On Mon, May 23, 2022 at 1:22 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> On Tue, May 17, 2022 at 10:19:15AM -0500, Frank Li wrote:
> > 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.
>
> s/Endpoints/Endpoint/
>
> I'm not sure what "only sends once a command to complete once
> transfer" means or why it is revelant here. I guess it just means
> "the eDMA controller issues a single bus command per data transfer"?
>
> > Add DMA support for pci-epf-test.
>
> It looks like pci-epf-test.c already *has* DMA support, but you're
> adding support for separate RX and TX DMA channels.
pci-epf-test already has memory to memory DMA support.
I added eDMA support.
>
> > 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.
>
> I think the "priority" you refer to is merely that the *test* uses
> eDMA channels if present, not that there's any actual hardware
> priority involved here, right?
Yes, choose EDMA channel first if it exists, then choose memory to
memory dma channel.
>
> > If general memory to memory
> > DMA hannels are used, dma_chan_rx = dma_chan_tx.
>
> s/hannels/channels/
>
> > Add dma_addr_t dma_remote in function pci_epf_test_data_transfer()
> > because eDMA using remote RC physical address directly
>
> s/function pci_epf_test_data_transfer()/pci_epf_test_data_transfer()/
> s/eDMA using/eDMA uses/
> s/directly/directly./
>
> (No need to specify "function" since the parens make it obvious that
> pci_epf_test_data_transfer() is a function. Same thing below.)
>
> > 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.
>
> s/exist, /exist, / remove extra space
> s/memory DMA /memory DMA / remove extra space again
>
> > 2. Execute dmaengine_slave_config() to configure remote side physical address.
>
> Rewrap to fit in 75 columns.
>
> > 3. Execute dmaengine_prep_slave_single() to create transfer descriptor.
> > 4. Execute tx_submit().
> > 5. Execute dma_async_issue_pending()
> >
> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> > ---
Bjorn: Are you satisfied with the below message? I will fix the
other code in the next version.
Some PCI Endpoint controllers integrate an eDMA (embedded DMA).
The eDMA controller issues a single bus command per data transfer.
eDMA can bypass the outbound memory address translation unit to
access all RC memory space.
Add eDMA 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. Search eDMA channel
firstly, then search memory to memory DMA channel if eDMA does not exist.
If general memory to memory channels are used, dma_chan_rx = dma_chan_tx.
Add dma_addr_t dma_remote in pci_epf_test_data_transfer()
because eDMA uses remote RC physical address directly.
Add enum dma_transfer_direction dir in 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()
> > Change from v10 to v11:
> > - rewrite commit message
> > 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)
>
> Please update the kernel-doc for these two new parameters. You can
> use:
>
> $ make W=1 drivers/pci/endpoint/functions/
>
> to find errors like this.
>
> > {
> > + 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");
>
> These messages should indicate whether the failure was for the
> DEV_TO_MEM channel or the MEM_TO_DEV channel. Otherwise the failure
> looks the same to the user.
>
> > + 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);
>
> Wrap to fit in 80 columns, like the rest of the file. There are a
> couple other cases above (the dev_info() cases are fine since we don't
> want to split info/error message strings).
>
> > if (ret)
> > dev_err(dev, "Data transfer failed\n");
> > ktime_get_ts64(&end);
> > --
> > 2.35.1
> >
