linux-kernel - Re: [PATCH v3 4/6] clk: meson: t7: add support for the T7 SoC PLL clock

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Message-ID: <1jh60fd52u.fsf@starbuckisacylon.baylibre.com>
Date: Mon, 16 Jun 2025 18:27:53 +0200
From: Jerome Brunet <jbrunet@...libre.com>
To: Jian Hu <jian.hu@...ogic.com>
Cc: Xianwei Zhao <xianwei.zhao@...ogic.com>,  Chuan Liu
 <chuan.liu@...ogic.com>,  Neil Armstrong <neil.armstrong@...aro.org>,
  Kevin Hilman <khilman@...libre.com>,  Stephen Boyd <sboyd@...nel.org>,
  Michael Turquette <mturquette@...libre.com>,  Dmitry Rokosov
 <ddrokosov@...rdevices.ru>,  robh+dt <robh+dt@...nel.org>,  Rob Herring
 <robh@...nel.org>,  devicetree <devicetree@...r.kernel.org>,  linux-clk
 <linux-clk@...r.kernel.org>,  linux-amlogic
 <linux-amlogic@...ts.infradead.org>,  linux-kernel
 <linux-kernel@...r.kernel.org>,  linux-arm-kernel
 <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 4/6] clk: meson: t7: add support for the T7 SoC PLL
 clock

On Thu 12 Jun 2025 at 21:02, Jian Hu <jian.hu@...ogic.com> wrote:

>>> +
>>> +static struct clk_regmap t7_pcie_pll_od = {
>>> +     .data = &(struct clk_regmap_div_data){
>>> +             .offset = ANACTRL_PCIEPLL_CTRL0,
>>> +             .shift = 16,
>>> +             .width = 5,
>>> +             .flags = CLK_DIVIDER_ONE_BASED |
>>> +                      CLK_DIVIDER_ALLOW_ZERO,
>> What's the behaviour of the divider on zero then ?
>
>
> If there is no CLK_DIVDER_ALLOW_ZERO, there is a warning when registering
> t7_pcie_pll_od.
>
> like this:
>
>   ------------[ cut here ]------------
>   WARNING: CPU: 1 PID: 1 at drivers/clk/clk-divider.c:140
> divider_recalc_rate+0xfc/0x100
>   pcie_pll_od: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set
>   Modules linked in:
>  CPU: 1 PID: 1 Comm: swapper/0 Not tainted
> 5.4.283-09976-ga803e94eed88-dirty #91
>   Hardware name: tm2_t962e2_ab311 (DT)
>  Call trace:
>   [ffffffc020003750+  64][<ffffffc0100e3e3c>] dump_backtrace+0x0/0x1e4
>   [ffffffc020003790+  32][<ffffffc0100e4044>] show_stack+0x24/0x34
>   [ffffffc0200037b0+  96][<ffffffc01130a2e8>] dump_stack+0xbc/0x108
>  [ffffffc020003810+ 144][<ffffffc01010c484>] __warn+0xf4/0x1b8
>   [ffffffc0200038a0+  64][<ffffffc01010c5f4>] warn_slowpath_fmt+0xac/0xc8
>  [ffffffc0200038e0+  64][<ffffffc01061d364>] divider_recalc_rate+0xfc/0x100
>  [ffffffc020003920+  80][<ffffffc010624e84>]
> clk_regmap_div_recalc_rate+0x74/0x88
>   [ffffffc020003970+  96][<ffffffc010616a54>] __clk_register+0x62c/0xb78
>
> so add it to avoid the warning.

That does not really answer my question