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9c63b846e6Merge series from Cédric Le Goater <clg@kaod.org>: This series adds a new SPI driver using the spi-mem interface for the Aspeed static memory controllers of the AST2600, AST2500 and AST2400 SoCs. * AST2600 Firmware SPI Memory Controller (FMC) * AST2600 SPI Flash Controller (SPI1 and SPI2) * AST2500 Firmware SPI Memory Controller (FMC) * AST2500 SPI Flash Controller (SPI1 and SPI2) * AST2400 New Static Memory Controller (also referred as FMC) * AST2400 SPI Flash Controller (SPI) It is based on the current OpenBMC kernel driver [1], using directly the MTD SPI-NOR interface and on a patchset [2] previously proposed adding support for the AST2600 only. This driver takes a slightly different approach to cover all 6 controllers. It does not make use of the controller register disabling Address and Data byte lanes because is not available on the AST2400 SoC. We could introduce a specific handler for new features available on recent SoCs if needed. As there is not much difference on performance, the driver chooses the common denominator: "User mode" which has been heavily tested in [1]. "User mode" is also used as a fall back method when flash device mapping window is too small. Problems to address with spi-mem were the configuration of the mapping windows and the calibration of the read timings. The driver handles them in the direct mapping handler when some knowledge on the size of the flash device is know. It is not perfect but not incorrect either. The algorithm is one from [1] because it doesn't require the DMA registers which are not available on all controllers. Direct mapping for writes is not supported (yet). I have seen some corruption with writes and I preferred to use the safer and proven method of the initial driver [1]. We can improve that later. The driver supports Quad SPI RX transfers on the AST2600 SoC but it didn't have the expected results. Therefore it is not activated yet. There are some issues on the pinctrl to investigate first. Tested on: * OpenPOWER Palmetto (AST2400) * Facebook Wedge 100 BMC (AST2400) by Tao Ren <rentao.bupt@gmail.com> * Evaluation board (AST2500) * Inspur FP5280G2 BMC (AST2500) by John Wang <wangzq.jn@gmail.com> * Facebook Backpack CMM BMC (AST2500) by Tao Ren <rentao.bupt@gmail.com> * OpenPOWER Witherspoon (AST2500) * Evaluation board (AST2600 A0 and A3) * Rainier board (AST2600) [1] https://github.com/openbmc/linux/blob/dev-5.15/drivers/mtd/spi-nor/controllers/aspeed-smc.c [2] https://patchwork.ozlabs.org/project/linux-aspeed/list/?series=212394 |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.