Re: [PATCH 0/4] Move DP phy switch to PHY driver

Doug Anderson
2017-12-04T16:08:39Z

Hi,

On Sun, Dec 3, 2017 at 11:46 PM, Heiko Stübner <heiko@sntech.de> wrote:
> Hi Chris,
>
> Am Montag, 4. Dezember 2017, 10:47:08 CET schrieb Chris Zhong:
>> On 2017年12月02日 05:58, Heiko Stuebner wrote:
>> > Am Freitag, 1. Dezember 2017, 13:42:46 CET schrieb Doug Anderson:
>> >> Hi,
>> >>
>> >> On Wed, Nov 29, 2017 at 6:27 PM, Chris Zhong <zyw@rock-chips.com> wrote:
>> >>> Hi Doug
>> >>>
>> >>> Thank you for mentioning this patch.
>> >>>
>> >>> I think the focus of the discussion is: can we put the grf control bit
>> >>> to
>> >>> dts.
>> >>>
>> >>> The RK3399 has 2 Type-C phy, but only one DP controller, this
>> >>> "uphy_dp_sel"
>> >>>
>> >>> can help to switch these 2 phy. So I think this bit can be considered as
>> >>> a
>> >>> part of
>> >>>
>> >>> Type-C phy, these 2 phy have different bits, just similar to other bits
>> >>> (such as "pipe-status").
>> >>>
>> >>> Put them to DTS file might be a accepted practice.
>> >>
>> >> I guess the first step would be finding the person to make a decision.
>> >> Is that Heiko? Olof? Kishon? Rob?. As I see it there are a few
>> >> options:
>> >>
>> >> 1. Land this series as-is. This makes the new bit work just like all
>> >> the other ones next to it. If anyone happens to try to use an old
>> >> device tree on a new kernel they'll break. Seems rather unlikely
>> >> given that the whole type C PHY is not really fully functional
>> >> upstream, but technically this is a no-no from a device tree
>> >> perspective.
>> >>
>> >> 2. Change the series to make this property optional. If it's not
>> >> there then the code behaves like it always did. This would address
>> >> the "compatibility" problem but likely wouldn't actually help any real
>> >> people, and it would be extra work.
>> >>
>> >> 3. Redo the driver to deprecate all the old offsets / bits and just
>> >> put the table in the driver, keyed off the compatible string and base
>> >> address if the IO memory.
>> >>
>> >>
>> >> I can't make this decision. It's up to those folks who would be
>> >> landing the patch and I'd be happy with any of them. What I'm less
>> >> happy with, however, is the indecision preventing forward progress.
>> >> We should pick one of the above things and land it. My own personal
>> >> bias is #1: just land the series. No real people will be hurt and
>> >> it's just adding another property that matches the ones next to it.
>> >
>> > I'd second that #1 . That whole type-c phy thingy never fully worked in
>> > the past (some for the never used dp output), so personally I don't have
>> > issues with going that route.
>> >
>> >> From a long term perspective (AKA how I'd write the next driver like
>> >>
>> >> this) I personally lean towards to "tables in the driver, not in the
>> >> device tree" but quite honestly I'm happy to take whatever direction
>> >> the maintainers give.
>> >
>> > It looks like we're in agreement here :-) . GRF stuff should not leak into
>> > the devicetree, as it causes endless headaches later. But I guess we'll
>> > need to live with the ones that happened so far.
>>
>> So, the first step is: move all the private property of tcphy to
>> drivers/phy/rockchip/phy-rockchip-typec.c.
>> Second step: new a member: uphy-dp-sel.
>> In my mind, we should have discussed these properties before, and then I
>> moved them all into DTS.
>
> Actually, I was agreeing with Doug, that we probably don't need to rework the
> type-c phy driver. As most properties for it are in the devicetree right now
> we'll need to support them for backwards-compatiblity anyway.
>
> And yes, there probably was discussion over dts vs. driver-table when the
> type-c driver was introduced, but I either missed it or wasn't firm enough
> back then ;-) .
>
> Hence the "we'll need to live with it" for the type-c phy, but should not
> do similar things in future drivers.

So I guess now we're just waiting for some agreement from Kishon that
he's willing to land the PHY change? Heiko: presumably you could
apply the DP change to drm-misc? ...or is there some other process
needed there?

-Doug