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5e85bff62b
W35N{01,02,04}JW support being read continuously under certain
circumstances. A bit must be set in their configuration register, and
a specific read from cache operation, a bit shorter than usual because
it no longer requires the address cycles, must be used for the occasion.
Setting the "enable" bit is already supported by the core, aside from
the subtlety of making sure the HFREQ bit is also set in octal DTR mode
above 90MHz. However, handling two different read from cache templates
involves creating a list of read from cache variants adapted the
continuous reads, ie. without address cycles.
Unfortunately, these operations, despite being very close to their
original read from cache cousins, are often unsupported by smart SPI
controller drivers because reading from cache historically allowed
changing the offset at which the host would start by providing a 2-byte
column address. In order to prevent issues with this, it has been
decided to implement these variants with a single "ignored" address byte
(respectively two in the octal DTR case), further reducing the amount of
dummy cycles needed before the first bit of data.
Enabling continuous reads has a side effect: the ECC status register now
may also return the value b11, which means that more than 1
uncorrectable error happened during the read. This non standard
behaviour requires to re-implement, almost identically the "get ECC"
helper from the core, with just an extra case for this value (it is
prefixed "w25w35nxxjw" because all these chips have the same behaviour).
Speed gain is substantial, see below. The flash_speed -C benchmark has
been run on a TI AM62A7 LP SK with CPU power management disabled,
mounted with a W35N01JW chip.
1S-8S-8S:
1 page read speed is 15058 KiB/s
2 page read speed is 15058 KiB/s
3 page read speed is 16800 KiB/s
4 page read speed is 17066 KiB/s
5 page read speed is 18461 KiB/s
6 page read speed is 18461 KiB/s
7 page read speed is 19384 KiB/s
8 page read speed is 19692 KiB/s
9 page read speed is 19384 KiB/s
10 page read speed is 20000 KiB/s
11 page read speed is 20000 KiB/s
12 page read speed is 20000 KiB/s
13 page read speed is 20800 KiB/s
14 page read speed is 20363 KiB/s
15 page read speed is 20000 KiB/s
16 page read speed is 19692 KiB/s
32 page read speed is 19692 KiB/s
64 page read speed is 19692 KiB/s
8D-8D-8D:
1 page read speed is 23272 KiB/s
2 page read speed is 23272 KiB/s
3 page read speed is 28000 KiB/s
4 page read speed is 32000 KiB/s
5 page read speed is 34285 KiB/s
6 page read speed is 34285 KiB/s
7 page read speed is 36000 KiB/s
8 page read speed is 36571 KiB/s
9 page read speed is 36000 KiB/s
10 page read speed is 34285 KiB/s
11 page read speed is 36666 KiB/s
12 page read speed is 40000 KiB/s
13 page read speed is 41600 KiB/s
14 page read speed is 37333 KiB/s
15 page read speed is 40000 KiB/s
16 page read speed is 36571 KiB/s
32 page read speed is 42666 KiB/s
64 page read speed is 42666 KiB/s
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
Not all configurations have been tested/validated yet.
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| README | ||
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst