providing the
> original fix -- thanks again! I'm going to push this along with the
> others today.
On a second thought, I see that my above patch loses some precision
... this is even better:
diff -r f52640ced9e8 linux/drivers/media/common/tuners/tda18271-fe.c
--- a/linux/drivers/media/common/tuners/tda18271-fe.c Tue Sep 15
01:25:35 2009 -0400
+++ b/linux/drivers/media/common/tuners/tda18271-fe.c Sun Sep 27
12:33:20 2009 -0400
@@ -1001,12 +1001,12 @@
struct tda18271_std_map_item *map;
char *mode;
int ret;
- u32 freq = params->frequency * 62500;
+ u32 freq = params->frequency * 125 *
+ ((params->mode == V4L2_TUNER_RADIO) ? 1 : 1000) / 2;
priv->mode = TDA18271_ANALOG;
if (params->mode == V4L2_TUNER_RADIO) {
- freq = freq / 1000;
map = &std_map->fm_radio;
mode = "fm";
} else if (params->std & V4L2_STD_MN) {
Cheers,
Mike
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