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AHCI provides the register PORTS_IMPL to let the software know which port is supported. The register must be initialized by the bootloader. However in some cases u-boot doesn't properly initialize this value (if it is not compiled with SATA support for example or if the SATA initialization fails). The DTS entry "ports-implemented" can be used to override the value in PORTS_IMPL. Without this patch the SATA will not work in the following two cases: * if there has been a failure to initialize SATA in u-boot. * if ahci_platform module has been removed and re-inserted. The reason is that the content of PORTS_IMPL is lost after the module is removed. I suspect that it's because the controller is reset by the hwmod. Cc: <stable@vger.kernel.org> # v4.6+ Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com> Acked-by: Roger Quadros <rogerq@ti.com> [tony@atomide.com: updated comments with what goes wrong] Signed-off-by: Tony Lindgren <tony@atomide.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.