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[v2,23/26] dmaengine: dw-edma: Bypass dma-ranges mapping for the local setup

Message ID 20220503225104.12108-24-Sergey.Semin@baikalelectronics.ru (mailing list archive)
State Superseded
Delegated to: Lorenzo Pieralisi
Headers show
Series dmaengine: dw-edma: Add RP/EP local DMA controllers support | expand

Commit Message

Serge Semin May 3, 2022, 10:51 p.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>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

---

Changelog v2:
- Fix the comment a bit to being clearer. (@Manivannan)
---
 drivers/dma/dw-edma/dw-edma-core.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

Comments

Manivannan Sadhasivam May 24, 2022, 1:19 p.m. UTC | #1 
On Wed, May 04, 2022 at 01:51:01AM +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>
> 
> ---
> 
> Changelog v2:
> - Fix the comment a bit to being clearer. (@Manivannan)
> ---
>  drivers/dma/dw-edma/dw-edma-core.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index 6a8282eaebaf..908607785401 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -716,6 +716,21 @@ 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;
> +
> +		dchan->dev->device.dma_coherent = chan->dw->chip->dev->dma_coherent;

I happen to test this series on Qcom ARM32 machine and it errors out during the
compilation due to "dma_coherent" not available on !SWIOTLB ARM32 configs.

Thanks,
Mani

> +		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
>
Serge Semin May 25, 2022, 8:56 a.m. UTC | #2 
On Tue, May 24, 2022 at 06:49:59PM +0530, Manivannan Sadhasivam wrote:
> On Wed, May 04, 2022 at 01:51:01AM +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>
> > 
> > ---
> > 
> > Changelog v2:
> > - Fix the comment a bit to being clearer. (@Manivannan)
> > ---
> >  drivers/dma/dw-edma/dw-edma-core.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> > 
> > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > index 6a8282eaebaf..908607785401 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > @@ -716,6 +716,21 @@ 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;
> > +
> > +		dchan->dev->device.dma_coherent = chan->dw->chip->dev->dma_coherent;
> 

> I happen to test this series on Qcom ARM32 machine and it errors out during the
> compilation due to "dma_coherent" not available on !SWIOTLB ARM32 configs.

Nice catch! Thanks. I'll fix it in the next patchset version.

-Sergey

> 
> Thanks,
> Mani
> 
> > +		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
> > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்
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..908607785401 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -716,6 +716,21 @@  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;
+
+		dchan->dev->device.dma_coherent = chan->dw->chip->dev->dma_coherent;
+		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;