linux-kernel - Re: [RFC v3 05/18] pmdomain: thead: Add power-domain driver for TH1520

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Message-ID: <9039d98b-ea3b-401a-804c-8c60ec714b99@samsung.com>
Date: Wed, 22 Jan 2025 12:26:35 +0100
From: Michal Wilczynski <m.wilczynski@...sung.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, drew@...7.com, guoren@...nel.org,
	wefu@...hat.com, jassisinghbrar@...il.com, paul.walmsley@...ive.com,
	palmer@...belt.com, aou@...s.berkeley.edu, frank.binns@...tec.com,
	matt.coster@...tec.com, maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
	ulf.hansson@...aro.org, jszhang@...nel.org, p.zabel@...gutronix.de,
	m.szyprowski@...sung.com, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
	linux-pm@...r.kernel.org
Subject: Re: [RFC v3 05/18] pmdomain: thead: Add power-domain driver for
 TH1520



On 1/22/25 08:46, Krzysztof Kozlowski wrote:
> On 21/01/2025 22:42, Michal Wilczynski wrote:
>>
>>
>> On 1/21/25 11:02, Krzysztof Kozlowski wrote:
>>> On Mon, Jan 20, 2025 at 06:20:58PM +0100, Michal Wilczynski wrote:
>>>> The T-Head TH1520 SoC contains multiple power islands that can be
>>>> programmatically turned on and off using the AON (Always-On) protocol
>>>> and a hardware mailbox [1]. The relevant mailbox driver has already been
>>>> merged into the mainline kernel in commit 5d4d263e1c6b ("mailbox:
>>>> Introduce support for T-head TH1520 Mailbox driver");
>>>>
>>>> This commit introduces a power-domain driver for the TH1520 SoC, which
>>>
>>> Please do not use "This commit/patch/change", but imperative mood. See
>>> longer explanation here:
>>> https://protect2.fireeye.com/v1/url?k=2123f702-40a8e22d-21227c4d-74fe485cbfe7-afb876722bdc8fc5&q=1&e=e5dabc89-5f0c-4819-9008-76faafc3c1bc&u=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv5.17.1%2Fsource%2FDocumentation%2Fprocess%2Fsubmitting-patches.rst%23L95
>>>
>>>> is using AON firmware protocol to communicate with E902 core through the
>>>> hardware mailbox. This way it can send power on/off commands to the E902
>>>> core.
>>>
>>> ...
>>>
>>>> diff --git a/drivers/pmdomain/thead/Makefile b/drivers/pmdomain/thead/Makefile
>>>> new file mode 100644
>>>> index 000000000000..adfdf5479c68
>>>> --- /dev/null
>>>> +++ b/drivers/pmdomain/thead/Makefile
>>>> @@ -0,0 +1,2 @@
>>>> +# SPDX-License-Identifier: GPL-2.0-only
>>>> +obj-$(CONFIG_TH1520_PM_DOMAINS)		+= th1520-pm-domains.o
>>>> diff --git a/drivers/pmdomain/thead/th1520-pm-domains.c b/drivers/pmdomain/thead/th1520-pm-domains.c
>>>> new file mode 100644
>>>> index 000000000000..d913ad40fb76
>>>> --- /dev/null
>>>> +++ b/drivers/pmdomain/thead/th1520-pm-domains.c
>>>> @@ -0,0 +1,174 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * Copyright (C) 2021 Alibaba Group Holding Limited.
>>>> + * Copyright (c) 2024 Samsung Electronics Co., Ltd.
>>>> + * Author: Michal Wilczynski <m.wilczynski@...sung.com>
>>>> + */
>>>> +
>>>> +#include <linux/firmware/thead/thead,th1520-aon.h>
>>>> +#include <linux/slab.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/pm_domain.h>
>>>> +
>>>> +#include <dt-bindings/firmware/thead,th1520-aon.h>
>>>
>>> So here it is used... I don't understand why power domain is under
>>> firmware. Please move it to proper directory and name the file exactly
>>> the same as bindings doc which this belongs to.
>>
>> The power-domain driver has no bindings doc. It's a child driver of the AON
>> node.
> 
> OK, not changing my comment, though.
> 
>>
>>>
>>>
>>>> +
>>>> +struct th1520_power_domain {
>>>> +	struct th1520_aon_chan *aon_chan;
>>>> +	struct generic_pm_domain genpd;
>>>> +	u32 rsrc;
>>>> +};
>>>> +
>>>> +struct th1520_power_info {
>>>> +	const char *name;
>>>> +	u32 rsrc;
>>>> +};
>>>> +
>>>> +static const struct th1520_power_info th1520_pd_ranges[] = {
>>>> +	{ "vdec", TH1520_AON_VDEC_PD },
>>>
>>> Why TH1520_AON_XXX aren't the indices?
>>
>> These power-domain constants are defined by the AON firmware protocol,
>> which dictates the exact IDs (e.g., 1 for NPU). They are not just array
>> indices; we must use these specific values to communicate with the
>> firmware correctly. Using array indices starting with 1 would be
>> unusual.
> 
> Then that's a no. Binding constants do not represent values used by your
> hardware. The binding constant should start from 0.

Would it be a problem if those overlapped ? There is one more value that
I skipped for now TH_1520_AON_AUDIO, that is indeed a 0. I skipped it
cause trying to turn it on/off, caused a crash in the firmware, which
stopped responding for a while. With this extra constant I would be able
to use those values as an indices, but would need to add extra code in
the driver to work around the issue.

> 
> Best regards,
> Krzysztof
>