Re: [PATCH v4 4/8] dmaengine: dw-edma: rename wr(rd)_ch_cnt to ll_wr(rd)_cnt in struct dw_edma_chip

[Serge Semin <fancer.lancer@gmail.com>]

On Thu, Mar 10, 2022 at 10:51:51AM -0600, Zhi Li wrote:
> On Thu, Mar 10, 2022 at 10:26 AM Zhi Li <lznuaa@gmail.com> wrote:
> >
> > On Thu, Mar 10, 2022 at 6:37 AM Serge Semin <fancer.lancer@gmail.com> wrote:
> > >
> > > On Wed, Mar 09, 2022 at 03:12:00PM -0600, Frank Li wrote:
> > > > There are same name wr(rd)_ch_cnt in struct dw_edma. EDMA driver get
> > > > write(read) channel number from register, then save these into dw_edma.
> > > > Old wr(rd)_ch_cnt in dw_edma_chip actuall means how many link list memory
> > > > are avaiable in ll_region_wr(rd)[EDMA_MAX_WR_CH]. So rename it to
> > > > ll_wr(rd)_cnt to indicate actual usage.
> > >
> > > Hmm, I am not sure you are right here. AFAICS the
> > > drivers/dma/dw-edma/dw-edma-pcie.c driver either uses a statically
> > > defined number or Rd/Wr channels or just gets the number from the
> > > specific vsec PCIe capability. Then based on that the driver just
> > > redistributes the BARs memory amongst all the detected channels in
> > > accordance with the statically defined snps_edda_data structure.
> > > Basically the BARs memory serves as the Local/CPU/Application memory
> > > for the case if the controller is embedded into the PCIe Host/EP
> > > controller. See the patches which implicitly prove that:
> > > 31fb8c1ff962 ("dmaengine: dw-edma: Improve the linked list and data blocks definition")
> > > da6e0dd54135 ("dmaengine: dw-edma: Change linked list and data blocks offset and sizes")
> > >
> > > (That's why the logic of the DEV_TO_MEM/MEM_TO_DEV is inverted for the
> > > the drivers/dma/dw-edma/dw-edma-pcie.c platform.)
> > >
> > > So basically the wr_ch_cnt/rd_ch_cnt fields have been and is used as
> > > the number of actually available channels, not linked-list. While the
> > > notation suggested by you can be confusing, since the ll-memory allocated for
> > > each channel can be split up and initialized with numerous linked lists
> > > each of which is used one after another.
> > >
> > > I don't really see a well justified reason to additionally have the
> > > @wr_ch_cnt and @rd_ch_cnt fields in the dw_edma_chip seeing the number
> > > of channels can be auto-detected from the corresponding registers, except
> > > that to workaround a bogus hardware. So we can keep it, but please no
> > > renaming. It will only cause additional confusion.
> >

> > I agree that channel numbers can be obtained from the register.
> > but Caller don't know the channel number before calling dw_edma_probe.
> >
> > Caller may not init all ll_region_wr[EDMA_MAX_WR_CH],
> >
> > That's the reason I need a field to indicate how many ll_region_w
> > actually initialized.
> >
> > old wr_ch_cnt just plays the same role.
> 
> Anyway, it is not a big deal. I can skip this patch.

Ah, finally I see what you mean here. The patch seems reasonable now. No
objection against it then.

