RE: [PATCH v2 2/3] clk: xilinx: vcu: don't set pll_ref as parent of VCU(enc/dec) clocks

[Visavalia, Rohit]

Hi @Geert Uytterhoeven, @Stephen Boyd <sboyd@xxxxxxxxxx> 

>-----Original Message-----
>From: Visavalia, Rohit
>Sent: Monday, January 6, 2025 3:34 PM
>To: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>Cc: mturquette@xxxxxxxxxxxx; sboyd@xxxxxxxxxx; Simek, Michal
><michal.simek@xxxxxxx>; Sagar, Vishal <vishal.sagar@xxxxxxx>;
>javier.carrasco.cruz@xxxxxxxxx; geert+renesas@xxxxxxxxx; u.kleine-
>koenig@xxxxxxxxxxxx; linux-clk@xxxxxxxxxxxxxxx; linux-arm-
>kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
>Subject: RE: [PATCH v2 2/3] clk: xilinx: vcu: don't set pll_ref as parent of
>VCU(enc/dec) clocks
>
>Hi Geert,
>
>Thank for the review.
>
>>-----Original Message-----
>>From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>>Sent: Friday, January 3, 2025 12:58 AM
>>To: Visavalia, Rohit <rohit.visavalia@xxxxxxx>
>>Cc: mturquette@xxxxxxxxxxxx; sboyd@xxxxxxxxxx; Simek, Michal
>><michal.simek@xxxxxxx>; Sagar, Vishal <vishal.sagar@xxxxxxx>;
>>javier.carrasco.cruz@xxxxxxxxx; geert+renesas@xxxxxxxxx; u.kleine-
>>koenig@xxxxxxxxxxxx; linux-clk@xxxxxxxxxxxxxxx; linux-arm-
>>kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
>>Subject: Re: [PATCH v2 2/3] clk: xilinx: vcu: don't set pll_ref as
>>parent of
>>VCU(enc/dec) clocks
>>
>>Hi Rohit,
>>
>>On Thu, Jan 2, 2025 at 6:04 PM Rohit Visavalia <rohit.visavalia@xxxxxxx> wrote:
>>> CCF will try to adjust parent clock to set desire clock frequency of
>>> child clock. So if pll_ref is not a fixed-clock then while setting
>>> rate of enc/dec clocks pll_ref may get change, which may make VCU
>>malfunction.
>>>
>>> Signed-off-by: Rohit Visavalia <rohit.visavalia@xxxxxxx>
>>> ---
>>> Changes in v2:
>>>   - none
>>>   - Link to v1:
>>> https://lore.kernel.org/linux-clk/20241226122023.3439559-3-rohit.visa
>>> v
>>> alia@xxxxxxx
>>> ---
>>>  drivers/clk/xilinx/xlnx_vcu.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/clk/xilinx/xlnx_vcu.c
>>> b/drivers/clk/xilinx/xlnx_vcu.c index 88b3fd8250c2..c520ae1ba65e
>>> 100644
>>> --- a/drivers/clk/xilinx/xlnx_vcu.c
>>> +++ b/drivers/clk/xilinx/xlnx_vcu.c
>>> @@ -547,7 +547,7 @@ static int xvcu_register_clock_provider(struct
>>xvcu_device *xvcu)
>>>                 return PTR_ERR(hw);
>>>         xvcu->pll_post = hw;
>>>
>>> -       parent_data[0].fw_name = "pll_ref";
>>> +       parent_data[0].fw_name = "dummy_name";
>>>         parent_data[1].hw = xvcu->pll_post;
>>>
>>>         hws[CLK_XVCU_ENC_CORE] =
>>
>>You completely ignored Stephen's comment, which suggests to not pas
>>CLK_SET_RATE_PARENT instead (see xvcu_clk_hw_register_leaf()).
>
>Thanks for pointing this out. Let me take care this in v3 patch series.

We can drop this patch[PATCH v2 2/3], as original issue was occurring when "pll_ref" clock is being changed to get the best desire clock rate for encoder and decoder. And now with recent changes in Xilinx clock driver(https://github.com/torvalds/linux/commit/b782921ddd7f84f524723090377903f399fdbbcb & https://github.com/torvalds/linux/commit/1fe15be1fb613534ecbac5f8c3f8744f757d237d) encoder and decoder are getting parent as "pll_post" to get best desire clock rate and not changing rate of "pll_ref".

Thanks
Rohit
>
>>
>>Gr{oetje,eeting}s,
>>
>>                        Geert
>>
>>--
>>Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
>>geert@xxxxxxxxxxxxxx
>>
>>In personal conversations with technical people, I call myself a
>>hacker. But when I'm talking to journalists I just say "programmer" or something
>like that.
>>                                -- Linus Torvalds
>
>Thanks
>Rohit