[v2,0/2] spi: s3c64xx: add support exynos990-spi to new port config data

Message

Denzeel Oliva Feb. 13, 2025, 8:40 p.m. UTC

Exynos990 uses the same version of USI SPI (v2.1) as the GS101.
Removed fifo_lvl_mask and rx_lvl_offset, and changed to the new data
configuration port.

The difference from other new port configuration data is that fifo_depth
is only specified in fifo-depth in DT.

Exynos 990 data for SPI:
- The depth of the FIFO is not the same size on all nodes.
  A depth of 64 bytes is used on most nodes,
  while a depth of 256 bytes is used on 3 specific nodes (SPI 8/9/10).
- The Exynos 990 only allows access to 32-bit registers.
  If access is attempted with a different size, an error interrupt
  is generated. Therefore, it is necessary to perform write accesses to
  registers in 32-bit blocks.

Changes in v2:
- Added a default "fifo_depth = 64" to prevent crashes when "fifo-depth"
  is missing in the device tree (avoids divide-by-zero issues).
- No other functional changes.

Denzeel Oliva (2):
  spi: dt-bindings: samsung: add samsung,exynos990-spi compatible
  spi: s3c64xx: add support exynos990-spi to new port config data

 .../devicetree/bindings/spi/samsung,spi.yaml    |  1 +
 drivers/spi/spi-s3c64xx.c                       | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

Comments

Tudor Ambarus Feb. 14, 2025, 6:31 a.m. UTC | #1

On 2/13/25 8:40 PM, Denzeel Oliva wrote:
> - Added a default "fifo_depth = 64" to prevent crashes when "fifo-depth"
>   is missing in the device tree (avoids divide-by-zero issues).

no, you shouldn't use fifo_depth as a fallback, it's misleading.
fifo_depth shall be used only if all your SPI instances use the same
FIFO size. If that's not the case, as in yours, you specify the FIFO
depth via DT.

You need to determine whether your IP works with 0 sized FIFOs and if
not, make the the DT fifo-depth mandatory and check that its value is > 0.

If the IP works with 0 sized FIFOs, you need to update the driver to
allow that and let the fifo-depth property optional in DT.