Re: [PATCH v10 9/9] PCI: endpoint: Enable DMA controller tests for endpoints with DMA capabilities

[Zhi Li <lznuaa@gmail.com>]

On Mon, May 2, 2022 at 7:59 PM Frank Li <Frank.Li@nxp.com> wrote:
>
> Some Endpoints controllers have DMA capabilities.  This DMA controller has
> more efficiency then a general external DMA controller.  And this DMA
> controller can bypass outbound memory address translation unit.
>
> The whole flow use standard DMA usage module
>
>  1. Using dma_request_channel() and filter function to find correct
>     RX and TX Channel. if not exist,  fallback to try allocate
>     general DMA controller channel.
>  2. dmaengine_slave_config() config remote side physcial address.
>  3. using dmaengine_prep_slave_single() create transfer descriptor.
>  4. tx_submit();
>  5. dma_async_issue_pending();
>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Added kishon@ti.com

best regards
Frank Li

> ---
> Change from v9 to v10:
>  - rewrite commit message
> Change from v4 to v9:
>  - none
> Change from v3 to v4:
>  - reverse Xmas tree order
>  - local -> dma_local
>  - change error message
>  - IS_ERR -> IS_ERR_OR_NULL
>  - check return value of dmaengine_slave_config()
> Change from v1 to v2:
>  - none
>
>  drivers/pci/endpoint/functions/pci-epf-test.c | 108 ++++++++++++++++--
>  1 file changed, 98 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 90d84d3bc868f..f26afd02f3a86 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -52,9 +52,11 @@ struct pci_epf_test {
>         enum pci_barno          test_reg_bar;
>         size_t                  msix_table_offset;
>         struct delayed_work     cmd_handler;
> -       struct dma_chan         *dma_chan;
> +       struct dma_chan         *dma_chan_tx;
> +       struct dma_chan         *dma_chan_rx;
>         struct completion       transfer_complete;
>         bool                    dma_supported;
> +       bool                    dma_private;
>         const struct pci_epc_features *epc_features;
>  };
>
> @@ -105,12 +107,15 @@ static void pci_epf_test_dma_callback(void *param)
>   */
>  static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
>                                       dma_addr_t dma_dst, dma_addr_t dma_src,
> -                                     size_t len)
> +                                     size_t len, dma_addr_t dma_remote,
> +                                     enum dma_transfer_direction dir)
>  {
> +       struct dma_chan *chan = (dir == DMA_DEV_TO_MEM) ? epf_test->dma_chan_tx : epf_test->dma_chan_rx;
> +       dma_addr_t dma_local = (dir == DMA_MEM_TO_DEV) ? dma_src : dma_dst;
>         enum dma_ctrl_flags flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
> -       struct dma_chan *chan = epf_test->dma_chan;
>         struct pci_epf *epf = epf_test->epf;
>         struct dma_async_tx_descriptor *tx;
> +       struct dma_slave_config sconf = {};
>         struct device *dev = &epf->dev;
>         dma_cookie_t cookie;
>         int ret;
> @@ -120,7 +125,22 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
>                 return -EINVAL;
>         }
>
> -       tx = dmaengine_prep_dma_memcpy(chan, dma_dst, dma_src, len, flags);
> +       if (epf_test->dma_private) {
> +               sconf.direction = dir;
> +               if (dir == DMA_MEM_TO_DEV)
> +                       sconf.dst_addr = dma_remote;
> +               else
> +                       sconf.src_addr = dma_remote;
> +
> +               if (dmaengine_slave_config(chan, &sconf)) {
> +                       dev_err(dev, "DMA slave config fail\n");
> +                       return -EIO;
> +               }
> +               tx = dmaengine_prep_slave_single(chan, dma_local, len, dir, flags);
> +       } else {
> +               tx = dmaengine_prep_dma_memcpy(chan, dma_dst, dma_src, len, flags);
> +       }
> +
>         if (!tx) {
>                 dev_err(dev, "Failed to prepare DMA memcpy\n");
>                 return -EIO;
> @@ -148,6 +168,23 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
>         return 0;
>  }
>
> +struct epf_dma_filter {
> +       struct device *dev;
> +       u32 dma_mask;
> +};
> +
> +static bool epf_dma_filter_fn(struct dma_chan *chan, void *node)
> +{
> +       struct epf_dma_filter *filter = node;
> +       struct dma_slave_caps caps;
> +
> +       memset(&caps, 0, sizeof(caps));
> +       dma_get_slave_caps(chan, &caps);
> +
> +       return chan->device->dev == filter->dev
> +               && (filter->dma_mask & caps.directions);
