linux-kernel - Re: [PATCH 1/2] clk: qcom: gcc-sm6350: Add missing parent

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Message-Id: <D6GGBPC4V5XV.YU8Z2KASBH07@fairphone.com>
Date: Fri, 20 Dec 2024 11:21:54 +0100
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Konrad Dybcio" <konrad.dybcio@....qualcomm.com>, "Bjorn Andersson"
 <andersson@...nel.org>, "Michael Turquette" <mturquette@...libre.com>,
 "Stephen Boyd" <sboyd@...nel.org>, "AngeloGioacchino Del Regno"
 <angelogioacchino.delregno@...ainline.org>, "Konrad Dybcio"
 <konradybcio@...nel.org>
Cc: <~postmarketos/upstreaming@...ts.sr.ht>, <phone-devel@...r.kernel.org>,
 <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] clk: qcom: gcc-sm6350: Add missing parent_map for
 two clocks

On Fri Dec 20, 2024 at 10:42 AM CET, Konrad Dybcio wrote:
> On 20.12.2024 10:03 AM, Luca Weiss wrote:
> > If a clk_rcg2 has a parent, it should also have parent_map defined,
>
>                       ^
>                         freq_tbl

I was basing this on that part of the clk-rcg2.c, so for every parent
there also needs to be a parent_map specified.

    int num_parents = clk_hw_get_num_parents(hw);
    [...]
    for (i = 0; i < num_parents; i++)
        if (cfg == rcg->parent_map[i].cfg)
            [...]

Should I still change the commit message? I guess there's no clk_rcg2
without a parent at all?

I guess I could reword it like that also or something?

  A clk_rcg2 needs to have a parent_map entry for every parent it has,
  otherwise [...]

Regards
Luca

>
> > otherwise we'll get a NULL pointer dereference when calling clk_set_rate
> > like the following:
> > 
> >   [    3.388105] Call trace:
> >   [    3.390664]  qcom_find_src_index+0x3c/0x70 (P)
> >   [    3.395301]  qcom_find_src_index+0x1c/0x70 (L)
> >   [    3.399934]  _freq_tbl_determine_rate+0x48/0x100
> >   [    3.404753]  clk_rcg2_determine_rate+0x1c/0x28
> >   [    3.409387]  clk_core_determine_round_nolock+0x58/0xe4
> >   [    3.421414]  clk_core_round_rate_nolock+0x48/0xfc
> >   [    3.432974]  clk_core_round_rate_nolock+0xd0/0xfc
> >   [    3.444483]  clk_core_set_rate_nolock+0x8c/0x300
> >   [    3.455886]  clk_set_rate+0x38/0x14c
> > 
> > Add the parent_map property for two clocks where it's missing and also
> > un-inline the parent_data as well to keep the matching parent_map and
> > parent_data together.
>
> The patch looks good otherwise
>
> Konrad