RE: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI

[Bharat Kumar Gogada <bharatku@xilinx.com>]

Ping.

> -----Original Message-----
> From: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>
> Sent: Monday, February 22, 2021 2:18 PM
> To: linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: bhelgaas@google.com; Bharat Kumar Gogada <bharatku@xilinx.com>
> Subject: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic
> using CCI
> 
> 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 to https://developer.arm.com/documentation/ddi0470/k/preface
> for the CCI specification.
> 
> Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>
> ---
>  drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c
> b/drivers/pci/controller/pcie-xilinx-nwl.c
> index 07e36661bbc2..8689311c5ef6 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 +677,11 @@ 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