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Message-ID:
<SA1PR12MB81204151B77CA7048E0D793595FAA@SA1PR12MB8120.namprd12.prod.outlook.com>
Date: Wed, 29 Oct 2025 08:35:12 +0000
From: "Verma, Devendra" <Devendra.Verma@....com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC: "bhelgaas@...gle.com" <bhelgaas@...gle.com>, "mani@...nel.org"
<mani@...nel.org>, "vkoul@...nel.org" <vkoul@...nel.org>,
"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, LKML
<linux-kernel@...r.kernel.org>, "Simek, Michal" <michal.simek@....com>,
"Verma, Devendra" <Devendra.Verma@....com>
Subject: RE: [PATCH v5 2/2] dmaengine: dw-edma: Add non-LL mode
[AMD Official Use Only - AMD Internal Distribution Only]
Thank you @Ilpo Järvinen for the inputs.
Please check my response inline.
Regards,
Devendra
> -----Original Message-----
> From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Sent: Tuesday, October 28, 2025 7:03 PM
> To: Verma, Devendra <Devendra.Verma@....com>
> Cc: bhelgaas@...gle.com; mani@...nel.org; vkoul@...nel.org;
> dmaengine@...r.kernel.org; linux-pci@...r.kernel.org; LKML <linux-
> kernel@...r.kernel.org>; Simek, Michal <michal.simek@....com>
> Subject: Re: [PATCH v5 2/2] dmaengine: dw-edma: Add non-LL mode
>
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
>
>
> On Tue, 28 Oct 2025, Devendra K Verma wrote:
>
> > AMD MDB IP supports Linked List (LL) mode as well as non-LL mode.
> > The current code does not have the mechanisms to enable the DMA
> > transactions using the non-LL mode. The following two cases are added
> > with this patch:
> > - When a valid physical base address is not configured via the
> > Xilinx VSEC capability then the IP can still be used in non-LL
> > mode. The default mode for all the DMA transactions and for all
> > the DMA channels then is non-LL mode.
> > - When a valid physical base address is configured but the client
> > wants to use the non-LL mode for DMA transactions then also the
> > flexibility is provided via the peripheral_config struct member of
> > dma_slave_config. In this case the channels can be individually
> > configured in non-LL mode. This use case is desirable for single
> > DMA transfer of a chunk, this saves the effort of preparing the
> > Link List. This particular scenario is applicable to AMD as well
> > as Synopsys IP.
> >
> > Signed-off-by: Devendra K Verma <devendra.verma@....com>
> > ---
> > Changes in v5
> > Variable name 'nollp' changed to 'non_ll'.
> > In the dw_edma_device_config() WARN_ON replaced with dev_err().
> > Comments follow the 80-column guideline.
> >
> > Changes in v4
> > No change
> >
> > Changes in v3
> > No change
> >
> > Changes in v2
> > Reverted the function return type to u64 for
> > dw_edma_get_phys_addr().
> >
> > Changes in v1
> > Changed the function return type for dw_edma_get_phys_addr().
> > Corrected the typo raised in review.
> > ---
> > drivers/dma/dw-edma/dw-edma-core.c | 41 ++++++++++++++++++++---
> > drivers/dma/dw-edma/dw-edma-core.h | 1 +
> > drivers/dma/dw-edma/dw-edma-pcie.c | 44 +++++++++++++++++--------
> > drivers/dma/dw-edma/dw-hdma-v0-core.c | 62
> ++++++++++++++++++++++++++++++++++-
> > include/linux/dma/edma.h | 1 +
> > 5 files changed, 130 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/dma/dw-edma/dw-edma-core.c
> > b/drivers/dma/dw-edma/dw-edma-core.c
> > index b43255f..60a3279 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > @@ -223,8 +223,31 @@ static int dw_edma_device_config(struct
> dma_chan *dchan,
> > struct dma_slave_config *config) {
> > struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> > + int non_ll = 0;
> > +
> > + if (config->peripheral_config &&
> > + config->peripheral_size != sizeof(int)) {
> > + dev_err(dchan->device->dev,
> > + "config param peripheral size mismatch\n");
> > + return -EINVAL;
> > + }
> >
> > memcpy(&chan->config, config, sizeof(*config));
> > +
> > + /*
> > + * When there is no valid LLP base address available then the default
> > + * DMA ops will use the non-LL mode.
> > + * Cases where LL mode is enabled and client wants to use the non-LL
> > + * mode then also client can do so via providing the peripheral_config
> > + * param.
