mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-04-18 23:09:58 -04:00
7ad06f2184
The interleaved DMA transfer support added by85e7518f42("dmaengine: dw-edma: Add device_prep_interleave_dma() support") seems contradictory to what the DMA engine defines. The next conditional statements: if (!xfer->xfer.il->numf) return NULL; if (xfer->xfer.il->numf > 0 && xfer->xfer.il->frame_size > 0) return NULL; mean that numf can't be zero and frame_size must always be zero, otherwise the transfer won't be executed. Furthermore, the transfer execution method takes the frame size from the dma_interleaved_template.sgl[] array for each frame. That array in accordance with [1] is supposed to be of dma_interleaved_template.frame_size size, which as we discovered before the code expects to be zero. So judging by the dw_edma_device_transfer() implementation, the method implies the dma_interleaved_template.sgl[] array being of dma_interleaved_template.numf size, which is wrong. Since the dw_edma_device_transfer() method doesn't permit dma_interleaved_template.frame_size being non-zero, the multi-chunk interleaved transfer turns to be unsupported even though the code implies having it supported. Add fully functioning support of interleaved DMA transfers. First of all, dma_interleaved_template.frame_size is supposed to be greater or equal to one thus having at least simple linear chunked frames. Secondly, we can create a walk-through over all the chunks and frames by initializing the number of the eDMA burst transactions as a multiple of dma_interleaved_template.numf and dma_interleaved_template.frame_size and getting the frame_size-modulo of the iteration step as an index of the dma_interleaved_template.sgl[] array. [1] include/linux/dmaengine.h: doc struct dma_interleaved_template Link: https://lore.kernel.org/r/20230113171409.30470-7-Sergey.Semin@baikalelectronics.ru Fixes:85e7518f42("dmaengine: dw-edma: Add device_prep_interleave_dma() support") Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Acked-by: Vinod Koul <vkoul@kernel.org>
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.