[PATCH v3 4/6] clk: meson: t7: add support for the T7 SoC PLL clock
Jian Hu
jian.hu at amlogic.com
Tue Jun 24 19:52:28 PDT 2025
On 2025/6/17 0:27, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
>
> On Thu 12 Jun 2025 at 21:02, Jian Hu <jian.hu at amlogic.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
Sorry, I did not get you before.
I have set OD to 0. And measure pcie frequency, It is 37.5Mhz.
4800Mhz/2/32/2=37.5Mhz, and the OD equal zero means divided by 32 in fact.
Here is the test result:
devm 0xfe008140 32
0xD40C04C8
cat /sys/kernel/debug/meson-clk-msr/measure_summary | grep pcie
[16] pcie_clk_inp 37500000 +/1 3125HZ
the OD divider is N crossover. it is one based.
and It's possible to go from 1 to 31 crossovers.
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