From: Sean Anderson <seanga2@gmail.com>
To: Damien Le Moal <Damien.LeMoal@wdc.com>,
Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
"palmer@dabbelt.com" <palmer@dabbelt.com>,
"sboyd@kernel.org" <sboyd@kernel.org>,
"linus.walleij@linaro.org" <linus.walleij@linaro.org>,
"p.zabel@pengutronix.de" <p.zabel@pengutronix.de>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>
Subject: Re: [PATCH v4 11/21] riscv: Add Canaan Kendryte K210 clock driver
Date: Mon, 7 Dec 2020 17:58:00 -0500 [thread overview]
Message-ID: <f6b54c11-adf8-328e-e1d5-c759ac5ee2e2@gmail.com> (raw)
In-Reply-To: <CH2PR04MB65224960F89E4EB1CE253743E7CE0@CH2PR04MB6522.namprd04.prod.outlook.com>
On 12/7/20 5:14 AM, Damien Le Moal wrote:
> On 2020/12/07 19:06, Geert Uytterhoeven wrote:
>> Hi Damien,
>>
>> On Mon, Dec 7, 2020 at 10:55 AM Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
>>> On 2020/12/07 17:44, Geert Uytterhoeven wrote:
>>>> On Mon, Dec 7, 2020 at 4:52 AM Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
>>>>> I prepared a v5 series addressing your comments (and other comments).
>>>>> I will post that later today after some more tests.
>>>>
>>>> Thanks, already looking at k210-sysctl-v18...
>>>>
>>>>> On Fri, 2020-12-04 at 22:19 -0800, Stephen Boyd wrote:
>>>>>>> --- /dev/null
>>>>>>> +++ b/drivers/clk/clk-k210.c
>>>>
>>>>>>> + in0_clk = of_clk_get(np, 0);
>>>>>>> + if (IS_ERR(in0_clk)) {
>>>>>>> + pr_warn("%pOFP: in0 oscillator not found\n", np);
>>>>>>> + hws[K210_CLK_IN0] =
>>>>>>> + clk_hw_register_fixed_rate(NULL, "in0", NULL,
>>>>>>> + 0, K210_IN0_RATE);
>>>>>>> + } else {
>>>>>>> + hws[K210_CLK_IN0] = __clk_get_hw(in0_clk);
>>>>>>> + }
>>>>>>> + if (IS_ERR(hws[K210_CLK_IN0])) {
>>>>>>> + pr_err("%pOFP: failed to get base oscillator\n", np);
>>>>>>> + goto err;
>>>>>>> + }
>>>>>>> +
>>>>>>> + in0 = clk_hw_get_name(hws[K210_CLK_IN0]);
>>>>>>> + aclk_parents[0] = in0;
>>>>>>> + pll_parents[0] = in0;
>>>>>>> + mux_parents[0] = in0;
>>>>>>
>>>>>> Can we use the new way of specifying clk parents so that we don't have
>>>>>> to use __clk_get_hw(), of_clk_get(), and clk_hw_get_name()? Hopefully
>>>>>> the core can handl that all instead of this driver.
>>>>>
>>>>> I removed all this by adding:
>>>>>
>>>>> clock-output-names = "in0";
>>>>>
>>>>> to the DT fixed-rate oscillator clock node (and documented that too). Doing so,
>>>>> clk_hw_get_name(), __clk_get_hw() and of_clk_get() are not needed anymore and
>>>>> the parents clock names arrays do not need run-time update.
>>>>
>>>> "clock-output-names" is deprecated for clocks with a single output:
>>>> the clock name will be taken from the node name.
>>>
>>> Arg. I missed that.
>>>
>>>> However, relying on a clock name like this is fragile.
>>>> Instead, your driver should use the phandle from the clocks property,
>>>> using of_clk_get_by_name() or of_clk_get().
>>>
>>> That is what all versions before V5 used. But Stephen mentioned that the driver
>>> should not, if possible, use of_clk_get()/__clk_get_name(). Hence the change.
>>> Easy to revert back.
>>>
>>>> Stephen: I'm a bit puzzled, as you suggest _not_ using of_clk_get()?
