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Unverified Commit c99182f7 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Mark Brown
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spi: sh-msiof: Document hardware limitations related to chip selects 



Guide users to maintain the proper balance between native and GPIO chip
selects.

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent b8761434

Documentation/devicetree/bindings/spi/sh-msiof.txt

+10 −0
Original line number Diff line number Diff line
@@ -41,6 +41,16 @@ Optional properties: 
			   0: MSIOF_SYNC

			   1: MSIOF_SS1

			   2: MSIOF_SS2

			 Hardware limitations related to chip selects:

			   - Native chip selects are always deasserted in

			     between transfers that are part of the same

			     message.  Use cs-gpios to work around this.

			   - All slaves using native chip selects must use the

			     same spi-cs-high configuration.  Use cs-gpios to

			     work around this.

			   - When using GPIO chip selects, at least one native

			     chip select must be left unused, as it will be

			     driven anyway.

- dmas                 : Must contain a list of two references to DMA

			 specifiers, one for transmission, and one for

			 reception.