linux-kernel - Re: [PATCH v2 4/8] phy: rockchip-usb: expose the phy-internal PLLs

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Date:	Mon, 9 Nov 2015 13:12:44 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Heiko Stuebner <heiko@...ech.de>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Romain Perier <romain.perier@...il.com>,
	Arnd Bergmann <arnd@...db.de>, Lin Huang <hl@...k-chips.com>
Subject: Re: [PATCH v2 4/8] phy: rockchip-usb: expose the phy-internal PLLs

Heiko,

On Mon, Nov 9, 2015 at 1:08 PM, Heiko Stuebner <heiko@...ech.de> wrote:
> Hi Doug,
>
> Am Montag, 9. November 2015, 12:59:58 schrieb Doug Anderson:
>> On Sun, Nov 8, 2015 at 8:04 AM, Heiko Stuebner <heiko@...ech.de> wrote:
>> > +static const struct rockchip_usb_phy_pdata rk3066a_pdata = {
>> > +       .phys = (struct rockchip_usb_phys[]){
>> > +               { .reg = 0x17c, .pll_name = "sclk_otgphy0_480m" },
>> > +               { .reg = 0x188, .pll_name = "sclk_otgphy1_480m" },
>> > +               { /* sentinel */ }
>> > +       },
>> > +};
>> > +
>> > +static const struct rockchip_usb_phy_pdata rk3188_pdata = {
>> > +       .phys = (struct rockchip_usb_phys[]){
>> > +               { .reg = 0x10c, .pll_name = "sclk_otgphy0_480m" },
>> > +               { .reg = 0x11c, .pll_name = "sclk_otgphy1_480m" },
>> > +               { /* sentinel */ }
>> > +       },
>> > +};
>> > +
>> > +static const struct rockchip_usb_phy_pdata rk3288_pdata = {
>> > +       .phys = (struct rockchip_usb_phys[]){
>> > +               { .reg = 0x320, .pll_name = "sclk_otgphy0_480m" },
>> > +               { .reg = 0x334, .pll_name = "sclk_otgphy1_480m" },
>> > +               { .reg = 0x348, .pll_name = "sclk_otgphy2_480m" },
>> > +               { /* sentinel */ }
>> > +       },
>>
>> Slighly annoying to have to add a table for each SoC.  I'd imagine
>> this growing quite large.
>>
>> Would it be possible to query our parent clock name and then append a
>> "_480m" suffix?  Then you can magically get the name you want, right?
>> That doesn't preclude you from later overriding this or adding a "dts"
>> property for it, but it means no tables for now and (hopefully) for
>> the forseeable future.  ...and you get to kill a bunch of code in this
>> patch...
>>
>> You could fall back to some generic name based on the PHY device tree
>> node name if you wanted, or use the ID allocator...
>>
>>
>> Otherwise, this all looks good to me.  If you have a good reason why
>> using the parent name isn't a good idea, let me know and I can add my
>> Reviewed-by on this patch.
>
> Adding a _480m suffix was my initial solution. But the phy-supply clock
> is actually optional in the binding, so it may not be specified at all.
> Still the code needs this pll to work at all after the change, and
> inventing some completely random clock name seemed very strange
> (like pll_usbphy_REG or something) - especially as this would never
> have worked with the downstream clocks. As it is now, the downstream
> clock-tree will work indepent of the supply clock being specified.
>
> Also Rockchip seems to have moved to a different phy-ip, with one
> supplying clock, one pll and everything more tightly coupled,
> so we're probably getting a new driver for it, instead of additional
> entries for the picophy.

OK, seems quite reasonable to me.

Reviewed-by: Douglas Anderson <dianders@...omium.org>
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