[RESEND,v2] spi: dw: Add deferred DMA-channels setup support

Currently if the source DMA device isn't ready to provide the channels
capable of the SPI DMA transfers, the DW SSI controller will be registered
with no DMA support. It isn't right since all what the driver needs to do
is to postpone the probe procedure until the DMA device is ready. Let's
fix that in the framework of the DWC SSI generic DMA implementation. First
we need to use the dma_request_chan() method instead of the
dma_request_slave_channel() function, because the later one is deprecated
and most importantly doesn't return the failure cause but the
NULL-pointer. Second we need to stop the DW SSI controller probe procedure
if the -EPROBE_DEFER error is returned on the DMA initialization. The
procedure will resume later when the channels are ready to be requested.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

---

Link: https://lore.kernel.org/linux-spi/20220610075006.10025-1-Sergey.Semin@baikalelectronics.ru/
Changelog v2:
- Just resend.
- Rebase onto the kernel v5.19-rcX.
---
 drivers/spi/spi-dw-core.c |  5 ++++-
 drivers/spi/spi-dw-dma.c  | 25 ++++++++++++++++++-------
 2 files changed, 22 insertions(+), 8 deletions(-)

On Sat, 25 Jun 2022 00:06:23 +0300, Serge Semin wrote:
> Currently if the source DMA device isn't ready to provide the channels
> capable of the SPI DMA transfers, the DW SSI controller will be registered
> with no DMA support. It isn't right since all what the driver needs to do
> is to postpone the probe procedure until the DMA device is ready. Let's
> fix that in the framework of the DWC SSI generic DMA implementation. First
> we need to use the dma_request_chan() method instead of the
> dma_request_slave_channel() function, because the later one is deprecated
> and most importantly doesn't return the failure cause but the
> NULL-pointer. Second we need to stop the DW SSI controller probe procedure
> if the -EPROBE_DEFER error is returned on the DMA initialization. The
> procedure will resume later when the channels are ready to be requested.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: dw: Add deferred DMA-channels setup support
      commit: e95a1cd2cfe722dc8434db6de33958035853aa05

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

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Thanks,
Mark