spi: dw: Allow interface drivers to limit data I/O to word sizes
The commit dd114443 ("spi: dw-spi: Convert 16bit accesses to 32bit accesses") changed all 16bit accesses in the DW_apb_ssi driver to 32bit. This, unfortunately, breaks data register access on picoXcell, where the DW IP needs data register accesses to be word accesses (all other accesses appear to be OK). This change introduces a new master variable to allow interface drivers to specify that 16bit data transfer I/O is required. This change also introduces the ability to set this variable via device tree bindings in the MMIO interface driver. Both the core and the MMIO interface driver default to the current 32bit behaviour. Before this change, on a picoXcell pc3x3: spi_master spi32766: interrupt_transfer: fifo overrun/underrun m25p80 spi32766.0: error -5 reading 9f m25p80: probe of spi32766.0 failed with error -5 After this change: m25p80 spi32766.0: m25p40 (512 Kbytes) Fixes: dd114443 ("spi: dw-spi: Convert 16bit accesses to 32bit accesses") Signed-off-by: NMichael van der Westhuizen <michael@smart-africa.com> Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: NMark Brown <broonie@kernel.org>
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