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AMD-Xilinx GQSPI controller has two advanced mode that allows the controller to consider two flashes as one single device. One of these two mode is the parallel mode in which each byte of data is stored in both devices, the even bits in the lower flash & the odd bits in the upper flash. The byte split is automatically handled by the QSPI controller. The other mode is the stacked mode in which both the flashes share the same SPI bus but each of the device contain half of the data. In this mode, the controller does not follow CS requests but instead internally wires the two CS levels with the value of the most significant address bit. For supporting both these modes SPI core need to be updated for providing multiple CS for a single SPI device. For adding multi CS support the SPI device need to be aware of all the CS values. So, the "chip_select" member in the spi_device structure is now an array that holds all the CS values. spi_device structure now has a "cs_index_mask" member. This acts as an index to the chip_select array. If nth bit of spi->cs_index_mask is set then the driver would assert spi->chip_select[n]. In parallel mode all the chip selects are asserted/de-asserted simultaneously and each byte of data is stored in both devices, the even bits in one, the odd bits in the other. The split is automatically handled by the GQSPI controller. The GQSPI controller supports a maximum of two flashes connected in parallel mode. A SPI_CONTROLLER_MULTI_CS flag bit is added in the spi controller flags, through ctlr->flags the spi core will make sure that the controller is capable of handling multiple chip selects at once. For supporting multiple CS via GPIO the cs_gpiod member of the spi_device structure is now an array that holds the gpio descriptor for each chipselect. CS GPIO is not tested on our hardware, but it has been tested by @Stefan https://lore.kernel.org/all/005001da1efc$619ad5a0$24d080e0$@opensource.cirrus.com/ Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com> Tested-by: Stefan Binding <sbinding@opensource.cirrus.com> Link: https://lore.kernel.org/r/20231125092137.2948-4-amit.kumar-mahapatra@amd.com Signed-off-by: Mark Brown <broonie@kernel.org> |
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