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[ Upstream commit 181fa434d0514e40ebf6e9721f2b72700287b6e2 ] According to the PCI Local Bus specification Revision 3.0, section 6.8.1.3 (Message Control for MSI), endpoints that are Multiple Message Capable as defined by bits [3:1] in the Message Control for MSI can request a number of vectors that is power of two aligned. As specified in section 6.8.1.6 "Message data for MSI", the Multiple Message Enable field (bits [6:4] of the Message Control register) defines the number of low order message data bits the function is permitted to modify to generate its system software allocated vectors. The MSI controller in the Xilinx NWL PCIe controller supports a number of MSI vectors specified through a bitmap and the hwirq number for an MSI, that is the value written in the MSI data TLP is determined by the bitmap allocation. For instance, in a situation where two endpoints sitting on the PCI bus request the following MSI configuration, with the current PCI Xilinx bitmap allocation code (that does not align MSI vector allocation on a power of two boundary): Endpoint #1: Requesting 1 MSI vector - allocated bitmap bits 0 Endpoint #2: Requesting 2 MSI vectors - allocated bitmap bits [1,2] The bitmap value(s) corresponds to the hwirq number that is programmed into the Message Data for MSI field in the endpoint MSI capability and is detected by the root complex to fire the corresponding MSI irqs. The value written in Message Data for MSI field corresponds to the first bit allocated in the bitmap for Multi MSI vectors. The current Xilinx NWL MSI allocation code allows a bitmap allocation that is not a power of two boundaries, so endpoint #2, is allowed to toggle Message Data bit[0] to differentiate between its two vectors (meaning that the MSI data will be respectively 0x0 and 0x1 for the two vectors allocated to endpoint #2). This clearly aliases with the Endpoint #1 vector allocation, resulting in a broken Multi MSI implementation. Update the code to allocate MSI bitmap ranges with a power of two alignment, fixing the bug. Fixes: ab597d35ef11 ("PCI: xilinx-nwl: Add support for Xilinx NWL PCIe Host Controller") Suggested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com> [lorenzo.pieralisi@arm.com: updated commit log] Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Acked-by: Marc Zyngier <marc.zyngier@arm.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.