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[ Upstream commit cec9771d2e954650095aa37a6a97722c8194e7d2 ] +----------+ +----------+ | | | | | |--- 3.0 G ---| |--- 6.0 G --- SAS disk | | | | | |--- 3.0 G ---| |--- 6.0 G --- SAS disk |initiator | | | | device |--- 3.0 G ---| Expander |--- 6.0 G --- SAS disk | | | | | |--- 3.0 G ---| |--- 6.0 G --- SATA disk -->failed to connect | | | | | | | |--- 6.0 G --- SATA disk -->failed to connect | | | | +----------+ +----------+ According to Serial Attached SCSI - 1.1 (SAS-1.1): If an expander PHY attached to a SATA PHY is using a physical link rate greater than the maximum connection rate supported by the pathway from an STP initiator port, a management application client should use the SMP PHY CONTROL function (see 10.4.3.10) to set the PROGRAMMED MAXIMUM PHYSICAL LINK RATE field of the expander PHY to the maximum connection rate supported by the pathway from that STP initiator port. Currently libsas does not support checking if this condition occurs, nor rectifying when it does. Such a condition is not at all common, however it has been seen on some pre-silicon environments where the initiator PHY only supports a 1.5 Gbit maximum linkrate, mated with 12G expander PHYs and 3/6G SATA phy. This patch adds support for checking and rectifying this condition during initial device discovery only. We do support checking min pathway connection rate during revalidation phase, when new devices can be detected in the topology. However we do not support in the case of the the user reprogramming PHY linkrates, such that min pathway condition is not met/maintained. A note on root port PHY rates: The libsas root port PHY rates calculation is broken. Libsas sets the rates (min, max, and current linkrate) of a root port to the same linkrate of the first PHY member of that same port. In doing so, it assumes that all other PHYs which subsequently join the port to have the same negotiated linkrate, when they could actually be different. In practice this doesn't happen, as initiator and expander PHYs are normally initialised with consistent min/max linkrates. This has not caused an issue so far, so leave alone for now. Tested-by: Jian Luo <luojian5@huawei.com> Signed-off-by: John Garry <john.garry@huawei.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.