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

[Zhi Li <lznuaa@gmail.com>]

On Wed, May 11, 2022 at 2:12 PM Zhi Li <lznuaa@gmail.com> wrote:
>
> On Wed, May 11, 2022 at 12:30 PM Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.com> wrote:
> >
> > On Wed, May 11, 2022 at 11:18:20AM -0500, Zhi Li wrote:
> > > On Wed, May 11, 2022 at 4:28 AM Lorenzo Pieralisi
> > > <lorenzo.pieralisi@arm.com> wrote:
> > > >
> > > > [+Kishon]
> > > >
> > > > On Mon, May 02, 2022 at 07:58:01PM -0500, 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.
> > > >
> > > > I am sorry to be pedantic but which DMA controller ?
> > > >
> > > > Do you mean "DMA controllers embedded in Endpoint controllers" ?
> > >
> > > Yes.
> > >
> > > >
> > > > This is a bit vague and overall you are patching pci-epf-test.c,
> > > > that's the change that has to be explained.
> > > >
> > > > If Kishon can have a look that would be greatly appreciated too.
> > > >
> > > > When we agree on a proper commit log I can ACK the patch, the whole
> > > > series can then go via the DMA engine tree.
> > >
> > > How about the below commit message? Is it clear?
> >
> > It is better but I have some suggestions below.
> >
> > > PCI: endpoint: Enable DMA controller tests for endpoints with DMA
> > > capabilities
> >
> > "PCI: endpoint: Enable DMA tests for endpoints with DMA capabilities"
> >
> > > Some PCI Endpoints controllers integrate an eDMA (embedded DMA).
> > > eDMA has more efficiency than a general DMA controller.
> >
> > What does "has more efficiency" means ? You mean it can bypass the
> > memory translation unit ?
>
> Generally Memory to memory DMA work as
>  - DMA read from DDR into DMA controller FIFO,  AXI Read
>  - DMA write to PCI space from DMA controller FIFO, AXI write
>  - PCI EP controller converts AXI write to PCI TLP into PCI bus.
>
> EP eDMA works as
>  - eDMA read from DDR,
>  - Convert PCI TLP into PCI bus.
>
> a AXI write operator saved. so I think efficiency is higher than general DMA.
>
> >
> > > And eDMA can bypass
> >
> > Don't start a sentence with "And".
> >
> > > outbound memory address translation unit to access all RC memory space.
> > >
> > > This patch added eDMA support for pci-epf-test.
> >
> > "Add eDMA support for pci-epf-test".
> >
> > This patch is doing more than this though, doesn't it ?
> >
> > I would write (always use imperative statements):
> >
> > "Add DMA support for pci-epf-test.
> >
> > EPF endpoints can use, depending on HW availability, eDMA or general
> > system DMA controllers to perform DMA.
> >
> > The test probes the EPF DMA channel capabilities."
> >
> > Then you can add the description below.
> >
> > >   - Separate DMA channel to TX and RX. eDMA channels have higher priority than
> > >  general DMA channels.  If general memory to memory DMA channels are used,
> > >  RX and TX channels are equal.
> >
> > What does "are equal" mean ? By the way, please remove double spaces
>
> RX = TX.
>
> > after a period. If you need to start a new paragraph add a new line.
> >
> > >  -  Add dma_addr_t dma_remote in in function
> > > pci_epf_test_data_transfer() because
> > > eDMA using remote RC physical address directly
> > > -  Add enum dma_transfer_direction dir in function
> > > pci_epf_test_data_transfer() because
> > > eDMA chooses the correct RX/TX channel by dir.
> > >
> > > The overall steps are
> > >
> > >  1. Using dma_request_channel() and filter function to find correct
> >
> > s/Using/Execute
> >
> > >     eDMA RX and TX Channel. if channel not exist,  fallback to try allocate
> >
> > "If a channel does not exist"
> >
> > >     general memory to memory DMA  channel.
> > >  2. Using dmaengine_slave_config() config remote side physical address.
> >
> > s/Using/Execute - "to configure remote"
> >
> > >  3. Using dmaengine_prep_slave_single() create transfer descriptor.
> >
> > s/Using/Execute - "to create"
> >
> >
> > >  4. tx_submit();
> >
> > Execute tx_submit()
> >
> > >  5. dma_async_issue_pending();
> >
> > Execute dma_async_issue_pending()
> >
> > Overall, all you need to do describe is what the patch does, hopefully
> > the comments above can help.
>
> Updated commit message:
>
> PCI: endpoint: Enable DMA tests for endpoints with DMA capabilities
>
> Some PCI Endpoints controllers integrate an eDMA (embedded DMA).
> eDMA only sends once a bus read/write command to complete once
> data transfer. eDMA can bypass the outbound memory address translation
> unit to access all RC memory space.
>
> Add DMA support for pci-epf-test.
>
> EPF test can use, depending on HW availability, eDMA or general system DMA
> controllers to perform DMA. The test probes the EPF DMA channel capabilities.
>
> Separate dma_chan to dma_chan_tx and dma_chan_rx. eDMA channels have
> higher priority than general DMA channels. If general memory to memory DMA
> hannels are used, dma_chan_rx = dma_chan_tx.
>
> Add dma_addr_t dma_remote in in function pci_epf_test_data_transfer() because
> eDMA using remote RC physical address directly
>
> Add enum dma_transfer_direction dir in function pci_epf_test_data_transfer()
> because eDMA chooses the correct RX/TX channel by dir.
>
> The overall steps are
>
> 1. Execute dma_request_channel() and filter function to find correct eDMA
> RX and TX Channel. If a channel does not exist,  fallback to try to allocate
> general memory to memory DMA  channel.
> 2. Execute dmaengine_slave_config() to configure remote side physical address.
> 3. Execute dmaengine_prep_slave_single() to create transfer descriptor.
> 4. Execute tx_submit().
> 5. Execute  dma_async_issue_pending()
>

@Lorenzo Pieralisi  Are you satisfied with the above comment message?
There are some big patch series depending on this patch series.

>
>
>
> >
> > Thanks,
> > Lorenzo
> >
> > > > Thanks,
> > > > Lorenzo
> > > >
> > > > >
> > > > > 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>
> > > > > ---
> > > > > 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
> > > > >