linux-kernel - Re: [PATCH v5 2/2] phy: rockchip-inno-usb2: add a new driver for Rockchip usb2phy

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Date:	Wed, 29 Jun 2016 16:27:19 +0200
From:	Heiko Stuebner <heiko@...ech.de>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Frank Wang <frank.wang@...k-chips.com>, dianders@...omium.org,
	linux@...ck-us.net, groeck@...omium.org, jwerner@...omium.org,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	xzy.xu@...k-chips.com, kever.yang@...k-chips.com,
	huangtao@...k-chips.com, william.wu@...k-chips.com
Subject: Re: [PATCH v5 2/2] phy: rockchip-inno-usb2: add a new driver for Rockchip usb2phy

Hi Kishon,

Am Mittwoch, 29. Juni 2016, 19:44:52 schrieb Kishon Vijay Abraham I:
> On Friday 17 June 2016 10:16 PM, Heiko Stübner wrote:
> > Am Freitag, 17. Juni 2016, 17:24:46 schrieb Kishon Vijay Abraham I:
> > [...]
> > 
> >>> +	/* find out a proper config which can be matched with dt. */
> >>> +	index = 0;
> >>> +	while (phy_cfgs[index].reg) {
> >>> +		if (phy_cfgs[index].reg == reg) {
> >> 
> >> Why not pass these config values from dt? Moreover finding the config
> >> using register offset is bound to break.
> > 
> > As you have probably seen, this phy block is no stand-alone
> > (mmio-)device, but gets controlled through special register/bits in the
> > so called "General Register Files" syscon.
> > 
> > The values stored and accessed here, are the location and layout of
> > those
> > control registers. Bits in those phy control registers at times move
> > between phy-versions in different socs (rk3036, rk3228, rk3366, rk3368,
> > rk3399) and some are even missing. So I don't really see a nice way to
> > describe that in dt without describing the register and offset of each
> > of those 22 used bits individually.
> > 
> > 
> > I'm also not sure where you expect it to break? The reg-offset is the
> > offset of the phy inside the GRF and the Designware-phy also already
> > does something similar to select some appropriate values.
> 
> I'm concerned the phy can be placed in the different reg-offset within GRF
> (like in the next silicon revision) and this driver can't be used.

That is something that has not happened with all Rockchip SoCs I have had in 
my hands so far.

While the GRF is some sort-of wild-west area with settings for vastly 
different blocks in there and always changes between different socs (rk3288 
[4-core A17] <-> rk3366 <-> rk3368 [8-core A53] <-> rk3399 etc) there 
haven't been such changes (different register offsets) between soc-revisions 
of the same soc that I know off.

The GRF also includes such important things like the whole pinctrl handling, 
so if there were such offset changes in the GRF a lot of drivers (and 
maintainers) would get very unhappy - me included :-) .


Heiko