linux-kernel - Re: [PATCH v2 2/4] hwrng: stm32 - implement support for STM32MP25x platforms

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Message-ID: <dca83197-3484-4d6b-8507-118bf9e80e19@denx.de>
Date: Mon, 14 Oct 2024 20:55:05 +0200
From: Marek Vasut <marex@...x.de>
To: Gatien CHEVALLIER <gatien.chevallier@...s.st.com>,
 Olivia Mackall <olivia@...enic.com>, Herbert Xu
 <herbert@...dor.apana.org.au>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Lionel Debieve <lionel.debieve@...s.st.com>
Cc: linux-crypto@...r.kernel.org, devicetree@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] hwrng: stm32 - implement support for STM32MP25x
 platforms

On 10/14/24 2:36 PM, Gatien CHEVALLIER wrote:
> 
> 
> On 10/14/24 10:52, Marek Vasut wrote:
>> On 10/14/24 10:38 AM, Gatien CHEVALLIER wrote:
>>>
>>>
>>> On 10/11/24 18:17, Marek Vasut wrote:
>>>> On 10/11/24 5:41 PM, Gatien Chevallier wrote:
>>>>
>>>> [...]
>>>>
>>>>> @@ -551,6 +565,41 @@ static int stm32_rng_probe(struct 
>>>>> platform_device *ofdev)
>>>>>       priv->rng.read = stm32_rng_read;
>>>>>       priv->rng.quality = 900;
>>>>> +    if (!priv->data->nb_clock || priv->data->nb_clock > 2)
>>>>> +        return -EINVAL;
>>>>> +
>>>>> +    priv->clk_bulk = devm_kzalloc(dev, priv->data->nb_clock * 
>>>>> sizeof(*priv->clk_bulk),
>>>>> +                      GFP_KERNEL);
>>>>> +    if (!priv->clk_bulk)
>>>>> +        return -ENOMEM;
>>>>
>>>> Try this:
>>>>
>>>> ret = devm_clk_bulk_get(dev, priv->data->nb_clock, priv->clk_bulk);
>>>> ...
>>>> // Swap the clock if they are not in the right order:
>>>> if (priv->data->nb_clock == 2 &&
>>>>      strcmp(__clk_get_name(priv->clk_bulk[0].clk), "core"))
>>>> {
>>>>   const char *id = priv->clk_bulk[1].id;
>>>>   struct clk *clk = priv->clk_bulk[1].clk;
>>>>   priv->clk_bulk[1].id = priv->clk_bulk[0].id;
>>>>   priv->clk_bulk[1].clk = priv->clk_bulk[0].clk;
>>>>   priv->clk_bulk[0].id = id;
>>>>   priv->clk_bulk[0].clk = clk;
>>>> }
>>>>
>>>
>>> Hi Marek,
>>>
>>> This won't work as the name returned by this API is clk->core->name.
>>> AFAICT, it doesn't correspond to the names present in the device tree
>>> under the "clock-names" property.
>>> Any other idea or are you fine with what's below?
>> Hmmm, it is not great, but at least it reduces the changes throughout 
>> the driver, so that is an improvement.
>>
>> I guess one could do some of_clk_get() and clk_is_match() in probe to 
>> look up the clock in OF by name and then compare which clock is which 
>> before swapping them in clk_bulk[] array, but that might be too 
>> convoluted?
> 
> Yes, probably too much. What's present in the patch is not close to
> perfection but has the advantage of being straightforward. If we agree
> on that, I'll send a V3 containing the modifications in the bindings
> file.
Errr, I'm sorry, maybe there is a way to do this better. Look at 
drivers/clk/clk-bulk.c :

  15 static int __must_check of_clk_bulk_get(struct device_node *np, int 
num_clks,
  16                                         struct clk_bulk_data *clks)
  17 {
  18         int ret;
  19         int i;
  20
  21         for (i = 0; i < num_clks; i++) {
  22                 clks[i].id = NULL;
  23                 clks[i].clk = NULL;
  24         }
  25
  26         for (i = 0; i < num_clks; i++) {
  27                 of_property_read_string_index(np, "clock-names", i, 
&clks[i].id);
  28                 clks[i].clk = of_clk_get(np, i);

If I read this right, then clks[i].id should be the DT clock name. So 
the swap conditional above could use .id to identify whether the first 
position is core clock or not, like this:

if (priv->data->nb_clock == 2 &&
     strcmp(__clk_get_name(priv->clk_bulk[0].id), "core"))
                                             ^^

You might need to use devm_clk_bulk_get_all() to access the 
of_clk_bulk_get() .

Or am I missing something still ?