linux-kernel - Re: [PATCH v5 13/21] drm/imagination: Add reset controller support for GPU initialization

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Message-ID: <60914de9-f507-4099-be53-ea1fc282c537@samsung.com>
Date: Wed, 16 Apr 2025 16:25:04 +0200
From: Michal Wilczynski <m.wilczynski@...sung.com>
To: frank.binns@...tec.com, matt.coster@...tec.com
Cc: p.zabel@...gutronix.de, m.szyprowski@...sung.com,
	linux-clk@...r.kernel.org, conor+dt@...nel.org, devicetree@...r.kernel.org,
	mripard@...nel.org, linux-kernel@...r.kernel.org, tzimmermann@...e.de,
	linux-riscv@...ts.infradead.org, airlied@...il.com, simona@...ll.ch,
	aou@...s.berkeley.edu, dri-devel@...ts.freedesktop.org,
	ulf.hansson@...aro.org, linux-pm@...r.kernel.org, jszhang@...nel.org,
	palmer@...belt.com, guoren@...nel.org, maarten.lankhorst@...ux.intel.com,
	wefu@...hat.com, paul.walmsley@...ive.com, jassisinghbrar@...il.com,
	drew@...7.com, robh@...nel.org, sboyd@...nel.org, mturquette@...libre.com,
	krzk+dt@...nel.org
Subject: Re: [PATCH v5 13/21] drm/imagination: Add reset controller support
 for GPU initialization



On 2/19/25 15:02, Michal Wilczynski wrote:
> All IMG Rogue GPUs include a reset line that participates in the
> power-up sequence. On some SoCs (e.g., T-Head TH1520 and Banana Pi
> BPI-F3), this reset line is exposed and must be driven explicitly to
> ensure proper initialization.  On others, such as the currently
> supported TI SoC, the reset logic is handled in hardware or firmware
> without exposing the line directly. In platforms where the reset line is
> externally accessible, if it is not driven correctly, the GPU may remain
> in an undefined state, leading to instability or performance issues.
> 
> This commit adds a dedicated reset controller to the drm/imagination
> driver.  By managing the reset line (where applicable) as part of normal
> GPU bring-up, the driver ensures reliable initialization across
> platforms regardless of whether the reset is controlled externally or
> handled internally.
> 
> Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>
> ---
>  drivers/gpu/drm/imagination/pvr_device.c | 21 +++++++++++++++++++++
>  drivers/gpu/drm/imagination/pvr_device.h |  9 +++++++++
>  drivers/gpu/drm/imagination/pvr_power.c  | 22 +++++++++++++++++++++-
>  3 files changed, 51 insertions(+), 1 deletion(-)
> 

Hi Matt,

This commit, along with the corresponding change in the DT bindings,
doesn’t appear to conflict with the work you're doing for Rogue series
enablement.

Would you prefer if I re-send them as a mini-series so you can consider
picking them up for the next kernel release?

Regards,
Michał