[PATCH 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI

[PATCH 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI

[Bharat Kumar Gogada]

Add support for routing PCIe DMA traffic coherently when
Cache Coherent Interconnect (CCI) is enabled in the system.
The "dma-coherent" property is used to determine if CCI is enabled
or not.
Refer https://developer.arm.com/documentation/ddi0470/k/preface
for CCI specification.

Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>
---
 drivers/pci/controller/pcie-xilinx-nwl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c b/drivers/pci/controller/pcie-xilinx-nwl.c
index 07e36661bbc2..08e060574cb7 100644
--- a/drivers/pci/controller/pcie-xilinx-nwl.c
+++ b/drivers/pci/controller/pcie-xilinx-nwl.c
@@ -26,6 +26,7 @@
 
 /* Bridge core config registers */
 #define BRCFG_PCIE_RX0			0x00000000
+#define BRCFG_PCIE_RX1			0x00000004
 #define BRCFG_INTERRUPT			0x00000010
 #define BRCFG_PCIE_RX_MSG_FILTER	0x00000020
 
@@ -128,6 +129,7 @@
 #define NWL_ECAM_VALUE_DEFAULT		12
 
 #define CFG_DMA_REG_BAR			GENMASK(2, 0)
+#define CFG_PCIE_CACHE			GENMASK(7, 0)
 
 #define INT_PCI_MSI_NR			(2 * 32)
 
@@ -675,6 +677,12 @@ static int nwl_pcie_bridge_init(struct nwl_pcie *pcie)
 	nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
 			  BRCFG_PCIE_RX_MSG_FILTER);
 
+	/* This routes the PCIe DMA traffic to go through CCI path */
+	if (of_dma_is_coherent(dev->of_node)) {
+		nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, BRCFG_PCIE_RX1) |
+				  CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
+	}
+
 	err = nwl_wait_for_link(pcie);
 	if (err)
 		return err;
-- 
2.17.1

[PATCH 2/2] PCI: xilinx-nwl: Add optional "dma-coherent" property

[Bharat Kumar Gogada]

Add optional dma-coherent property to support coherent PCIe DMA traffic.

Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>
---
 Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt b/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
index 01bf7fdf4c19..2d677e90a7e2 100644
--- a/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
+++ b/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
@@ -33,6 +33,8 @@ Required properties:
 	- #address-cells: specifies the number of cells needed to encode an
 		address. The value must be 0.
 
+Optional properties:
+- dma-coherent: present if DMA operations are coherent
 
 Example:
 ++++++++
-- 
2.17.1

Re: [PATCH 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI

[Krzysztof Wilczyński]

Hi Bharat,

Thank you for sending the patches over!

> Add support for routing PCIe DMA traffic coherently when
> Cache Coherent Interconnect (CCI) is enabled in the system.
> The "dma-coherent" property is used to determine if CCI is enabled
> or not.
> Refer https://developer.arm.com/documentation/ddi0470/k/preface
> for CCI specification.
[...]

A small nitpick, so feel free to ignore, of course.

Perhaps "Refer to" and "for the CCI", etc.

[...]
> +	/* This routes the PCIe DMA traffic to go through CCI path */
> +	if (of_dma_is_coherent(dev->of_node)) {
> +		nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, BRCFG_PCIE_RX1) |
> +				  CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> +	}
[...]

A suggestion.

You can drop the curly brackets here if you want to keep the style used
in the kernel, especially for when there is a single statement inside
the code block.

Krzysztof

RE: [PATCH 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI

[Bharat Kumar Gogada]

> Hi Bharat,
> 
> Thank you for sending the patches over!
> 
> > Add support for routing PCIe DMA traffic coherently when Cache
> > Coherent Interconnect (CCI) is enabled in the system.
> > The "dma-coherent" property is used to determine if CCI is enabled or
> > not.
> > Refer https://developer.arm.com/documentation/ddi0470/k/preface
> > for CCI specification.
> [...]
> 
> A small nitpick, so feel free to ignore, of course.
> 
> Perhaps "Refer to" and "for the CCI", etc.
> 
> [...]
> > +	/* This routes the PCIe DMA traffic to go through CCI path */
> > +	if (of_dma_is_coherent(dev->of_node)) {
> > +		nwl_bridge_writel(pcie, nwl_bridge_readl(pcie,
> BRCFG_PCIE_RX1) |
> > +				  CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> > +	}
> [...]
> 
> A suggestion.
> 
> You can drop the curly brackets here if you want to keep the style used in
> the kernel, especially for when there is a single statement inside the code
> block.
> 
Thanks Krzysztof. Will remove it.