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[ Upstream commitaf424a4107] The commit3bc04e28a0("usb: dwc2: host: Get aligned DMA in a more supported way") rips out a lot of code to simply the allocation of aligned DMA. However, it also introduces a new issue when use isoc split in transfer. In my test case, I connect the dwc2 controller with an usb hs Hub (GL852G-12), and plug an usb fs audio device (Plantronics headset) into the downstream port of Hub. Then use the usb mic to record, we can find noise when playback. It's because that the usb Hub uses an MDATA for the first transaction and a DATA0 for the second transaction for the isoc split in transaction. An typical isoc split in transaction sequence like this: - SSPLIT IN transaction - CSPLIT IN transaction - MDATA packet - CSPLIT IN transaction - DATA0 packet The DMA address of MDATA (urb->dma) is always DWORD-aligned, but the DMA address of DATA0 (urb->dma + qtd->isoc_split_offset) may not be DWORD-aligned, it depends on the qtd->isoc_split_offset (the length of MDATA). In my test case, the length of MDATA is usually unaligned, this cause DATA0 packet transmission error. This patch use kmem_cache to allocate aligned DMA buf for isoc split in transaction. Note that according to usb 2.0 spec, the maximum data payload size is 1023 bytes for each fs isoc ep, and the maximum allowable interrupt data payload size is 64 bytes or less for fs interrupt ep. So we set the size of object to be 1024 bytes in the kmem cache. Tested-by: Gevorg Sahakyan <sahakyan@synopsys.com> Tested-by: Heiko Stuebner <heiko@sntech.de> Acked-by: Minas Harutyunyan hminas@synopsys.com> Signed-off-by: William Wu <william.wu@rock-chips.com> Reviewed-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.