linux-kernel - Re: [PATCH 6/8] clk: tegra30: add 2d and 3d idle clocks

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Message-ID: <9acf4b987a6b34b596c5752de252de99@codethink.co.uk>
Date:   Mon, 23 Jul 2018 12:37:38 +0100
From:   Ben Dooks <ben.dooks@...ethink.co.uk>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     pdeschrijver@...dia.com, jonathanh@...dia.co,
        thierry.reding@...il.com, linux-clk@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        pgaikwad@...dia.com, linux-kernel@...ts.codethink.co.uk
Subject: Re: [PATCH 6/8] clk: tegra30: add 2d and 3d idle clocks



On 2018-07-23 12:33, Dmitry Osipenko wrote:
> On Monday, 23 July 2018 11:28:25 MSK Ben Dooks wrote:
>> On 2018-07-22 12:55, Dmitry Osipenko wrote:
>> > On Friday, 20 July 2018 16:45:30 MSK Ben Dooks wrote:
>> >> The 2D and 3D clocks have an IDLE field in bits 15:8 so add these
>> >> clocks by making a 2D and 3D mux, and split the divider into the
>> >> standard 2D/3D ones and 2D/3D idle clocks.
>> >>
>> >> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
>> 
>> [snip]
> 
>> @@ -658,8 +658,12 @@ static struct tegra_devclk devclks[] __initdata = 
>> {
>>  	{ .dev_id = "mpe", .dt_id = TEGRA30_CLK_MPE },
>>  	{ .dev_id = "host1x", .dt_id = TEGRA30_CLK_HOST1X },
>>  	{ .dev_id = "3d", .dt_id = TEGRA30_CLK_GR3D },
>> +	{ .dev_id = "3d", .con_id = "mux", .dt_id = TEGRA30_CLK_GR3D_MUX },
>> +	{ .dev_id = "3d", .con_id = "idle", .dt_id = TEGRA30_CLK_GR3D_IDLE 
>> },
>>  	{ .dev_id = "3d2", .dt_id = TEGRA30_CLK_GR3D2 },
> 
> The  "3d2" also has the "idle" divisor, why have you skipped it?

Thanks, missed this.

>>  	{ .dev_id = "2d", .dt_id = TEGRA30_CLK_GR2D },
>> +	{ .dev_id = "2d", .con_id = "mux", .dt_id = TEGRA30_CLK_GR2D_MUX },
>> +	{ .dev_id = "2d", .con_id = "idle", .dt_id = TEGRA30_CLK_GR2D_IDLE 
>> },
>>  	{ .dev_id = "se", .dt_id = TEGRA30_CLK_SE },
>>  	{ .dev_id = "mselect", .dt_id = TEGRA30_CLK_MSELECT },
>>  	{ .dev_id = "tegra-nor", .dt_id = TEGRA30_CLK_NOR },
> 
> [snip]
> 
>> 
>> > According to TRM, Tegra20 and Tegra114 have these "idle-mode" clock
>> > dividers
>> > as well. Why only T30 should have them?
>> 
>> I've got a separate series to sort t20 bits out, i've not used the
>> tegra114
>> 
> 
> This makes this series to look a bit inconsistent, please send out all 
> the
> patches to give a consistent view.
> 
> I don't see anything that could really stop you from adding the clocks 
> for
> T114, its 2d/3d clocks definition pretty matches to T20/30.

I'd prefer not to be touch architectures I don't have access to do.

> >> a/include/dt-bindings/clock/tegra30-car.h
>> >> b/include/dt-bindings/clock/tegra30-car.h index
>> >> 3c90f1535551..eda4ca60351e
>> >> 100644
>> >> --- a/include/dt-bindings/clock/tegra30-car.h
>> >> +++ b/include/dt-bindings/clock/tegra30-car.h
>> >> @@ -269,6 +269,11 @@
>> >>
>> >>  #define TEGRA30_CLK_AUDIO3_MUX 306
>> >>  #define TEGRA30_CLK_AUDIO4_MUX 307
>> >>  #define TEGRA30_CLK_SPDIF_MUX 308
>> >>
>> >> -#define TEGRA30_CLK_CLK_MAX 309
>> >> +
>> >> +#define TEGRA30_CLK_GR2D_MUX	309
>> >> +#define TEGRA30_CLK_GR3D_MUX	310
>> >> +#define TEGRA30_CLK_GR2D_IDLE	311
>> >> +#define TEGRA30_CLK_GR3D_IDLE	312
>> >> +#define TEGRA30_CLK_CLK_MAX 313
>> >>
>> >>  #endif	/* _DT_BINDINGS_CLOCK_TEGRA30_CAR_H */
>> >
>> > IIUC, that "idle-mode" divisor is just some kind of power-safe feature,
>> > is
>> > there any real use-case for these clocks? Why not to just pre-configure
>> > the
>> > "idle-mode" bits during the clocks initialization?
>> 
>> It is is nice to have it available after to check,
> 
> Please initialize the "idle" clock rate via the tegra_clk_init_table in 
> the
> patch that adds the clock or in a followup patch within the same 
> patchset.
> 
>> other than that we're
>> not
>> using any drivers that currently dynamically change the values of 
>> this.
> 
> All changes made to upstream kernel must be justified, the only 
> acceptable
> justification is that a change is required for the upstream driver.