[PATCH RESEND v5 22/24] dmaengine: dw-edma: Bypass dma-ranges mapping for the local setup

Serge Semin
2022-08-22T18:55:17Z

DW eDMA doesn't perform any translation of the traffic generated on the
CPU/Application side. It just generates read/write AXI-bus requests with
the specified addresses. But in case if the dma-ranges DT-property is
specified for a platform device node, Linux will use it to map the CPU
memory regions into the DMAable bus ranges. This isn't what we want for
the eDMA embedded into the locally accessed DW PCIe Root Port and
End-point. In order to work that around let's set the chan_dma_dev flag
for each DW eDMA channel thus forcing the client drivers to getting a
custom dma-ranges-less parental device for the mappings.

Note it will only work for the client drivers using the
dmaengine_get_dma_device() method to get the parental DMA device.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-By: Vinod Koul <vkoul@kernel.org>

---

Changelog v2:
- Fix the comment a bit to being clearer. (@Manivannan)

Changelog v3:
- Conditionally set dchan->dev->device.dma_coherent field since it can
be missing on some platforms. (@Manivannan)
- Remove Manivannan' rb and tb tags since the patch content has been
changed.
---
drivers/dma/dw-edma/dw-edma-core.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 6a8282eaebaf..4f56149dc8d8 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -716,6 +716,26 @@ static int dw_edma_alloc_chan_resources(struct dma_chan *dchan)
if (chan->status != EDMA_ST_IDLE)
return -EBUSY;

+ /* Bypass the dma-ranges based memory regions mapping for the eDMA
+ * controlled from the CPU/Application side since in that case
+ * the local memory address is left untranslated.
+ */
+ if (chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) {
+ dchan->dev->chan_dma_dev = true;
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
+ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
+ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
+ dchan->dev->device.dma_coherent = chan->dw->chip->dev->dma_coherent;
+#endif
+
+ dma_coerce_mask_and_coherent(&dchan->dev->device,
+ dma_get_mask(chan->dw->chip->dev));
+ dchan->dev->device.dma_parms = chan->dw->chip->dev->dma_parms;
+ } else {
+ dchan->dev->chan_dma_dev = false;
+ }
+
pm_runtime_get(chan->dw->chip->dev);

return 0;
--
2.35.1