Re: [RFC PATCH 2/5] PCI: endpoint: Add support to data transfer using internal dmac

[Manivannan Sadhasivam]

On Wed, Jan 26, 2022 at 07:50:40PM +0000, Lad Prabhakar wrote:
> For PCIe EP capable with internal DMAC, transfer data using this
> when -d option is used with pcitest.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 184 ++++++++++++++----
>  1 file changed, 141 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 90d84d3bc868..f792b1a15c44 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -55,6 +55,7 @@ struct pci_epf_test {
>  	struct dma_chan		*dma_chan;
>  	struct completion	transfer_complete;
>  	bool			dma_supported;
> +	bool			internal_dmac;

Please use "dma" everywhere.

>  	const struct pci_epc_features *epc_features;
>  };
>  
> @@ -148,6 +149,40 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
>  	return 0;
>  }
>  
> +/**
> + * pci_epf_test_internal_dmac_data_transfer() - Function that uses internal DMAC
> + *				to transfer data between PCIe EP and remote PCIe RC
> + * @epf_test: the EPF test device that performs the data transfer operation
> + * @dma_dst: The destination address of the data transfer. It can be a physical
> + *	     address given by pci_epc_mem_alloc_addr or DMA mapping APIs.
> + * @dma_src: The source address of the data transfer. It can be a physical
> + *	     address given by pci_epc_mem_alloc_addr or DMA mapping APIs.
> + * @len: The size of the data transfer
> + * @dir: Direction of data transfer
> + *
> + * Function that uses internal dmac supported by the controller to transfer data
> + * between PCIe EP and remote PCIe RC.
> + *
> + * The function returns '0' on success and negative value on failure.
> + */
> +static int
> +pci_epf_test_internal_dmac_data_transfer(struct pci_epf_test *epf_test,
> +					 dma_addr_t dma_dst, dma_addr_t dma_src,
> +					 size_t len, enum pci_epf_xfr_direction dir)
> +{
> +	struct pci_epf *epf = epf_test->epf;
> +	int ret;
> +
> +	if (!epf_test->internal_dmac)
> +		return -EINVAL;
> +
> +	ret = pci_epf_internal_dmac_xfr(epf, dma_dst, dma_src, len, dir);
> +	if (ret)
> +		return -EIO;

Why can't you return "ret"?

> +
> +	return 0;
> +}
> +
>  /**
>   * pci_epf_test_init_dma_chan() - Function to initialize EPF test DMA channel
>   * @epf_test: the EPF test device that performs data transfer operation
> @@ -238,6 +273,14 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)
>  	struct pci_epc *epc = epf->epc;
>  	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
>  	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
> +	bool internal_dmac = epf_test->internal_dmac;
> +
> +	use_dma = !!(reg->flags & FLAG_USE_DMA);
> +
> +	if (use_dma && internal_dmac) {
> +		dev_err(dev, "Operation not supported\n");

Here you are erroring out but below you are checking for this condition to do
internal DMA transfer.

> +		return -EINVAL;
> +	}
>  
>  	src_addr = pci_epc_mem_alloc_addr(epc, &src_phys_addr, reg->size);
>  	if (!src_addr) {
> @@ -272,7 +315,6 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)

Why internal DMA is not used in pci_epf_test_copy()?

>  	}
>  
>  	ktime_get_ts64(&start);
> -	use_dma = !!(reg->flags & FLAG_USE_DMA);
>  	if (use_dma) {
>  		if (!epf_test->dma_supported) {
>  			dev_err(dev, "Cannot transfer data using DMA\n");
> @@ -322,31 +364,49 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
>  	struct device *dma_dev = epf->epc->dev.parent;
>  	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
>  	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
> +	bool internal_dmac = epf_test->internal_dmac;
>  
> -	src_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
> -	if (!src_addr) {
> -		dev_err(dev, "Failed to allocate address\n");
> -		reg->status = STATUS_SRC_ADDR_INVALID;
> -		ret = -ENOMEM;
> -		goto err;
> -	}
> +	use_dma = !!(reg->flags & FLAG_USE_DMA);
>  
> -	ret = pci_epc_map_addr(epc, epf->func_no, epf->vfunc_no, phys_addr,
> -			       reg->src_addr, reg->size);
> -	if (ret) {
> -		dev_err(dev, "Failed to map address\n");
> -		reg->status = STATUS_SRC_ADDR_INVALID;
> -		goto err_addr;
> +	if (use_dma && internal_dmac) {

Both are mutually exclusive, isn't it?

> +		phys_addr = reg->src_addr;
> +		src_addr = NULL;
> +	} else {
> +		src_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
> +		if (!src_addr) {
> +			dev_err(dev, "Failed to allocate address\n");
> +			reg->status = STATUS_SRC_ADDR_INVALID;
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		ret = pci_epc_map_addr(epc, epf->func_no, epf->vfunc_no, phys_addr,
> +				       reg->src_addr, reg->size);
> +		if (ret) {
> +			dev_err(dev, "Failed to map address\n");
> +			reg->status = STATUS_SRC_ADDR_INVALID;
> +			goto err_addr;
> +		}
>  	}
>  

[...]

>  
>  	ret = pci_epf_test_alloc_space(epf);
>  	if (ret)
> @@ -868,11 +964,13 @@ static int pci_epf_test_bind(struct pci_epf *epf)
>  			return ret;
>  	}
>  
> -	epf_test->dma_supported = true;
> +	epf_test->dma_supported = false;
>  
> -	ret = pci_epf_test_init_dma_chan(epf_test);
> -	if (ret)
> -		epf_test->dma_supported = false;
> +	if (!epf_test->internal_dmac) {
> +		ret = pci_epf_test_init_dma_chan(epf_test);
> +		if (!ret)
> +			epf_test->dma_supported = true;

You can set this flag to true inside pci_epf_test_init_dma_chan().

Thanks,
Mani

> +	}
>  
>  	if (linkup_notifier) {
>  		epf->nb.notifier_call = pci_epf_test_notifier;
> -- 
> 2.25.1
>