linux-kernel - Re: [PATCH v9 08/27] dmaengine: dw-edma: Add PCIe bus address getter to the remote EP glue-driver

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Date:   Fri, 20 Jan 2023 17:29:20 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Cai Huoqing <cai.huoqing@...ux.dev>,
        Robin Murphy <robin.murphy@....com>,
        Jingoo Han <jingoohan1@...il.com>, Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Krzysztof Wilczyński <kw@...ux.com>,
        caihuoqing <caihuoqing@...du.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 08/27] dmaengine: dw-edma: Add PCIe bus address getter
 to the remote EP glue-driver

On Fri, Jan 13, 2023 at 08:13:50PM +0300, Serge Semin wrote:
> In general the Synopsys PCIe EndPoint IP prototype kit can be attached to
> a PCIe bus with any PCIe Host controller including to the one with
> distinctive from CPU address space. Due to that we need to make sure that
> the source and destination addresses of the DMA-slave devices are properly
> converted to the PCIe bus address space, otherwise the DMA transaction
> will not only work as expected, but may cause the memory corruption with
> subsequent system crash. Let's do that by introducing a new
> dw_edma_pcie_address() method defined in the dw-edma-pcie.c, which will
> perform the denoted translation by using the pcibios_resource_to_bus()
> method.
> 
> Fixes: 41aaff2a2ac0 ("dmaengine: Add Synopsys eDMA IP PCIe glue-logic")
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Acked-by: Vinod Koul <vkoul@...nel.org>
> 
> ---
> 
> Note this patch depends on the patch "dmaengine: dw-edma: Add CPU to PCIe
> bus address translation" from this series.
> ---
>  drivers/dma/dw-edma/dw-edma-pcie.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c b/drivers/dma/dw-edma/dw-edma-pcie.c
> index 04c95cba1244..f530bacfd716 100644
> --- a/drivers/dma/dw-edma/dw-edma-pcie.c
> +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
> @@ -95,8 +95,23 @@ static int dw_edma_pcie_irq_vector(struct device *dev, unsigned int nr)
>  	return pci_irq_vector(to_pci_dev(dev), nr);
>  }
>  
> +static u64 dw_edma_pcie_address(struct device *dev, phys_addr_t cpu_addr)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	struct pci_bus_region region;
> +	struct resource res = {
> +		.flags = IORESOURCE_MEM,
> +		.start = cpu_addr,
> +		.end = cpu_addr,
> +	};
> +
> +	pcibios_resource_to_bus(pdev->bus, &region, &res);
> +	return region.start;
> +}

This doesn't look DW-specific.  Do you expect other implementations
that are specific, or could this be a generic function that shares
some implementation with pci_bus_address()?

>  static const struct dw_edma_core_ops dw_edma_pcie_core_ops = {
>  	.irq_vector = dw_edma_pcie_irq_vector,
> +	.pci_address = dw_edma_pcie_address,
>  };
>  
>  static void dw_edma_pcie_get_vsec_dma_data(struct pci_dev *pdev,
> -- 
> 2.39.0
> 
>