> > + */
> > + if (config->peripheral_config)
> > + non_ll = *(int *)config->peripheral_config;
> > +
> > + chan->non_ll = false;
> > + if (chan->dw->chip->non_ll || (!chan->dw->chip->non_ll && non_ll))
> > + chan->non_ll = true;
> > +
> > chan->configured = true;
> >
> > return 0;
> > @@ -353,7 +376,7 @@ static void dw_edma_device_issue_pending(struct
> dma_chan *dchan)
> > struct dw_edma_chan *chan = dchan2dw_edma_chan(xfer->dchan);
> > enum dma_transfer_direction dir = xfer->direction;
> > struct scatterlist *sg = NULL;
> > - struct dw_edma_chunk *chunk;
> > + struct dw_edma_chunk *chunk = NULL;
> > struct dw_edma_burst *burst;
> > struct dw_edma_desc *desc;
> > u64 src_addr, dst_addr;
> > @@ -419,9 +442,11 @@ static void dw_edma_device_issue_pending(struct
> dma_chan *dchan)
> > if (unlikely(!desc))
> > goto err_alloc;
> >
> > - chunk = dw_edma_alloc_chunk(desc);
> > - if (unlikely(!chunk))
> > - goto err_alloc;
> > + if (!chan->non_ll) {
> > + chunk = dw_edma_alloc_chunk(desc);
> > + if (unlikely(!chunk))
> > + goto err_alloc;
> > + }
> >
> > if (xfer->type == EDMA_XFER_INTERLEAVED) {
> > src_addr = xfer->xfer.il->src_start; @@ -450,7 +475,13
> > @@ static void dw_edma_device_issue_pending(struct dma_chan *dchan)
> > if (xfer->type == EDMA_XFER_SCATTER_GATHER && !sg)
> > break;
> >
> > - if (chunk->bursts_alloc == chan->ll_max) {
> > + /*
> > + * For non-LL mode, only a single burst can be handled
> > + * in a single chunk unlike LL mode where multiple bursts
> > + * can be configured in a single chunk.
> > + */
> > + if ((chunk && chunk->bursts_alloc == chan->ll_max) ||
> > + chan->non_ll) {
> > chunk = dw_edma_alloc_chunk(desc);
> > if (unlikely(!chunk))
> > goto err_alloc; diff --git
> > a/drivers/dma/dw-edma/dw-edma-core.h
> > b/drivers/dma/dw-edma/dw-edma-core.h
> > index 71894b9..c8e3d19 100644
> > --- a/drivers/dma/dw-edma/dw-edma-core.h
> > +++ b/drivers/dma/dw-edma/dw-edma-core.h
> > @@ -86,6 +86,7 @@ struct dw_edma_chan {
> > u8 configured;
> >
> > struct dma_slave_config config;
> > + bool non_ll;
> > };
> >
> > struct dw_edma_irq {
> > diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c
> > b/drivers/dma/dw-edma/dw-edma-pcie.c
> > index 7b991a0..b02977c 100644
> > --- a/drivers/dma/dw-edma/dw-edma-pcie.c
> > +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
> > @@ -268,6 +268,15 @@ static void
> dw_edma_pcie_get_vsec_dma_data(struct pci_dev *pdev,
> > pdata->devmem_phys_off = off;
> > }
> >
> > +static u64 dw_edma_get_phys_addr(struct pci_dev *pdev,
> > + struct dw_edma_pcie_data *pdata,
> > + enum pci_barno bar) {
> > + if (pdev->vendor == PCI_VENDOR_ID_XILINX)
> > + return pdata->devmem_phys_off;
> > + return pci_bus_address(pdev, bar); }
> > +
> > static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > const struct pci_device_id *pid) { @@
> > -277,6 +286,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > struct dw_edma_chip *chip;
> > int err, nr_irqs;
> > int i, mask;
> > + bool non_ll = false;
> >
> > vsec_data = kmalloc(sizeof(*vsec_data), GFP_KERNEL);
> > if (!vsec_data)
> > @@ -301,21 +311,24 @@ static int dw_edma_pcie_probe(struct pci_dev
> *pdev,
> > if (pdev->vendor == PCI_VENDOR_ID_XILINX) {
> > /*
> > * There is no valid address found for the LL memory
> > - * space on the device side.
> > + * space on the device side. In the absence of LL base
> > + * address use the non-LL mode or simple mode supported by
> > + * the HDMA IP.