Reviewed-by: Serge Semin <fancer.lancer@gmail.com>

-Sergey

> 
> >
> > >
> > > -Sergey
> > >
> > > >
> > > > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > > > ---
> > > > new patch at v4
> > > >
> > > >  drivers/dma/dw-edma/dw-edma-core.c |  4 ++--
> > > >  drivers/dma/dw-edma/dw-edma-pcie.c | 12 ++++++------
> > > >  include/linux/dma/edma.h           |  8 ++++----
> > > >  3 files changed, 12 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > > > index 1abf41d49f75b..66dc650577919 100644
> > > > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > > > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > > > @@ -918,11 +918,11 @@ int dw_edma_probe(struct dw_edma_chip *chip)
> > > >       raw_spin_lock_init(&dw->lock);
> > > >
> > > >
> > > > -     dw->wr_ch_cnt = min_t(u16, chip->wr_ch_cnt,
> > > > +     dw->wr_ch_cnt = min_t(u16, chip->ll_wr_cnt,
> > > >                             dw_edma_v0_core_ch_count(dw, EDMA_DIR_WRITE));
> > > >       dw->wr_ch_cnt = min_t(u16, dw->wr_ch_cnt, EDMA_MAX_WR_CH);
> > > >
> > > > -     dw->rd_ch_cnt = min_t(u16, chip->rd_ch_cnt,
> > > > +     dw->rd_ch_cnt = min_t(u16, chip->ll_rd_cnt,
> > > >                             dw_edma_v0_core_ch_count(dw, EDMA_DIR_READ));
> > > >       dw->rd_ch_cnt = min_t(u16, dw->rd_ch_cnt, EDMA_MAX_RD_CH);
> > > >
> > > > diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c b/drivers/dma/dw-edma/dw-edma-pcie.c
> > > > index ae42bad24dd5a..7732537f96086 100644
> > > > --- a/drivers/dma/dw-edma/dw-edma-pcie.c
> > > > +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
> > > > @@ -230,14 +230,14 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > > >       chip->nr_irqs = nr_irqs;
> > > >       chip->ops = &dw_edma_pcie_core_ops;
> > > >
> > > > -     chip->wr_ch_cnt = vsec_data.wr_ch_cnt;
> > > > -     chip->rd_ch_cnt = vsec_data.rd_ch_cnt;
> > > > +     chip->ll_wr_cnt = vsec_data.wr_ch_cnt;
> > > > +     chip->ll_rd_cnt = vsec_data.rd_ch_cnt;
> > > >
> > > >       chip->reg_base = pcim_iomap_table(pdev)[vsec_data.rg.bar];
> > > >       if (!chip->reg_base)
> > > >               return -ENOMEM;
> > > >
> > > > -     for (i = 0; i < chip->wr_ch_cnt; i++) {
> > > > +     for (i = 0; i < chip->ll_wr_cnt; 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];
> > > > @@ -262,7 +262,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > > >               dt_region->sz = dt_block->sz;
> > > >       }
> > > >
> > > > -     for (i = 0; i < chip->rd_ch_cnt; i++) {
> > > > +     for (i = 0; i < chip->ll_rd_cnt; 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];
> > > > @@ -302,7 +302,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > > >               chip->reg_base);
> > > >
> > > >
> > > > -     for (i = 0; i < chip->wr_ch_cnt; i++) {
> > > > +     for (i = 0; i < chip->ll_wr_cnt; i++) {
> > > >               pci_dbg(pdev, "L. List:\tWRITE CH%.2u, BAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p, p=%pa)\n",
> > > >                       i, vsec_data.ll_wr[i].bar,
> > > >                       vsec_data.ll_wr[i].off, chip->ll_region_wr[i].sz,
> > > > @@ -314,7 +314,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
> > > >                       chip->dt_region_wr[i].vaddr, &chip->dt_region_wr[i].paddr);
> > > >       }
> > > >
> > > > -     for (i = 0; i < chip->rd_ch_cnt; i++) {
> > > > +     for (i = 0; i < chip->ll_rd_cnt; i++) {
> > > >               pci_dbg(pdev, "L. List:\tREAD CH%.2u, BAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p, p=%pa)\n",
> > > >                       i, vsec_data.ll_rd[i].bar,
> > > >                       vsec_data.ll_rd[i].off, chip->ll_region_rd[i].sz,
> > > > diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> > > > index e9ce652b88233..c2039246fc08c 100644
> > > > --- a/include/linux/dma/edma.h
> > > > +++ b/include/linux/dma/edma.h
> > > > @@ -40,8 +40,8 @@ enum dw_edma_map_format {
> > > >   * @nr_irqs:          total dma irq number
> > > >   * @ops                       DMA channel to IRQ number mapping
> > > >   * @reg_base          DMA register base address
> > > > - * @wr_ch_cnt                 DMA write channel number
> > > > - * @rd_ch_cnt                 DMA read channel number
> > > > + * @ll_wr_cnt                 DMA write link list number
> > > > + * @ll_rd_cnt                 DMA read link list number
> > > >   * @rg_region                 DMA register region
> > > >   * @ll_region_wr      DMA descriptor link list memory for write channel
> > > >   * @ll_region_rd      DMA descriptor link list memory for read channel
> > > > @@ -56,8 +56,8 @@ struct dw_edma_chip {
> > > >
> > > >       void __iomem            *reg_base;
> > > >
> > > > -     u16                     wr_ch_cnt;
> > > > -     u16                     rd_ch_cnt;
> > > > +     u16                     ll_wr_cnt;
> > > > +     u16                     ll_rd_cnt;
> > > >       /* link list address */
> > > >       struct dw_edma_region   ll_region_wr[EDMA_MAX_WR_CH];
> > > >       struct dw_edma_region   ll_region_rd[EDMA_MAX_RD_CH];
> > > > --
> > > > 2.24.0.rc1
> > > >