On Wed, Jul 02, 2025 at 08:00:42PM +0900, Alexandre Courbot wrote: > 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. The wording LGTM, thanks! Reviewed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> -- An old man doll... just what I always wanted! - Clara
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