> > */
> > if (vsec_data->devmem_phys_off ==
> DW_PCIE_AMD_MDB_INVALID_ADDR)
> > - return -ENOMEM;
> > + non_ll = true;
> >
> > /*
> > * Configure the channel LL and data blocks if number of
> > * channels enabled in VSEC capability are more than the
> > * channels configured in amd_mdb_data.
> > */
> > - dw_edma_set_chan_region_offset(vsec_data, BAR_2, 0,
> > - DW_PCIE_XILINX_LL_OFF_GAP,
> > - DW_PCIE_XILINX_LL_SIZE,
> > - DW_PCIE_XILINX_DT_OFF_GAP,
> > - DW_PCIE_XILINX_DT_SIZE);
> > + if (!non_ll)
> > + dw_edma_set_chan_region_offset(vsec_data, BAR_2, 0,
> > + DW_PCIE_XILINX_LL_OFF_GAP,
> > + DW_PCIE_XILINX_LL_SIZE,
> > + DW_PCIE_XILINX_DT_OFF_GAP,
> > +
> > + DW_PCIE_XILINX_DT_SIZE);
> > }
> >
> > /* Mapping PCI BAR regions */
> > @@ -363,6 +376,7 @@ static int dw_edma_pcie_probe(struct pci_dev
> *pdev,
> > chip->mf = vsec_data->mf;
> > chip->nr_irqs = nr_irqs;
> > chip->ops = &dw_edma_pcie_plat_ops;
> > + chip->non_ll = non_ll;
> >
> > chip->ll_wr_cnt = vsec_data->wr_ch_cnt;
> > chip->ll_rd_cnt = vsec_data->rd_ch_cnt; @@ -371,7 +385,7 @@
> > static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > if (!chip->reg_base)
> > return -ENOMEM;
> >
> > - for (i = 0; i < chip->ll_wr_cnt; i++) {
> > + for (i = 0; i < chip->ll_wr_cnt && !non_ll; i++) {
> > struct dw_edma_region *ll_region = &chip->ll_region_wr[i];
> > struct dw_edma_region *dt_region = &chip->dt_region_wr[i];
> > struct dw_edma_block *ll_block = &vsec_data->ll_wr[i];
> > @@ -382,7 +396,8 @@ static int dw_edma_pcie_probe(struct pci_dev
> *pdev,
> > return -ENOMEM;
> >
> > ll_region->vaddr.io += ll_block->off;
> > - ll_region->paddr = pci_bus_address(pdev, ll_block->bar);
> > + ll_region->paddr = dw_edma_get_phys_addr(pdev, vsec_data,
> > + ll_block->bar);
> > ll_region->paddr += ll_block->off;
> > ll_region->sz = ll_block->sz;
> >
> > @@ -391,12 +406,13 @@ static int dw_edma_pcie_probe(struct pci_dev
> *pdev,
> > return -ENOMEM;
> >
> > dt_region->vaddr.io += dt_block->off;
> > - dt_region->paddr = pci_bus_address(pdev, dt_block->bar);
> > + dt_region->paddr = dw_edma_get_phys_addr(pdev, vsec_data,
> > + dt_block->bar);
> > dt_region->paddr += dt_block->off;
> > dt_region->sz = dt_block->sz;
> > }
> >
> > - for (i = 0; i < chip->ll_rd_cnt; i++) {
> > + for (i = 0; i < chip->ll_rd_cnt && !non_ll; i++) {
> > struct dw_edma_region *ll_region = &chip->ll_region_rd[i];
> > struct dw_edma_region *dt_region = &chip->dt_region_rd[i];
> > struct dw_edma_block *ll_block = &vsec_data->ll_rd[i];
> > @@ -407,7 +423,8 @@ static int dw_edma_pcie_probe(struct pci_dev
> *pdev,
> > return -ENOMEM;
> >
> > ll_region->vaddr.io += ll_block->off;
> > - ll_region->paddr = pci_bus_address(pdev, ll_block->bar);
> > + ll_region->paddr = dw_edma_get_phys_addr(pdev, vsec_data,
> > + ll_block->bar);
> > ll_region->paddr += ll_block->off;
> > ll_region->sz = ll_block->sz;
> >
> > @@ -416,7 +433,8 @@ static int dw_edma_pcie_probe(struct pci_dev
> *pdev,
> > return -ENOMEM;
> >
> > dt_region->vaddr.io += dt_block->off;
> > - dt_region->paddr = pci_bus_address(pdev, dt_block->bar);
> > + dt_region->paddr = dw_edma_get_phys_addr(pdev, vsec_data,
> > + dt_block->bar);
> > dt_region->paddr += dt_block->off;
> > dt_region->sz = dt_block->sz;
> > }
> > diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > index e3f8db4..47ecc84 100644
