Hi Sifan,
On 27/07/15 12:47, Sifan Naeem wrote:
> After determining the minimum value for the High period (TCKH) the
> remainder of the internal clock pulses is set as the Low period (TCKL).
> This causes the i2c clock duty cycle to be much less than 50%.
>
> The fix suggested here, start with TCKH and TCKL at 50% of the internal
> clock pulses and adjusts the TCKH and TCKL values from there if the
> minimum value for TCKL is not met. This will make sure the i2c clock
> duty cycle is at 50% or close 50% whenever possible.
>
> Fixes: 27bce4 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
> Signed-off-by: Sifan Naeem <sifan.naeem@xxxxxxxxxx>
> Cc: Stable kernel (v3.19+) <stable@xxxxxxxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-img-scb.c | 30 +++++++++++++++++-------------
> 1 file changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-img-scb.c b/drivers/i2c/busses/i2c-img-scb.c
> index b4f59e1..51a5be8 100644
> --- a/drivers/i2c/busses/i2c-img-scb.c
> +++ b/drivers/i2c/busses/i2c-img-scb.c
> @@ -1178,25 +1178,29 @@ static int img_i2c_init(struct img_i2c *i2c)
> ((bitrate_khz * clk_period) / 2))
> int_bitrate++;
>
> - /* Setup TCKH value */
> - tckh = DIV_ROUND_UP(timing.tckh, clk_period);
> + /*
> + * Setup clock duty cycle, start with 50% and adjust TCKH and TCKL
> + * values from there if they don't meet minimum timing requirements
> + */
> + tckh = int_bitrate / 2;
> + tckl = int_bitrate - tckh;
too much indentation here.
Otherwise looks good to me.
Acked-by: James Hogan <james.hogan@xxxxxxxxxx>
Cheers
James
>
> - if (tckh > 0)
> - data = tckh - 1;
> - else
> - data = 0;
> + /* Adjust TCKH and TCKL values */
> + data = DIV_ROUND_UP(timing.tckl, clk_period);
>
> - img_i2c_writel(i2c, SCB_TIME_TCKH_REG, data);
> + if (tckl < data) {
> + tckl = data;
> + tckh = int_bitrate - tckl;
> + }
>
> - /* Setup TCKL value */
> - tckl = int_bitrate - tckh;
> + if (tckh > 0)
> + --tckh;
>
> if (tckl > 0)
> - data = tckl - 1;
> - else
> - data = 0;
> + --tckl;
>
> - img_i2c_writel(i2c, SCB_TIME_TCKL_REG, data);
> + img_i2c_writel(i2c, SCB_TIME_TCKH_REG, tckh);
> + img_i2c_writel(i2c, SCB_TIME_TCKL_REG, tckl);
>
> /* Setup TSDH value */
> tsdh = DIV_ROUND_UP(timing.tsdh, clk_period);
>
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