Re: [PATCH 0/3] spi: cadence-xspi: add ACMD mode support

["Nuno Sá" <nuno.sa@analog.com>]

On Sat, Nov 07, 2026 at 03:31:27PM +0800, Jisheng Zhang wrote:
> On Thu, Oct 29, 2026 at 03:53:07PM +0000, Nuno Sá wrote:
> > The Cadence xSPI driver currently drives every operation through STIG
> > mode, where the CPU builds each command and drains the data. The
> > controller also has an auto command (ACMD) mode where it runs whole
> > sequences on its own and can move data with its internal DMA, which
> > pays off for bulk reads.
> > 
> > Whether ACMD and the internal DMA can be used depends on the SoC
> > integration (external SRAM, the DMA bus requester interface being
> > wired), which the controller registers do not expose. Hence two new
> > devicetree properties: cdns,has-acmd and cdns,has-internal-dma.
> > 
> > For now, ACMD is only used for reads of at least 2048 bytes with an
> > address phase, using the internal DMA, and only when both properties
> > are set. Smaller reads and all other operations stay on STIG.
> > 
> > NOR and NAND are handled the same way: NAND operations are still issued
> > one by one, not combined into a single ACMD sequence, so no NAND
> > geometry is needed. The real gain is on large reads which, for NAND,
> > means chips supporting buffer/sequential read mode.
> > 
> > Another attempt for ACMD was sent in [1] but that relies on knowing the
> > NAND geometry which brings much more complexity given that it needs a
> > proper interface implemented in the spi-nand core. So we agreed on
> > starting with this simpler approach and then build on top of it if we
> > agree it pays off (mostly on cpu load).
> 
> Hi Nuno,
> 
> Thanks for this series though I can't test it because my platforms
> disables the ACMD during integration.
> 
> I just sent out a series to reduce the cpu load and improve performance
> (possibly with powerful system memcpy dma engine), if your platforms
> have the suitable memcpy dma engine, can you please try it?

Sure, I'll give it a run and compare stats! I need to first tidy up my v2
and will test afterwards. Should happen this week!

- Nuno Sá

> 
> Hi Fei,
> 
> can you plz try it too if your platform has suitable memcpy dma engine too?
> 
> Thanks
> > 
> > Some stats:
> > 
> > ACMD
> > -----
> > 
> > SPI-NOR - is25wx01g (only reads > 2k are done in ACMD )
> > -------
> > 
> > flash_speed -c 5 -d /dev/mtd4
> > not NAND flash, assume page size is 512 bytes.
> > scanning for bad eraseblocks
> > scanned 5 eraseblocks, 0 are bad
> > testing eraseblock write speed
> > eraseblock write speed is 1054 KiB/s
> > testing eraseblock read speed
> > eraseblock read speed is 106666 KiB/s
> > testing page write speed
> > page write speed is 1035 KiB/s
> > testing page read speed
> > page read speed is 15238 KiB/s
> > 
> > SPI-NAND - w25n08lw (all reads are ACMD given that page size is 4k)
> > --------
> > 
> > flash_speed -c 5 -d /dev/mtd5
> > scanning for bad eraseblocks
> > scanned 5 eraseblocks, 0 are bad
> > testing eraseblock write speed
> > eraseblock write speed is 6497 KiB/s
> > testing eraseblock read speed
> > eraseblock read speed is 44137 KiB/s
> > testing page write speed
> > page write speed is 6336 KiB/s
> > testing page read speed
> > page read speed is 16842 KiB/s
> > 
> > STIG
> > ----
> > 
> > SPI-NOR
> > -------
> > 
> > flash_speed -c 5 -d /dev/mtd4
> > not NAND flash, assume page size is 512 bytes.
> > scanning for bad eraseblocks
> > scanned 5 eraseblocks, 0 are bad
> > testing eraseblock write speed
> > eraseblock write speed is 1054 KiB/s
> > testing eraseblock read speed
> > eraseblock read speed is 64000 KiB/s
> > testing page write speed
> > page write speed is 1042 KiB/s
> > testing page read speed
> > page read speed is 14883 KiB/s
> > 
> > SPI-NAND (Cont mode)
> > --------
> > 
> > flash_speed -c 5 -d /dev/mtd5
> > scanning for bad eraseblocks
> > scanned 5 eraseblocks, 0 are bad
> > testing eraseblock write speed
> > eraseblock write speed is 6564 KiB/s
> > testing eraseblock read speed
> > eraseblock read speed is 18823 KiB/s
> > testing page write speed
> > page write speed is 6400 KiB/s
> > testing page read speed
> > page read speed is 18028 KiB/s
> > 
> > For now, we have a static threshold to decide to use ACMD or not. I do
> > understand that's not ideal. It might depend on sclk and number of lanes
> > so not sure if that value will be accurate for everybody. So, open to
> > suggestions if someone has something in mind regarding this.
> > 
> > [1]: https://lore.kernel.org/linux-spi/20260921093701.1341766-1-fei.xie@horizon.auto/
> > 
> > ---
> > Nuno Sá (3):
> >       spi: cadence-xspi: rename sdma_error to xfer_error
> >       spi: dt-bindings: cdns,xspi: add ACMD and internal DMA properties
> >       spi: cadence-xspi: add ACMD mode support
> > 
> >  .../devicetree/bindings/spi/cdns,xspi.yaml         |  18 ++
> >  drivers/spi/spi-cadence-xspi.c                     | 269 +++++++++++++++++++--
> >  2 files changed, 273 insertions(+), 14 deletions(-)
> > ---
> > base-commit: 7da2aca123754c0e06092bbe179d58078b58d8d4
> > change-id: 20261027-xspi-cadence-add-acmd-3c0e342cb4f4
> > --
> > 
> > Thanks!
> > - Nuno Sá
> >