diff mbox series

[v3,22/24] dmaengine: dw-edma: Bypass dma-ranges mapping for the local setup

Message ID 20220610091459.17612-23-Sergey.Semin@baikalelectronics.ru (mailing list archive)
State Handled Elsewhere
Headers show
Series dmaengine: dw-edma: Add RP/EP local DMA controllers support | expand

Commit Message

Serge Semin June 10, 2022, 9:14 a.m. UTC
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>

---

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(+)

Comments

Manivannan Sadhasivam July 9, 2022, 8:31 a.m. UTC | #1
On Fri, Jun 10, 2022 at 12:14:57PM +0300, Serge Semin wrote:
> 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>

Thanks,
Mani

> 
> ---
> 
> 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
>
diff mbox series

Patch

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;