This compatible adds the ability for dw spi controller driver to work with the dw spi controller found on Alpine chips. The dw spi controller has an auto-deselect of Chip-Select, in case there is no data inside the Tx FIFO. While working on platforms with Alpine chips, auto-deselect mode causes an issue for some spi devices that can't handle the Chip-Select deselect in the middle of a transaction. It is a normal behavior for a Tx FIFO to be empty in the middle of a transaction, due to busy cpu. In the Alpine chip family an option to change the default behavior was added to the original dw spi controller to prevent this issue of de-asserting Chip-Select once TX FIFO is empty. The change was to allow SW manual control of the Chip-Select. With this change, as long as the Slave Enable Register is asserted, the Chip-Select will be asserted. As a result, it is necessary to deselect the Slave Select Register once the transaction is done. This feature is enabled via a new device compatible string called 'al,alpine-dw-apb-ssi'. Once the driver identifies the new compatible string, it enables the hw fixup logic, by writing to a dedicated register found in the IP reserved area and will start manual deselecting the Slave Select Register when the transfer ends. Signed-off-by: Talel Shenhar <talel@xxxxxxxxxx> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> --- Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt index 642d3fb..d25b1f8 100644 --- a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt +++ b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt @@ -2,7 +2,7 @@ Synopsys DesignWare AMBA 2.0 Synchronous Serial Interface. Required properties: - compatible : "snps,dw-apb-ssi" or "mscc,<soc>-spi", where soc is "ocelot" or - "jaguar2" + "jaguar2", or "al,alpine-dw-apb-ssi" - reg : The register base for the controller. For "mscc,<soc>-spi", a second register set is required (named ICPU_CFG:SPI_MST) - interrupts : One interrupt, used by the controller. -- 2.7.4
