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Message-ID: <sshal25ch5pipzodbamg7h6k6scfzzsxnkox3dd5t6lvkrjis6@gmb55objtlgw>
Date: Wed, 10 Dec 2025 22:28:51 +0900
From: Manivannan Sadhasivam <mani@...nel.org>
To: "Verma, Devendra" <Devendra.Verma@....com>
Cc: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"vkoul@...nel.org" <vkoul@...nel.org>, "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Simek, Michal" <michal.simek@....com>
Subject: Re: [PATCH RESEND v6 2/2] dmaengine: dw-edma: Add non-LL mode
On Wed, Dec 10, 2025 at 11:39:59AM +0000, Verma, Devendra wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
>
> Hi Manivannan
>
> Please check my response inline.
>
> Regards,
> Devendra
>
> > -----Original Message-----
> > From: Manivannan Sadhasivam <mani@...nel.org>
> > Sent: Monday, December 8, 2025 11:00 AM
> > To: Verma, Devendra <Devendra.Verma@....com>
> > Cc: bhelgaas@...gle.com; vkoul@...nel.org; dmaengine@...r.kernel.org;
> > linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; Simek, Michal
> > <michal.simek@....com>
> > Subject: Re: [PATCH RESEND v6 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 Fri, Nov 21, 2025 at 05:04:55PM +0530, 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.
> > >
> >
> > Which in-kernel DMA client is using this non-LL mode?
> >
> > - Mani
> >
>
> Existing dma client application(s) can use the non-LL mode for the
> AMD (Xilinx) use case with the help of a simple peripheral_config
> variable which is part of the dma_slave_config structure.
There is no existing client driver making use of this non-LL mode. So
essentially, this patch is introducing the dead code.
> Though, no driver is using the non-LL mode as non-LL mode is not available
> in the current code.
Then introduce non-LL mode when such client drivers start using it.
- Mani
> Based on the following input (peripheral_config) from client in
> dw_edma_device_config(), non-LL mode can be decided by the controller driver.
> + if (config->peripheral_config)
> + non_ll = *(int *)config->peripheral_config;
>
> > > Signed-off-by: Devendra K Verma <devendra.verma@....com>
> > > ---
> > > Changes in v6
> > > Gave definition to bits used for channel configuration.
> > > Removed the comment related to doorbell.
> > >
> > > 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 | 61
> > > ++++++++++++++++++++++++++++++++++-
> > > drivers/dma/dw-edma/dw-hdma-v0-regs.h | 1 +
> > > include/linux/dma/edma.h | 1 +
> > > 6 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 3d7247c..e7e95df 100644
> > > --- a/drivers/dma/dw-edma/dw-edma-pcie.c
> > > +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
> > > @@ -269,6 +269,15 @@ 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) { @@
> > > -278,6 +287,7 @@ 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)
> > > @@ -302,21 +312,24 @@ 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 */
> > > @@ -364,6 +377,7 @@ 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; @@ -372,7 +386,7 @@
> > > 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];
> > > @@ -383,7 +397,8 @@ 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;
> > >
> > > @@ -392,12 +407,13 @@ 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];
> > > @@ -408,7 +424,8 @@ 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;
> > >
> > > @@ -417,7 +434,8 @@ 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..ee31c9a 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 +263,65 @@ 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,
> > > + HDMA_V0_CH_EN);
> > > +
> > > + /* 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);
> > > +
> > > + SET_CH_32(dw, chan->dir, chan->id, doorbell,
> > > + HDMA_V0_DOORBELL_START);
> > > + }
> > > +}
> > > +
> > > +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/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> > > b/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> > > index eab5fd7..7759ba9 100644
> > > --- a/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> > > +++ b/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> > > @@ -12,6 +12,7 @@
> > > #include <linux/dmaengine.h>
> > >
> > > #define HDMA_V0_MAX_NR_CH 8
> > > +#define HDMA_V0_CH_EN BIT(0)
> > > #define HDMA_V0_LOCAL_ABORT_INT_EN BIT(6)
> > > #define HDMA_V0_REMOTE_ABORT_INT_EN BIT(5)
> > > #define HDMA_V0_LOCAL_STOP_INT_EN BIT(4)
> > > 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 */
> > > --
> > > 1.8.3.1
> > >
> >
> > --
> > மணிவண்ணன் சதாசிவம்
--
மணிவண்ணன் சதாசிவம்
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