linux-kernel - Re: [PATCH 05/25] dmaengine: dw-edma: Convert ll/dt phys-address to PCIe bus/DMA address

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Message-ID: <20220324162304.GO2854@thinkpad>
Date:   Thu, 24 Mar 2022 21:53:04 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Frank Li <Frank.Li@....com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/25] dmaengine: dw-edma: Convert ll/dt phys-address to
 PCIe bus/DMA address

On Thu, Mar 24, 2022 at 04:48:16AM +0300, Serge Semin wrote:
> In accordance with the dw_edma_region.paddr field semantics it is supposed
> to be initialized with a memory base address visible by the DW eDMA
> controller. If the DMA engine is embedded into the DW PCIe Host/EP
> controller, then the address should belong to the Local CPU/Application
> memory. If eDMA is remotely accessible across the PCIe bus via the PCIe
> memory IOs, then the address needs to be a part of the PCIe bus memory
> space. The later case hasn't been well covered in the corresponding
> glue-driver. Since in general the PCIe memory space doesn't have to match
> the CPU memory space and the pci_dev.resource[] arrays contain the
> resources defined in the CPU memory space, a proper conversion needs to be
> performed, otherwise either the driver won't properly work or much worse
> the memory corruption will happen. The conversion can be done by means of
> the pci_bus_address() method. Let's use it to retrieve the LL, DT and CSRs
> PCIe memory ranges.
> 
> Note in addition to that we need to extend the dw_edma_region.paddr field
> size. The field normally contains a memory range base address to be set in
> the DW eDMA Linked-List pointer register or as a base address of the
> Linked-List data buffer. In accordance with [1] the LL range is supposed
> to be created in the Local CPU/Application memory, but depending on the DW
> eDMA utilization the memory can be created as a part of the PCIe bus
> address space (as in the case of the DW PCIe EP prototype kit). Thus in
> the former case the dw_edma_region.paddr field should have the dma_addr_t
> type, while in the later one - pci_bus_addr_t. Seeing the corresponding
> CSRs are always 64-bits wide let's convert the dw_edma_region.paddr field
> type to be u64 and let the client code logic to make sure it has a valid
> address visible by the DW eDMA controller. For instance the DW eDMA PCIe
> glue-driver initializes the field with the addresses from the PCIe bus
> memory space.
> 
> [1] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
>     v.5.40a, March 2019, p.1103
> 
> 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>

Thanks,
Mani

> ---
>  drivers/dma/dw-edma/dw-edma-pcie.c | 8 ++++----
>  include/linux/dma/edma.h           | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c b/drivers/dma/dw-edma/dw-edma-pcie.c
> index d6b5e2463884..04c95cba1244 100644
> --- a/drivers/dma/dw-edma/dw-edma-pcie.c
> +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
> @@ -231,7 +231,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
>  			return -ENOMEM;
>  
>  		ll_region->vaddr += ll_block->off;
> -		ll_region->paddr = pdev->resource[ll_block->bar].start;
> +		ll_region->paddr = pci_bus_address(pdev, ll_block->bar);
>  		ll_region->paddr += ll_block->off;
>  		ll_region->sz = ll_block->sz;
>  
> @@ -240,7 +240,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
>  			return -ENOMEM;
>  
>  		dt_region->vaddr += dt_block->off;
> -		dt_region->paddr = pdev->resource[dt_block->bar].start;
> +		dt_region->paddr = pci_bus_address(pdev, dt_block->bar);
>  		dt_region->paddr += dt_block->off;
>  		dt_region->sz = dt_block->sz;
>  	}
> @@ -256,7 +256,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
>  			return -ENOMEM;
>  
>  		ll_region->vaddr += ll_block->off;
> -		ll_region->paddr = pdev->resource[ll_block->bar].start;
> +		ll_region->paddr = pci_bus_address(pdev, ll_block->bar);
>  		ll_region->paddr += ll_block->off;
>  		ll_region->sz = ll_block->sz;
>  
> @@ -265,7 +265,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
>  			return -ENOMEM;
>  
>  		dt_region->vaddr += dt_block->off;
> -		dt_region->paddr = pdev->resource[dt_block->bar].start;
> +		dt_region->paddr = pci_bus_address(pdev, dt_block->bar);
>  		dt_region->paddr += dt_block->off;
>  		dt_region->sz = dt_block->sz;
>  	}
> diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> index 8897f8a79b52..5abac9640a4e 100644
> --- a/include/linux/dma/edma.h
> +++ b/include/linux/dma/edma.h
> @@ -18,7 +18,7 @@
>  struct dw_edma;
>  
>  struct dw_edma_region {
> -	phys_addr_t	paddr;
> +	u64		paddr;
>  	void __iomem	*vaddr;
>  	size_t		sz;
>  };
> -- 
> 2.35.1
>