linux-kernel - Re: [PATCH v3] clk: sunxi-ng: sun50i: h6: Modify GPU clock configuration to support DFS

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Date:   Fri, 08 Jul 2022 18:15:27 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     samuel@...lland.org, Roman Stratiienko <r.stratiienko@...il.com>
Cc:     peron.clem@...il.com, mturquette@...libre.com, sboyd@...nel.org,
        mripard@...nel.org, wens@...e.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Roman Stratiienko <r.stratiienko@...il.com>
Subject: Re: [PATCH v3] clk: sunxi-ng: sun50i: h6: Modify GPU clock configuration to support DFS

Dne torek, 05. julij 2022 ob 09:52:26 CEST je Roman Stratiienko napisal(a):
> Using simple bash script it was discovered that not all CCU registers
> can be safely used for DFS, e.g.:
> 
>     while true
>     do
>         devmem 0x3001030 4 0xb0003e02
>         devmem 0x3001030 4 0xb0001e02
>     done
> 
> Script above changes the GPU_PLL multiplier register value. While the
> script is running, the user should interact with the user interface.
> 
> Using this method the following results were obtained:
> | Register  | Name           | Bits  | Values | Result |
> | --        | --             | --    | --     | --     |
> | 0x3001030 | GPU_PLL.MULT   | 15..8 | 20-62  | OK     |
> | 0x3001030 | GPU_PLL.INDIV  |     1 | 0-1    | OK     |
> | 0x3001030 | GPU_PLL.OUTDIV |     0 | 0-1    | FAIL   |
> | 0x3001670 | GPU_CLK.DIV    |  3..0 | ANY    | FAIL   |
> 
> DVFS started to work seamlessly once dividers which caused the
> glitches were set to fixed values.
> 
> Signed-off-by: Roman Stratiienko <r.stratiienko@...il.com>
> 

Applied, thanks!

Best regards,
Jernej