Re: [RFC v2 PATCH 02/14] drm/exynos: dsi: delay setting clocks after reset

YoungJun Cho
2014-04-23T03:45:00Z

Hi again Andrzej,

On 04/23/2014 10:01 AM, YoungJun Cho wrote:
> Hi Andrzej
>
> Thank you for comments.
>
> On 04/22/2014 09:15 PM, Andrzej Hajda wrote:
>> Hi YoungJun,
>>
>> On 04/21/2014 02:28 PM, YoungJun Cho wrote:
>>> Some phy control registers are not kept after software reset.
>>> So this patch makes the clocks containing phy control to be set
>>> after software reset.
>>>
>>> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
>>> Acked-by: Inki Dae <inki.dae@samsung.com>
>>> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
>>> ---
>>> drivers/gpu/drm/exynos/exynos_drm_dsi.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>>> b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>>> index 956e5f3..2cf1f0b 100644
>>> --- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>>> +++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>>> @@ -946,10 +946,10 @@ static irqreturn_t exynos_dsi_irq(int irq, void
>>> *dev_id)
>>>
>>> static int exynos_dsi_init(struct exynos_dsi *dsi)
>>> {
>>> - exynos_dsi_enable_clock(dsi);
>>> exynos_dsi_reset(dsi);
>>> enable_irq(dsi->irq);
>>> exynos_dsi_wait_for_reset(dsi);
>>> + exynos_dsi_enable_clock(dsi);
>>> exynos_dsi_init_link(dsi);
>>>
>>> return 0;
>>
>> I have commented it in the previous version of the patchset. I repeat it
>> again.
>> This is a regression, on exynos4210-trats I have 'timeout waiting for
>> reset' message after dpms off, on.
>
> I'm really sorry for that. I misunderstood last time.
>
> I think the original codes were correct, because the reset timeout would
> be occurred without clock activation.

This is not true.

>
> I'll check and fix again.
> (By the way, why am I ok?)

I have not verified with exynos4210-trats board yet(I have to get it),
but reset timeout is occured in exynos_dsi_wait_for_reset()
with &dsi->completed and that is completed by exynos_dsi_irq().

And the regulators and clocks are enabled by exynos_dsi_poweron(),
NOT by exynos_dsi_enable_clock().

So I think the reset timeout is not related with this patch.

Anyway I need more investigation.

Thank you.
Best regards YJ

>
>>
>> I will comment your previous answer here to make the discussion easier:
>>> As I mentioned in description, it came from phy control registers.
>>> Fortunately Exynos4 SoCs are safe, but the DSIM_PHYCTRL_REG,
>>> DSIM_PHYTIMING_REG, DSIM_PHYTIMING1_REG and DSIM_PHYTIMING2_REG are
>>> affected which are used in exynos_dsi_set_pll() for Exynos5 SoCs.
>>>
>>> So this patch is required for Exynos5 SoCs.
>>
>> In the moment this patch is applied exynos_dsi_set_pll do not touch phy
>> registers you have mentioned.
>> Your change would be more clear if it will be merged together with the
>> patch adding PHYCTRL settings.
>>
>> Anyway, solution is simple - please set PHY registers after reset and
>> configure clocks before reset to avoid
>> reset timeouts, is there any reason to not do it this way?
>
> The only reason is that the PHY control is related with PLL control and
> that was in exynos_dsi_enable_clock() call path.
> So I just wanted to keep current sequence.
>
> If there is no way to use previous one, I'll consider your approach.
>
> Thank you.
> Best regards YJ
>
>>
>> Regards
>> Andrzej
>>
>
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