linux-kernel - Re: [PATCH v4 0/4] rockchip: add GATE

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Date:   Wed, 25 Oct 2023 14:40:30 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     conor+dt@...nel.org, heiko@...ech.de, kever.yang@...k-chips.com,
        krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
        robh+dt@...nel.org, zhangqing@...k-chips.com,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-kernel@...r.kernel.org, huangtao@...k-chips.com,
        andy.yan@...k-chips.com
Subject: Re: [PATCH v4 0/4] rockchip: add GATE_LINK

Quoting Sebastian Reichel (2023-10-25 12:48:49)
> Hello Stephen,
> 
> On Mon, Oct 23, 2023 at 06:47:17PM -0700, Stephen Boyd wrote:
> > Quoting Elaine Zhang (2023-10-18 00:01:40)
> > > Recent Rockchip SoCs have a new hardware block called Native Interface
> > > Unit (NIU), which gates clocks to devices behind them. These effectively
> > > need two parent clocks.
> > > Use GATE_LINK to handle this.
> > 
> > Why can't pm clks be used here? The qcom clk driver has been doing that
> > for some time now. 
> > 
> >  $ git grep pm_clk_add -- drivers/clk/qcom/
> 
> Maybe I'm mistaken, but as far as I can tell this is adding the
> dependency on controller level and only works because Qualcomm
> has multiple separate clock controllers. In the Rockchip design
> there is only one platform device.
> 
> Note, that the original downstream code from Rockchip actually used
> pm_clk infrastructure by moving these clocks to separate platform
> devices. I changed this when upstreaming the code, since that leaks
> into DT and from DT point of view there should be only one clock
> controller.
> 

Why can't the rockchip driver bind to a single device node and make
sub-devices for each clk domain and register clks for those? Maybe it
can use the auxiliary driver infrastructure to do that?