linux-kernel - Re: [PATCH] clk: qcom: gcc-sdm660: Replace usage of parent

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Date:   Tue, 24 Aug 2021 15:38:53 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        angelogioacchino.delregno@...ainline.org
Subject: Re: [PATCH] clk: qcom: gcc-sdm660: Replace usage of parent_names

On Tue 24 Aug 13:46 PDT 2021, Marijn Suijten wrote:

> Hi Bjorn,
> 
> Thanks for this cleanup, that's needed and much appreciated!
> 
> On 8/24/21 5:06 PM, Bjorn Andersson wrote:
> > Using parent_data and parent_hws, instead of parent_names, does protect
> > against some cases of incompletely defined clock trees. While it turns
> > out that the bug being chased this time was totally unrelated, this
> > patch converts the SDM660 GCC driver to avoid such issues.
> > 
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> 
> 
> Tested-by: Marijn Suijten <marijn.suijten@...ainline.org>
> 
> On the Sony Xperia XA2 Ultra, bar the necessary change in the 14NM DSI PHY
> driver commented below.
> 
> > [..]
> > -
> > -static struct clk_fixed_factor xo = {
> > -	.mult = 1,
> > -	.div = 1,
> > -	.hw.init = &(struct clk_init_data){
> > -		.name = "xo",
> > -		.parent_names = (const char *[]){ "xo_board" },
> > -		.num_parents = 1,
> > -		.ops = &clk_fixed_factor_ops,
> > -	},
> > -};
> 
> 
> Removing the global "xo" clock makes it so that our 14nm DSI PHY does not
> have a parent clock anymore, as the clock is called "xo_board" nowadays
> ("xo" in the position of fw_name is, as you know, only local to this driver
> because it is named that way in the clock-names property). We (SoMainline)
> suffer the same DSI PHY hardcoding issue on many other boards and are at
> this point investigating whether to provide &xo_board in DT like any other
> sane driver.  Do you happen to know if work is already underway to tackle
> this?
> 

As far as I can tell most other platforms doesn't define "xo" either.
E.g. according to debugfs dsi0vco_clk doesn't have a parent on sdm845...

Sounds like we should update the dsi phys to specify a fw_name and
update binding and dts to provide this...


Does this cause a noticeable regression or it's just that we have a
dangling clock?

> >   static struct clk_alpha_pll gpll0_early = {
> >   	.offset = 0x0,
> >   	.regs = clk_alpha_pll_regs[CLK_ALPHA_PLL_TYPE_DEFAULT],
> > @@ -158,7 +35,9 @@ static struct clk_alpha_pll gpll0_early = {
> >   		.enable_mask = BIT(0),
> >   		.hw.init = &(struct clk_init_data){
> >   			.name = "gpll0_early",
> > -			.parent_names = (const char *[]){ "xo" },
> > +			.parent_data = &(const struct clk_parent_data){
> > +				.fw_name = "xo",
> > +			},
> 
> 
> I wish we could use .parent_names for a list of .fw_name's too

Afaict specifying "name" in struct clk_parent_data is the same as using
parent_names. But I'm not up to speed on the details of how to migrate
the dsi phys.

> > [..]
> > @@ -265,7 +270,7 @@ static struct clk_rcg2 blsp1_qup1_i2c_apps_clk_src = {
> >   	.freq_tbl = ftbl_blsp1_qup1_i2c_apps_clk_src,
> >   	.clkr.hw.init = &(struct clk_init_data){
> >   		.name = "blsp1_qup1_i2c_apps_clk_src",
> > -		.parent_names = gcc_parent_names_xo_gpll0_gpll0_early_div,
> > +		.parent_data = gcc_parent_data_xo_gpll0_gpll0_early_div,
> >   		.num_parents = 3,
> 
> 
> How about using ARRAY_SIZE(gcc_parent_data_xo_gpll0_gpll0_early_div) now?
> Same for every other occurrence of this pattern.
> 

I omitted that because it felt unrelated to the change I was doing, but
it could certainly be done.

Regards,
Bjorn