linux-kernel - Re: [PATCH v2] clk: ti: dra7-atl: don't allocate `parent

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Message-ID: <CABGWkvp1iMN-4XDN_ifg6uyvQbpRzNyat_eDziWY75Cf_hCpQw@mail.gmail.com>
Date:   Sun, 30 Oct 2022 14:00:46 +0100
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        michael@...rulasolutions.com, kernel test robot <lkp@...el.com>,
        Allison Randal <allison@...utok.net>,
        Miaoqian Lin <linmq006@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Tero Kristo <kristo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Lindgren <tony@...mide.com>, linux-clk@...r.kernel.org,
        linux-omap@...r.kernel.org
Subject: Re: [PATCH v2] clk: ti: dra7-atl: don't allocate `parent_names' variable

Hi Stephen,

On Fri, Oct 28, 2022 at 2:27 AM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Dario Binacchi (2022-10-18 09:03:52)
> > diff --git a/drivers/clk/ti/clk-dra7-atl.c b/drivers/clk/ti/clk-dra7-atl.c
> > index ff4d6a951681..78482d1a4a33 100644
> > --- a/drivers/clk/ti/clk-dra7-atl.c
> > +++ b/drivers/clk/ti/clk-dra7-atl.c
> > @@ -188,24 +188,17 @@ static void __init of_dra7_atl_clock_setup(struct device_node *node)
> >                 goto cleanup;
> >         }
> >
> > -       parent_names = kzalloc(sizeof(char *), GFP_KERNEL);
> > -
> > -       if (!parent_names)
> > -               goto cleanup;
> > -
> >         parent_names[0] = of_clk_get_parent_name(node, 0);
>
> Can you use struct clk_parent_data instead and assign index to 0? Then
> we don't even need to use of_clk_get_parent_name() here.

I tried to test your suggestions on another platform (I don't have the
hw to test the driver change) but if I
don't add pdata.name = of_clk_get_parent_name () the board boot up fails.

As far I can see from the clk_core_populate_parent_map()

....
/* Copy everything over because it might be __initdata */
for (i = 0, parent = parents; i < num_parents; i++, parent++) {
    parent->index = -1;
    if (parent_names) {
        /* throw a WARN if any entries are NULL */
       WARN(!parent_names[i],
            "%s: invalid NULL in %s's .parent_names\n",
            __func__, core->name);
        ret = clk_cpy_name(&parent->name, parent_names[i],
                                        true);
    } else if (parent_data) {
        parent->hw = parent_data[i].hw;
        parent->index = parent_data[i].index;
        ret = clk_cpy_name(&parent->fw_name,
                                         parent_data[i].fw_name, false);
        if (!ret)
            ret = clk_cpy_name(&parent->name,
                                            parent_data[i].name,
                                            false);
...


The function clk_cpy_name() is called with the parameter "mus_exist"
to true in the path "parent_names" and false
in the path "parent_data". Therefore, in the path "parent_data" it is
allowed that parent-> name is not set.
In doing so, therefore, the change would not even be backward compatible.

So, IMHO, there are 2 possible options:
 1 okay to use parent_data, but we keep using of_clk_get_parent_name
() to set parent_data::name.
 2 okay to use the version v2 of the patch.

What do you think?

Thanks and regards,
Dario

-- 

Dario Binacchi

Embedded Linux Developer

dario.binacchi@...rulasolutions.com

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