> +}
> +
>  /**
>   * pci_epf_test_init_dma_chan() - Function to initialize EPF test DMA channel
>   * @epf_test: the EPF test device that performs data transfer operation
> @@ -158,10 +195,44 @@ static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
>  {
>         struct pci_epf *epf = epf_test->epf;
>         struct device *dev = &epf->dev;
> +       struct epf_dma_filter filter;
>         struct dma_chan *dma_chan;
>         dma_cap_mask_t mask;
>         int ret;
>
> +       filter.dev = epf->epc->dev.parent;
> +       filter.dma_mask = BIT(DMA_DEV_TO_MEM);
> +
> +       dma_cap_zero(mask);
> +       dma_cap_set(DMA_SLAVE, mask);
> +       dma_chan = dma_request_channel(mask, epf_dma_filter_fn, &filter);
> +       if (IS_ERR_OR_NULL(dma_chan)) {
> +               dev_info(dev, "Failed to get private DMA channel. Falling back to generic one\n");
> +               goto fail_back_tx;
> +       }
> +
> +       epf_test->dma_chan_rx = dma_chan;
> +
> +       filter.dma_mask = BIT(DMA_MEM_TO_DEV);
> +       dma_chan = dma_request_channel(mask, epf_dma_filter_fn, &filter);
> +
> +       if (IS_ERR(dma_chan)) {
> +               dev_info(dev, "Failed to get private DMA channel. Falling back to generic one\n");
> +               goto fail_back_rx;
> +       }
> +
> +       epf_test->dma_chan_tx = dma_chan;
> +       epf_test->dma_private = true;
> +
> +       init_completion(&epf_test->transfer_complete);
> +
> +       return 0;
> +
> +fail_back_rx:
> +       dma_release_channel(epf_test->dma_chan_rx);
> +       epf_test->dma_chan_tx = NULL;
> +
> +fail_back_tx:
>         dma_cap_zero(mask);
>         dma_cap_set(DMA_MEMCPY, mask);
>
> @@ -174,7 +245,7 @@ static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
>         }
>         init_completion(&epf_test->transfer_complete);
>
> -       epf_test->dma_chan = dma_chan;
> +       epf_test->dma_chan_tx = epf_test->dma_chan_rx = dma_chan;
>
>         return 0;
>  }
> @@ -190,8 +261,17 @@ static void pci_epf_test_clean_dma_chan(struct pci_epf_test *epf_test)
>         if (!epf_test->dma_supported)
>                 return;
>
> -       dma_release_channel(epf_test->dma_chan);
> -       epf_test->dma_chan = NULL;
> +       dma_release_channel(epf_test->dma_chan_tx);
> +       if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
> +               epf_test->dma_chan_tx = NULL;
> +               epf_test->dma_chan_rx = NULL;
> +               return;
> +       }
> +
> +       dma_release_channel(epf_test->dma_chan_rx);
> +       epf_test->dma_chan_rx = NULL;
> +
> +       return;
>  }
>
>  static void pci_epf_test_print_rate(const char *ops, u64 size,
> @@ -280,8 +360,14 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)
>                         goto err_map_addr;
>                 }
>
> +               if (epf_test->dma_private) {
> +                       dev_err(dev, "Cannot transfer data using DMA\n");
> +                       ret = -EINVAL;
> +                       goto err_map_addr;
> +               }
> +
>                 ret = pci_epf_test_data_transfer(epf_test, dst_phys_addr,
> -                                                src_phys_addr, reg->size);
> +                                                src_phys_addr, reg->size, 0, DMA_MEM_TO_MEM);
>                 if (ret)
>                         dev_err(dev, "Data transfer failed\n");
>         } else {
> @@ -363,7 +449,8 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
>
>                 ktime_get_ts64(&start);
>                 ret = pci_epf_test_data_transfer(epf_test, dst_phys_addr,
> -                                                phys_addr, reg->size);
> +                                                phys_addr, reg->size,
> +                                                reg->src_addr, DMA_DEV_TO_MEM);
>                 if (ret)
>                         dev_err(dev, "Data transfer failed\n");
>                 ktime_get_ts64(&end);
> @@ -453,8 +540,9 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test)
>                 }
>
>                 ktime_get_ts64(&start);
> +
>                 ret = pci_epf_test_data_transfer(epf_test, phys_addr,
> -                                                src_phys_addr, reg->size);
> +                                                src_phys_addr, reg->size, reg->dst_addr, DMA_MEM_TO_DEV);
>                 if (ret)
>                         dev_err(dev, "Data transfer failed\n");
>                 ktime_get_ts64(&end);
> --
> 2.35.1
>