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

From: Heiko Stuebner <heiko@sntech.de>
To: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Frank Wang <frank.wang@rock-chips.com>,
	dianders@chromium.org, linux@roeck-us.net, groeck@chromium.org,
	jwerner@chromium.org, robh+dt@kernel.org, pawel.moll@arm.com,
	mark.rutland@arm.com, ijc+devicetree@hellion.org.uk,
	galak@codeaurora.org, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org, linux-usb@vger.kernel.org,
	linux-rockchip@lists.infradead.org, xzy.xu@rock-chips.com,
	kever.yang@rock-chips.com, huangtao@rock-chips.com,
	william.wu@rock-chips.com
Subject: Re: [PATCH v5 2/2] phy: rockchip-inno-usb2: add a new driver for Rockchip usb2phy
Date: Wed, 29 Jun 2016 16:27:19 +0200	[thread overview]
Message-ID: <2624359.mbyKrcyvqy@phil> (raw)
In-Reply-To: <5773D7DC.9050902@ti.com>

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