Re: [PATCH v2] i2c: i2c-bcm2708: fixes cdiv uneven number

[rajeev kumar <rajeevkumar.linux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Sat, May 2, 2015 at 3:13 AM, Silvan Wicki <linux_wi-ADq4ffItWIY@public.gmane.org> wrote:
> Prevents that cdiv can be an uneven number as per datasheet cdiv is
> always rounded down to an even number.
>
> Datasheet at page 34 on
> http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
>
> Signed-off-by: Silvan Wicki <linux_wi-ADq4ffItWIY@public.gmane.org>
> ---
Reviewed-by: Rajeev Kumar <rajeevkumar.linux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

>  drivers/i2c/busses/i2c-bcm2708.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-bcm2708.c b/drivers/i2c/busses/i2c-bcm2708.c
> index 81e9374..dd7094a 100644
> --- a/drivers/i2c/busses/i2c-bcm2708.c
> +++ b/drivers/i2c/busses/i2c-bcm2708.c
> @@ -67,6 +67,9 @@
>  #define BSC_S_DONE             0x00000002
>  #define BSC_S_TA               0x00000001
>
> +#define BSC_CDIV_MAX           0xFFFE
> +#define BSC_CDIV_BITMASK       0xEFFF
> +
>  #define I2C_TIMEOUT_MS 150
>  #define I2C_WAIT_LOOP_COUNT 40
>
> @@ -441,9 +444,15 @@ static int bcm2708_i2c_probe(struct platform_device *pdev)
>
>         bus_hz = clk_get_rate(bi->clk);
>         cdiv = bus_hz / baudrate;
> -       if (cdiv > 0xffff) {
> -               cdiv = 0xffff;
> +       /* as per datasheet cdiv is always rounded down to an even number */
> +       if (cdiv > BSC_CDIV_MAX) {
> +               cdiv = BSC_CDIV_MAX;
>                 baudrate = bus_hz / cdiv;
> +       } else {
> +               if ((cdiv & BSC_CDIV_BITMASK) != cdiv) {
> +                       cdiv &= BSC_CDIV_BITMASK;
> +                       baudrate = bus_hz / cdiv;
> +               }
>         }
>         bi->cdiv = cdiv;
>
> --
> 2.1.4
>
> --
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