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

From: Zhi Li <lznuaa@gmail.com>
To: Kishon Vijay Abraham I <kishon@ti.com>
Cc: "Frank Li" <Frank.Li@nxp.com>,
	"Gustavo Pimentel" <gustavo.pimentel@synopsys.com>,
	hongxing.zhu@nxp.com, "Lucas Stach" <l.stach@pengutronix.de>,
	dl-linux-imx <linux-imx@nxp.com>,
	linux-pci@vger.kernel.org, dmaengine@vger.kernel.org,
	"Serge Semin" <fancer.lancer@gmail.com>,
	"Bjorn Helgaas" <helgaas@kernel.org>,
	"Vinod Koul" <vkoul@kernel.org>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
	"Serge Semin" <Sergey.Semin@baikalelectronics.ru>
Subject: Re: [PATCH v10 9/9] PCI: endpoint: Enable DMA controller tests for endpoints with DMA capabilities
Date: Thu, 12 May 2022 10:36:47 -0500	[thread overview]
Message-ID: <CAHrpEqT4hZ3G1YBxYdjHVDrPGZoZEpd_C==yK+CNE-ZOtk2nCA@mail.gmail.com> (raw)
In-Reply-To: <b2961b3e-ad0e-5b8f-8d6f-221aead9992f@ti.com>

On Thu, May 12, 2022 at 8:52 AM Kishon Vijay Abraham I <kishon@ti.com> wrote:
>
> Hi Frank,
>
> On 03/05/22 06:28, Frank Li 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>
>
> The patch looks good to me (other than Lorenzo's comment on the
> description). Did you also verify DMA_MEMCPY just to make sure, the old
> path continues to work?

Not yet, our hardware platform has not memory to memory DMA.

best regards
Frank Li

>
> Regards,
> Kishon
> > ---
> > 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);