Re: [RFC 0/2] exynos5250/hdmi: replace dummy hdmiphy clock with pmu reg control

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

Hi,

On 06/13/2013 06:26 AM, Rahul Sharma wrote:
> Mr. Dae,
> 
> Thanks for your valuable inputs.
> 
> I posted it as RFC because, I also have received comments to register
> hdmiphy as a clock controller. As we always configure it for specific
> frequency, hdmi-phy looks similar to a PLL. But it really doesn't
> belong to that class. Secondly prior to exynos5420, it was a i2c
> device. I am not sure we can register a I2C device as a clock
> controller. I wanted to discuss and explore this option here.

Have you considered using the generic PHY framework for those HDMI 
PHY devices [1] ? I guess we could add a dedicated group of ops for 
video PHYs, similarly as is is done with struct v4l2_subdev_ops. For
configuring things like the carrier/pixel clock frequency or anything 
what's common across the video PHYs.

Perhaps you could have a look and see if this framework would be 
useful for HDMI and possibly point out anything what might be missing ?
 
I'm not sure it it really solves the issues specific to the Exynos 
HDMI but at least with a generic PHY driver the PHY module would be 
separate from the PHY controller, as often same HDMI DPHY can be used 
with various types of a HDMI controller. So this would allow to not 
duplicate the HDMI PHY drivers in the long-term perspective.

[1] https://lkml.org/lkml/2013/4/29/95

Thanks,
Sylwester

> As you said, in parallel, I will align these changes and along with
> "drm/exynos: hdmi: move hdmiphy related code to hdmiphy driver"
> series and post them.
> 
> I hope we should be able to close on one of the above approaches for
> hdmiphy.
> 
> regards,
> Rahul Sharma.
> 
> On Wed, Jun 12, 2013 at 9:57 AM, Inki Dae <inki.dae@samsung.com> wrote:
>>
>> 2013/6/12 Inki Dae <inki.dae@samsung.com>
>>>
>>> Hi Rahul,
>>>
>>> This patch is important to us. Actually, previous hdmi driver had
>>> controlled hdmiphy HDMI_PHY_CONTROL as if that were a clock but now that
>>> doesn't exist anymore. So we need to discuss how hdmiphy should be handled.
>>> I konw that you had already posted hdmiphy relevant patch set, [PATCH 0/4]
>>> drm/exynos: hdmi: move hdmiphy related code to hdmiphy driver.
>>>
>>> I think we can couple pmu register controlling codes with that patch set
>>> without RFC. Could you update and post them again? like below,
>>> [PATCH 0/4] drm/exynos: hdmi: move hdmiphy related code to hdmiphy driver
>>> + [RFC 0/2] exynos5250/hdmi: replace dummy hdmiphy clock with pmu reg
>>> control
>>>
>>> And then let's start review :)
>>
>> And I think It would be better to move the pmu register controlling codes
>> into hdmiphy driver like drivers/usb/phy/phy-samsung-usb2.c driver does.
>>>
>>> Thanks,
>>> Inki Dae
>>>
>>> 2013/6/11 Rahul Sharma <rahul.sharma@samsung.com>
>>>>
>>>> Previously, hdmiphy is added as a dummy clock in clock file for
>>>> exynos SoCs. Enable/Disable to this clock, actually toggles the power
>>>> control bit in PMU, instead of controlling the clock gate.
>>>>
>>>> This RFC adds the support to parse hdmiphy control node which is a child
>>>> node to hdmi, and map the pmu register to toggle the power control bit.
>>>>
>>>> This is based on drm-next branch in Inki Dae's tree.
>>>>
>>>> Rahul Sharma (2):
>>>>   drm/exynos: replace dummy hdmiphy clock with pmu register control
>>>>   ARM/dts: add hdmiphy power control pmu register to hdmi dt node
>>>>
>>>>  arch/arm/boot/dts/exynos5250.dtsi    |    6 +++
>>>>  drivers/gpu/drm/exynos/exynos_hdmi.c |   69
>>>> ++++++++++++++++++++++++++++++----
>>>>  drivers/gpu/drm/exynos/regs-hdmi.h   |    4 ++
>>>>  3 files changed, 71 insertions(+), 8 deletions(-)
>>>>
>>>> --
>>>> 1.7.10.4

-- 
Sylwester Nawrocki
Samsung R&D Institute Poland
Samsung Electronics