linux-kernel - Re: [PATCH v2 4/9] drm/panthor: Move GPU info initialization into panthor

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Message-ID: <20250321094351.537c768c@collabora.com>
Date: Fri, 21 Mar 2025 09:43:51 +0100
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Karunika Choo <karunika.choo@....com>
Cc: dri-devel@...ts.freedesktop.org, nd@....com, Steven Price
 <steven.price@....com>, Liviu Dudau <liviu.dudau@....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>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/9] drm/panthor: Move GPU info initialization into
 panthor_hw.c

On Fri, 21 Mar 2025 09:16:45 +0100
Boris Brezillon <boris.brezillon@...labora.com> wrote:

> On Thu, 20 Mar 2025 11:17:36 +0000
> Karunika Choo <karunika.choo@....com> wrote:
> 
> > This patch moves GPU info initialization into panthor_hw.c in
> > preparation of handling GPU register changes. The GPU register reading
> > operations to populate gpu_info are separated into an architecture
> > specific arch_*_gpu_info_init() function and is called via the new
> > function pointer abstraction under hw.ops.gpu_info_init().
> > 
> > Future GPU support will be performed by implementing a *_gpu_info_init()
> > function specific to that architecture version. It can call any existing
> > *_gpu_info_init() and extend it with additional register reads or
> > provide an entirely different implementation.  
> 
> Could you give us an insight into what the reg layout changes are? So
> far, they were mostly unchanged between GPU gens, and I'd really
> prefer we could keep the majority of them unchanged part of the commo 
> discovery, and only add the missing reads in the ->gpu_info_init()
> callback.
> 
> Note that I'm also working on abstracting mali device operations to add
> JM support to panthor, and the only things I had to specialize are:
> 
> - CSF ID for CSF
> - JS features/present masks for JM
> 
> The rest is just common. So what I have is a common gpu_init_info()
> helper that reads all the regs excepts those two, and after that, I
> have a device ops selection based on the arch major of the GPU ID [1].
> The device-specific GPU info are then read as part of the
> panthor_device_ops::init().

With the link this time :-).

[1]https://gitlab.freedesktop.org/bbrezillon/linux/-/blob/panthor-jm/drivers/gpu/drm/panthor/panthor_device.c?ref_type=heads#L359