linux-kernel - Re: [PATCH v5 1/8] power: sequencing: Add T-HEAD TH1520 GPU power sequencer driver

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Message-ID: <aFNDwcK5+ZuHBdrw@x1>
Date: Wed, 18 Jun 2025 15:54:57 -0700
From: Drew Fustini <drew@...7.com>
To: Michal Wilczynski <m.wilczynski@...sung.com>
Cc: Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Frank Binns <frank.binns@...tec.com>,
	Matt Coster <matt.coster@...tec.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v5 1/8] power: sequencing: Add T-HEAD TH1520 GPU power
 sequencer driver

On Wed, Jun 18, 2025 at 12:22:07PM +0200, Michal Wilczynski wrote:
> Introduce the pwrseq-thead-gpu driver, a power sequencer provider for
> the Imagination BXM-4-64 GPU on the T-HEAD TH1520 SoC. This driver
> controls an auxiliary device instantiated by the AON power domain.
> 
> The TH1520 GPU requires a specific sequence to correctly initialize and
> power down its resources:
>  - Enable GPU clocks (core and sys).
>  - De-assert the GPU clock generator reset (clkgen_reset).
>  - Introduce a short hardware-required delay.
>  - De-assert the GPU core reset. The power-down sequence performs these
>    steps in reverse.
> 
> Implement this sequence via the pwrseq_power_on and pwrseq_power_off
> callbacks.
> 
> Crucially, the driver's match function is called when a consumer (the
> Imagination GPU driver) requests the "gpu-power" target. During this
> match, the sequencer uses clk_bulk_get() and
> reset_control_get_exclusive() on the consumer's device to obtain handles
> to the GPU's "core" and "sys" clocks, and the GPU core reset.  These,
> along with clkgen_reset obtained from parent aon node, allow it to
> perform the complete sequence.
> 
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>
> ---
>  MAINTAINERS                                 |   1 +
>  drivers/power/sequencing/Kconfig            |   8 +
>  drivers/power/sequencing/Makefile           |   1 +
>  drivers/power/sequencing/pwrseq-thead-gpu.c | 231 ++++++++++++++++++++++++++++
>  4 files changed, 241 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 0183c028fa18c397d30ec82fd419894f1f50a448..3283ff592215249bcf702dbb4ab710477243477e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -21395,6 +21395,7 @@ F:	drivers/mailbox/mailbox-th1520.c
>  F:	drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
>  F:	drivers/pinctrl/pinctrl-th1520.c
>  F:	drivers/pmdomain/thead/
> +F:	drivers/power/sequencing/pwrseq-thead-gpu.c
>  F:	drivers/reset/reset-th1520.c
>  F:	include/dt-bindings/clock/thead,th1520-clk-ap.h
>  F:	include/dt-bindings/power/thead,th1520-power.h
> diff --git a/drivers/power/sequencing/Kconfig b/drivers/power/sequencing/Kconfig
> index ddcc42a984921c55667c46ac586d259625e1f1a7..7fa912c9af2479cdce909467c29fe335788f0bd7 100644
> --- a/drivers/power/sequencing/Kconfig
> +++ b/drivers/power/sequencing/Kconfig
> @@ -27,4 +27,12 @@ config POWER_SEQUENCING_QCOM_WCN
>  	  this driver is needed for correct power control or else we'd risk not
>  	  respecting the required delays between enabling Bluetooth and WLAN.
>  
> +config POWER_SEQUENCING_THEAD_GPU
> +	tristate "T-HEAD TH1520 GPU power sequencing driver"
> +	depends on ARCH_THEAD && AUXILIARY_BUS
> +	help
> +	  Say Y here to enable the power sequencing driver for the TH1520 SoC
> +	  GPU. This driver handles the complex clock and reset sequence
> +	  required to power on the Imagination BXM GPU on this platform.

This is a minor nit but maybe this should be POWER_SEQUENCING_TH1520_GPU?

I often grep for TH1520 to make sure I have all the options enabled and
it took me a second to realize it was 'THEAD' instead of 'TH1520'.

In retrospect, I probably should have have used CONFIG_DWMAC_TH1520 for
the ethernet driver instead of CONFIG_DWMAC_THEAD.

Thanks,
Drew