From: Joel Fernandes <joelagn...@nvidia.com>
devinit is mentioned in the code. This patch explains it so it is clear
what it does. devinit is not only essential at boot-time, but also at
runtime due to suspend-resume and things like re-clocking.
Signed-off-by: Joel Fernandes <joelagn...@nvidia.com>
Reviewed-by: Bagas Sanjaya <bagasdo...@gmail.com>
Signed-off-by: Alexandre Courbot <acour...@nvidia.com>
---
Documentation/gpu/nova/core/devinit.rst | 61 +++++++++++++++++++++++++++++++++
Documentation/gpu/nova/index.rst | 1 +
2 files changed, 62 insertions(+)
diff --git a/Documentation/gpu/nova/core/devinit.rst
b/Documentation/gpu/nova/core/devinit.rst
new file mode 100644
index
0000000000000000000000000000000000000000..70c819a96a00a0a27846e7e96525470d07721a10
--- /dev/null
+++ b/Documentation/gpu/nova/core/devinit.rst
@@ -0,0 +1,61 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
+Device Initialization (devinit)
+==================================
+The devinit process is complex and subject to change. This document provides a
high-level
+overview using the Ampere GPU family as an example. The goal is to provide a
conceptual
+overview of the process to aid in understanding the corresponding kernel code.
+
+Device initialization (devinit) is a crucial sequence of register read/write
operations
+that occur after a GPU reset. The devinit sequence is essential for properly
configuring
+the GPU hardware before it can be used.
+
+The devinit engine is an interpreter program that typically runs on the PMU
(Power Management
+Unit) microcontroller of the GPU. This interpreter executes a "script" of
initialization
+commands. The devinit engine itself is part of the VBIOS ROM in the same ROM
image as the
+FWSEC (Firmware Security) image (see fwsec.rst and vbios.rst) and it runs
before the
+nova-core driver is even loaded. On an Ampere GPU, the devinit ucode is
separate from the
+FWSEC ucode. It is launched by FWSEC, which runs on the GSP in 'heavy-secure'
mode, while
+devinit runs on the PMU in 'light-secure' mode.
+
+Key Functions of devinit
+------------------------
+devinit performs several critical tasks:
+
+1. Programming VRAM memory controller timings
+2. Power sequencing
+3. Clock and PLL (Phase-Locked Loop) configuration
+4. Thermal management
+
+Low-level Firmware Initialization Flow
+--------------------------------------
+Upon reset, several microcontrollers on the GPU (such as PMU, SEC2, GSP, etc.)
run GPU
+firmware (gfw) code to set up the GPU and its core parameters. Most of the GPU
is
+considered unusable until this initialization process completes.
+
+These low-level GPU firmware components are typically:
+
+1. Located in the VBIOS ROM in the same ROM partition (see vbios.rst and
fwsec.rst).
+2. Executed in sequence on different microcontrollers:
+
+ - The devinit engine typically but not necessarily runs on the PMU.
+ - On an Ampere GPU, the FWSEC typically runs on the GSP (GPU System
Processor) in
+ heavy-secure mode.
+
+Before the driver can proceed with further initialization, it must wait for a
signal
+indicating that core initialization is complete (known as GFW_BOOT). This
signal is
+asserted by the FWSEC running on the GSP in heavy-secure mode.
+
+Runtime Considerations
+----------------------
+It's important to note that the devinit sequence also needs to run during
suspend/resume
+operations at runtime, not just during initial boot, as it is critical to
power management.
+
+Security and Access Control
+---------------------------
+The initialization process involves careful privilege management. For example,
before
+accessing certain completion status registers, the driver must check privilege
level
+masks. Some registers are only accessible after secure firmware (FWSEC) lowers
the
+privilege level to allow CPU (LS/low-secure) access. This is the case, for
example,
+when receiving the GFW_BOOT signal.
\ No newline at end of file
diff --git a/Documentation/gpu/nova/index.rst b/Documentation/gpu/nova/index.rst
index
f38041fcd595524b204eabf6ca3aad51038682cf..e4e017d926767284b5cee844d8dba32be6bc064c
100644
--- a/Documentation/gpu/nova/index.rst
+++ b/Documentation/gpu/nova/index.rst
@@ -29,3 +29,4 @@ vGPU manager VFIO driver and the nova-drm driver.
core/guidelines
core/todo
core/vbios
+ core/devinit
--
2.50.0
