linux-kernel - Re: [PATCH] clk: starfive: jh7100: Use provided clocks instead of hardcoded names

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Date: Thu, 14 Mar 2024 09:56:54 -0500
From: Samuel Holland <samuel.holland@...ive.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Albert Ou <aou@...s.berkeley.edu>, linux-clk@...r.kernel.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Emil Renner Berthing <kernel@...il.dk>, Hal Feng
 <hal.feng@...rfivetech.com>, Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Conor Dooley <conor.dooley@...rochip.com>,
 Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH] clk: starfive: jh7100: Use provided clocks instead of
 hardcoded names

Hi Geert,

On 2024-03-14 9:48 AM, Geert Uytterhoeven wrote:
> On Thu, Mar 14, 2024 at 3:32 PM Samuel Holland
> <samuel.holland@...ive.com> wrote:
>> On 2024-03-14 6:05 AM, Geert Uytterhoeven wrote:
>>> The Starfive JH7100 clock driver does not use the DT "clocks" property
>>> to find its external input clocks, but instead relies on the names of
>>> the actual external clock providers.  This is fragile, and caused
>>> breakage when sanitizing clock names in DT.
>>>
>>> Fix this by obtaining the external input clocks through the DT "clocks"
>>> property, and using their clk_hw objects or corresponding name.
>>>
>>> Fixes: f03606470886 ("riscv: dts: starfive: replace underscores in node names")
>>> Fixes: 4210be668a09ee20 ("clk: starfive: Add JH7100 clock generator driver")
>>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> 
>>> --- a/drivers/clk/starfive/clk-starfive-jh7100.c
>>> +++ b/drivers/clk/starfive/clk-starfive-jh7100.c
> 
>>> @@ -298,13 +311,23 @@ static int __init clk_starfive_jh7100_probe(struct platform_device *pdev)
>>>       if (IS_ERR(priv->base))
>>>               return PTR_ERR(priv->base);
>>>
>>> +     for (idx = 0; idx < EXT_NUM_CLKS; idx++) {
>>> +             clk = devm_clk_get(&pdev->dev, jh7100_ext_clk[idx]);
>>> +             if (IS_ERR(clk))
>>> +                     return PTR_ERR(clk);
>>> +
>>> +             priv->ext[idx] = __clk_get_hw(clk);
>>> +     }
>>> +
>>> +     osc_sys = clk_hw_get_name(priv->ext[EXT_CLK_OSC_SYS]);
>>> +
>>>       priv->pll[0] = devm_clk_hw_register_fixed_factor(priv->dev, "pll0_out",
>>> -                                                      "osc_sys", 0, 40, 1);
>>> +                                                      osc_sys, 0, 40, 1);
>>>       if (IS_ERR(priv->pll[0]))
>>>               return PTR_ERR(priv->pll[0]);
>>>
>>>       priv->pll[1] = devm_clk_hw_register_fixed_factor(priv->dev, "pll1_out",
>>> -                                                      "osc_sys", 0, 64, 1);
>>> +                                                      osc_sys, 0, 64, 1);
>>
>> These should use devm_clk_hw_register_fixed_factor_parent_hw(). (Or you could
> 
> Thanks, I didn't know about that function!
> 
>> define a devm_clk_hw_register_fixed_factor_fw_name() and drop the other changes.)
> 
> Sorry, I don't understand what you mean here?

In the loop below, the parents are already referenced via .fw_name. That means
the string is the DT clock-names property value, not the Linux-internal clock
name (see clk_core_get()). These two function calls are the only ones that
depend on the internal clock name. If you change them to use .fw_name as well,
the clk_core_get() will do the right thing, and you don't need to manually call
devm_clk_get().

Regards,
Samuel