Hi,
On Thursday 13 June 2013 04:51 PM, Inki Dae wrote:
-----Original Message-----
From: Sylwester Nawrocki [mailto:s.nawrocki@xxxxxxxxxxx]
Sent: Thursday, June 13, 2013 5:56 PM
To: Rahul Sharma
Cc: Rahul Sharma; Inki Dae; linux-samsung-soc@xxxxxxxxxxxxxxx; devicetree-
discuss@xxxxxxxxxxxxxxxx; DRI mailing list; Kukjin Kim; Seung-Woo Kim;
Sean Paul; sunil joshi; Kishon Vijay Abraham I; Stephen Warren;
grant.likely@xxxxxxxxxx
Subject: Re: [RFC 0/2] exynos5250/hdmi: replace dummy hdmiphy clock with
pmu reg control
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.
Yeah, at least, it seems that we could use PHY module to control PMU
register, HDMI_PHY_CONTROL. However, PHY module provides only init/on/off
callbacks. As you may know, HDMIPHY needs i2c interfaces to control HDMIPHY
clock. So with PHY module, HDMIPHY driver could enable PMU more generically,
but also has to use existing i2c stuff to control HDMIPHY clock. I had a
quick review to Generic PHY Framework[v6] but I didn't see that the PHY
module could generically support more features such as i2c stuff.
I don't think PHY framework needs to provide i2c interfaces to program
certain configurations. Instead in one of the callbacks (init/on/off)
PHY driver can program whatever it wants using any of the interfaces it
needs. IMO PHY framework should work independent of the interfaces.
For example, twl4030 phy driver actually uses i2c to program its
registers but still it uses the PHY framework [1].
[1] --> http://www.gossamer-threads.com/lists/linux/kernel/1729414
Thanks
Kishon
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