linux-kernel - Re: [PATCH 4/7] docs: gpu: nova-core: Document the PRAMIN aperture mechanism

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Message-ID: <aPg8wuF5ZodLxOH0@archie.me>
Date: Wed, 22 Oct 2025 09:09:06 +0700
From: Bagas Sanjaya <bagasdotme@...il.com>
To: Joel Fernandes <joelagnelf@...dia.com>, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	dakr@...nel.org, acourbot@...dia.com
Cc: Alistair Popple <apopple@...dia.com>, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	bjorn3_gh@...tonmail.com, Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	John Hubbard <jhubbard@...dia.com>, Timur Tabi <ttabi@...dia.com>,
	joel@...lfernandes.org, Elle Rhumsaa <elle@...thered-steel.dev>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	nouveau@...ts.freedesktop.org
Subject: Re: [PATCH 4/7] docs: gpu: nova-core: Document the PRAMIN aperture
 mechanism

On Mon, Oct 20, 2025 at 02:55:36PM -0400, Joel Fernandes wrote:
> +The window position is controlled via the PBUS BAR0_WINDOW register::
> +
> +    NV_PBUS_BAR0_WINDOW Register
> +    +-----+-----+--------------------------------------+
> +    |31-26|25-24|           23-0                       |
> +    |     |TARG |         BASE_ADDR                    |
> +    |     | ET  |        (bits 39:16 of VRAM address)  |
> +    +-----+-----+--------------------------------------+

Shouldn't the TARGET field cell above be fitted (extended)?

> +
> +    TARGET field values:
> +    - 0x0: VID_MEM (Video Memory / VRAM)
> +    - 0x1: SYS_MEM_COHERENT (Coherent system memory)
> +    - 0x2: SYS_MEM_NONCOHERENT (Non-coherent system memory)
> +
> +64KB Alignment Requirement
> +---------------------------
> +
> +The PRAMIN window must be aligned to 64KB boundaries in VRAM. This is enforced
> +by the BASE_ADDR field representing bits [39:16] of the target address::
> +
> +    VRAM Address Calculation:
> +    actual_vram_addr = (BASE_ADDR << 16) + pramin_offset
> +    Where:
> +    - BASE_ADDR: 24-bit value from NV_PBUS_BAR0_WINDOW[23:0]
> +    - pramin_offset: 20-bit offset within PRAMIN window [0x00000-0xFFFFF]
> +    Example Window Positioning:

Move the supplementary explanation out of respective literal code blocks,
like::

---- >8 ----
diff --git a/Documentation/gpu/nova/core/pramin.rst b/Documentation/gpu/nova/core/pramin.rst
index 19615e504db9d5..47abe539e32a81 100644
--- a/Documentation/gpu/nova/core/pramin.rst
+++ b/Documentation/gpu/nova/core/pramin.rst
@@ -70,23 +70,28 @@ The window position is controlled via the PBUS BAR0_WINDOW register::
     |     | ET  |        (bits 39:16 of VRAM address)  |
     +-----+-----+--------------------------------------+
 
-    TARGET field values:
-    - 0x0: VID_MEM (Video Memory / VRAM)
-    - 0x1: SYS_MEM_COHERENT (Coherent system memory)
-    - 0x2: SYS_MEM_NONCOHERENT (Non-coherent system memory)
+where TARGET field values are:
+
+  - 0x0: VID_MEM (Video Memory / VRAM)
+  - 0x1: SYS_MEM_COHERENT (Coherent system memory)
+  - 0x2: SYS_MEM_NONCOHERENT (Non-coherent system memory)
 
 64KB Alignment Requirement
 ---------------------------
 
 The PRAMIN window must be aligned to 64KB boundaries in VRAM. This is enforced
-by the BASE_ADDR field representing bits [39:16] of the target address::
+by the BASE_ADDR field representing bits [39:16] of the target address. The
+VRAM address calculation is determined by::
 
-    VRAM Address Calculation:
     actual_vram_addr = (BASE_ADDR << 16) + pramin_offset
-    Where:
-    - BASE_ADDR: 24-bit value from NV_PBUS_BAR0_WINDOW[23:0]
-    - pramin_offset: 20-bit offset within PRAMIN window [0x00000-0xFFFFF]
-    Example Window Positioning:
+
+where:
+
+  - BASE_ADDR: 24-bit value from NV_PBUS_BAR0_WINDOW[23:0]
+  - pramin_offset: 20-bit offset within PRAMIN window [0x00000-0xFFFFF]
+
+Example window positioning::
+
     +---------------------------------------------------------+
     |                    VRAM Space                           |
     |                                                         |

Thanks. 

-- 
An old man doll... just what I always wanted! - Clara

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