>>>
>>> Another solution to this would be to simply remove the fixed-rate clock node
>>> from the DT and have the k210 clock driver unconditionally create that clock
>>> (that is one line !). That actually may be even more simple than the previous
>>> version, albeit at the cost of having the DT not being a perfect description of
>>> the hardware. I am fine with that though.
>>>
>>> Thoughts ?
>>
>> If there's an external crystal, DT should describe it.
>> Does the K210 support different crystal frequencies?
>
> I am not 100% sure if this oscillator is part of the SoC or if it is an external
> input to it. Probably not. Hard to tell by just looking at the boards.
It's an external crystal. For example, it is U6 on the maix bit. This is
why I put it as a separate clock instead of including it with the rest.
--Sean
> I have
> the boards drawings though, so I will check. The frequency seems to be fixed by
> hardware: frequencies of the PLLs can be changed to change the CPU frequency,
> but the Kendryte SDK does not point to any way allowing changing the base
> frequency of the oscillator>
>> Anyway, I'm very interested in what the (new) proper way of handling this
>> is...
>>
>> Gr{oetje,eeting}s,
>>
>> Geert
>>
>> --
>> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>>
>> In personal conversations with technical people, I call myself a hacker. But
>> when I'm talking to journalists I just say "programmer" or something like that.
>> -- Linus Torvalds
>>
>
>
next prev parent reply other threads:[~2020-12-07 22:59 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 3:24 [PATCH v4 00/21] RISC-V Kendryte K210 support improvements Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 01/21] riscv: Fix kernel time_init() Damien Le Moal
2020-12-05 5:41 ` Stephen Boyd
2020-12-02 3:24 ` [PATCH v4 02/21] riscv: Fix sifive serial driver Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 03/21] riscv: Enable interrupts during syscalls with M-Mode Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 04/21] riscv: Fix builtin DTB handling Damien Le Moal
2020-12-04 15:11 ` Geert Uytterhoeven
2020-12-02 3:24 ` [PATCH v4 05/21] riscv: Use vendor name for K210 SoC support Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 06/21] dt-bindings: Add Canaan vendor prefix Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 07/21] dt-binding: clock: Document canaan,k210-clk bindings Damien Le Moal
2020-12-05 5:46 ` Stephen Boyd
2020-12-02 3:24 ` [PATCH v4 08/21] dt-bindings: reset: Document canaan,k210-rst bindings Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 09/21] dt-bindings: pinctrl: Document canaan,k210-fpioa bindings Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 10/21] dt-binding: mfd: Document canaan,k210-sysctl bindings Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 11/21] riscv: Add Canaan Kendryte K210 clock driver Damien Le Moal
2020-12-05 6:19 ` Stephen Boyd
2020-12-05 7:43 ` Damien Le Moal
2020-12-05 13:43 ` Sean Anderson
2020-12-05 14:13 ` Damien Le Moal
[not found] ` <160736612827.1580929.7802371235304556600@swboyd.mtv.corp.google.com>
2020-12-08 7:48 ` Damien Le Moal
2020-12-07 3:50 ` Damien Le Moal
2020-12-07 8:43 ` Geert Uytterhoeven
2020-12-07 9:55 ` Damien Le Moal
2020-12-07 10:06 ` Geert Uytterhoeven
2020-12-07 10:14 ` Damien Le Moal
2020-12-07 22:58 ` Sean Anderson [this message]
2020-12-07 11:34 ` Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 12/21] riscv: Add Canaan Kendryte K210 FPIOA driver Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 13/21] riscv: Add Canaan Kendryte K210 reset controller Damien Le Moal
2020-12-04 10:49 ` Philipp Zabel
2020-12-04 11:16 ` Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 14/21] riscv: Update Canaan Kendryte K210 device tree Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 15/21] riscv: Add SiPeed MAIX BiT board " Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 16/21] riscv: Add SiPeed MAIX DOCK " Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 17/21] riscv: Add SiPeed MAIX GO " Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 18/21] riscv: Add SiPeed MAIXDUINO " Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 19/21] riscv: Add Kendryte KD233 " Damien Le Moal
2020-12-02 3:24 ` [PATCH v4 20/21] riscv: Update Canaan Kendryte K210 defconfig Damien Le Moal
2020-12-02 3:25 ` [PATCH v4 21/21] riscv: Add Canaan Kendryte K210 SD card defconfig Damien Le Moal
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