> > --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > @@ -225,7 +225,7 @@ static void dw_hdma_v0_sync_ll_data(struct
> dw_edma_chunk *chunk)
> > readl(chunk->ll_region.vaddr.io); }
> >
> > -static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool
> > first)
> > +static void dw_hdma_v0_core_ll_start(struct dw_edma_chunk *chunk,
> > +bool first)
> > {
> > struct dw_edma_chan *chan = chunk->chan;
> > struct dw_edma *dw = chan->dw;
> > @@ -263,6 +263,66 @@ static void dw_hdma_v0_core_start(struct
> dw_edma_chunk *chunk, bool first)
> > SET_CH_32(dw, chan->dir, chan->id, doorbell,
> > HDMA_V0_DOORBELL_START); }
> >
> > +static void dw_hdma_v0_core_non_ll_start(struct dw_edma_chunk
> *chunk)
> > +{
> > + struct dw_edma_chan *chan = chunk->chan;
> > + struct dw_edma *dw = chan->dw;
> > + struct dw_edma_burst *child;
> > + u32 val;
> > +
> > + list_for_each_entry(child, &chunk->burst->list, list) {
> > + SET_CH_32(dw, chan->dir, chan->id, ch_en, BIT(0));
>
> Please name BIT(0) with a define.
>
Sure, defined a macro HDMA_V0_CH_EN for clarity.
> > +
> > + /* Source address */
> > + SET_CH_32(dw, chan->dir, chan->id, sar.lsb,
> > + lower_32_bits(child->sar));
> > + SET_CH_32(dw, chan->dir, chan->id, sar.msb,
> > + upper_32_bits(child->sar));
> > +
> > + /* Destination address */
> > + SET_CH_32(dw, chan->dir, chan->id, dar.lsb,
> > + lower_32_bits(child->dar));
> > + SET_CH_32(dw, chan->dir, chan->id, dar.msb,
> > + upper_32_bits(child->dar));
> > +
> > + /* Transfer size */
> > + SET_CH_32(dw, chan->dir, chan->id, transfer_size,
> > + child->sz);
> > +
> > + /* Interrupt setup */
> > + val = GET_CH_32(dw, chan->dir, chan->id, int_setup) |
> > + HDMA_V0_STOP_INT_MASK |
> > + HDMA_V0_ABORT_INT_MASK |
> > + HDMA_V0_LOCAL_STOP_INT_EN |
> > + HDMA_V0_LOCAL_ABORT_INT_EN;
> > +
> > + if (!(dw->chip->flags & DW_EDMA_CHIP_LOCAL)) {
> > + val |= HDMA_V0_REMOTE_STOP_INT_EN |
> > + HDMA_V0_REMOTE_ABORT_INT_EN;
> > + }
> > +
> > + SET_CH_32(dw, chan->dir, chan->id, int_setup, val);
> > +
> > + /* Channel control setup */
> > + val = GET_CH_32(dw, chan->dir, chan->id, control1);
> > + val &= ~HDMA_V0_LINKLIST_EN;
> > + SET_CH_32(dw, chan->dir, chan->id, control1, val);
> > +
> > + /* Ring the doorbell */
> > + SET_CH_32(dw, chan->dir, chan->id, doorbell,
> > + HDMA_V0_DOORBELL_START);
>
> Doesn't the code explain itself already, why you need to have that comment
> above it, it doesn't seem to add any real value?
>
I followed the existing comment pattern and applied the same here.
I will remove this comment as pointed out it is self-explanatory.
> > + }
> > +}
> > +
> > +static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool
> > +first) {
> > + struct dw_edma_chan *chan = chunk->chan;
> > +
> > + if (!chan->non_ll)
> > + dw_hdma_v0_core_ll_start(chunk, first);
> > + else
> > + dw_hdma_v0_core_non_ll_start(chunk);
> > +}
> > +
> > static void dw_hdma_v0_core_ch_config(struct dw_edma_chan *chan) {
> > struct dw_edma *dw = chan->dw;
> > diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h index
> > 3080747..78ce31b 100644
> > --- a/include/linux/dma/edma.h
> > +++ b/include/linux/dma/edma.h
> > @@ -99,6 +99,7 @@ struct dw_edma_chip {
> > enum dw_edma_map_format mf;
> >
> > struct dw_edma *dw;
> > + bool non_ll;
> > };
> >
> > /* Export to the platform drivers */
> >
>
> --
> i.
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