[PATCH] i2c: rk3x: Give the tuning value 0 during rk3x_i2c_v0_calc_timings

[PATCH] i2c: rk3x: Give the tuning value 0 during rk3x_i2c_v0_calc_timings

[David Wu]

We found a bug that i2c transfer sometimes failed on 3066a board with
stabel-4.8, the con register would be updated by uninitialized tuning
value, it made the i2c transfer failed.

So give the tuning value to be zero during rk3x_i2c_v0_calc_timings.

Signed-off-by: David Wu <david.wu@rock-chips.com>
---
 drivers/i2c/busses/i2c-rk3x.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
index 50702c7..df22066 100644
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -694,6 +694,8 @@ static int rk3x_i2c_v0_calc_timings(unsigned long clk_rate,
 	t_calc->div_low--;
 	t_calc->div_high--;
 
+	/* Give the tuning value 0, that would not update con register */
+	t_calc->tuning = 0;
 	/* Maximum divider supported by hw is 0xffff */
 	if (t_calc->div_low > 0xffff) {
 		t_calc->div_low = 0xffff;
-- 
1.9.1

Re: [PATCH] i2c: rk3x: Give the tuning value 0 during rk3x_i2c_v0_calc_timings

[Andy Yan]

Hi:


On 2016年10月22日 16:43, David Wu wrote:
> We found a bug that i2c transfer sometimes failed on 3066a board with
> stabel-4.8, the con register would be updated by uninitialized tuning
> value, it made the i2c transfer failed.
>
> So give the tuning value to be zero during rk3x_i2c_v0_calc_timings.
>
> Signed-off-by: David Wu <david.wu@rock-chips.com>
> ---
>   drivers/i2c/busses/i2c-rk3x.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> index 50702c7..df22066 100644
> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c
> @@ -694,6 +694,8 @@ static int rk3x_i2c_v0_calc_timings(unsigned long clk_rate,
>   	t_calc->div_low--;
>   	t_calc->div_high--;
>   
> +	/* Give the tuning value 0, that would not update con register */
> +	t_calc->tuning = 0;
>   	/* Maximum divider supported by hw is 0xffff */
>   	if (t_calc->div_low > 0xffff) {
>   		t_calc->div_low = 0xffff;

rk3066a based board can't boot up(with endless i2c irq messages print 
out) from linux-4.8 without this fix.

Tested-by: Andy Yan <andy.yan@rock-chips.com>

Re: [PATCH] i2c: rk3x: Give the tuning value 0 during rk3x_i2c_v0_calc_timings

[Doug Anderson]

Hi,

On Sat, Oct 22, 2016 at 1:43 AM, David Wu <david.wu@rock-chips.com> wrote:
> We found a bug that i2c transfer sometimes failed on 3066a board with
> stabel-4.8, the con register would be updated by uninitialized tuning
> value, it made the i2c transfer failed.
>
> So give the tuning value to be zero during rk3x_i2c_v0_calc_timings.
>
> Signed-off-by: David Wu <david.wu@rock-chips.com>
> ---
>  drivers/i2c/busses/i2c-rk3x.c | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Douglas Anderson <dianders@chromium.org>

Re: [PATCH] i2c: rk3x: Give the tuning value 0 during rk3x_i2c_v0_calc_timings

[Wolfram Sang]

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On Sat, Oct 22, 2016 at 04:43:42PM +0800, David Wu wrote:
> We found a bug that i2c transfer sometimes failed on 3066a board with
> stabel-4.8, the con register would be updated by uninitialized tuning
> value, it made the i2c transfer failed.
> 
> So give the tuning value to be zero during rk3x_i2c_v0_calc_timings.
> 
> Signed-off-by: David Wu <david.wu@rock-chips.com>

Added stable and applied to for-current, thanks!


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Re: [PATCH] i2c: rk3x: Give the tuning value 0 during rk3x_i2c_v0_calc_timings

[Wolfram Sang]

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On Sat, Oct 22, 2016 at 04:43:42PM +0800, David Wu wrote:
> We found a bug that i2c transfer sometimes failed on 3066a board with
> stabel-4.8, the con register would be updated by uninitialized tuning
> value, it made the i2c transfer failed.
> 
> So give the tuning value to be zero during rk3x_i2c_v0_calc_timings.
> 
> Signed-off-by: David Wu <david.wu@rock-chips.com>

What I missed to say in my review:

Please use a subject line that describes WHY the change is needed not so
much WHAT is done. Like: "fix missing initialization causing boot
problems"


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