BCM63xx HSSPI controller has the same issue as BCM63xx SPI controller: it doesn't allow keeping CS active between transfers. However, this controller allows changing CS polarities, which is used in the linux upstream driver to manage CS as desired.
Álvaro Fernández Rojas (4): dm: spi: add BCM63xx HSSPI driver mips: bmips: add bcm63xx-hsspi driver support for BCM6328 mips: bmips: add bcm63xx-hsspi driver support for BCM63268 mips: bmips: enable the SPI flash on the Comtrend AR-5387un
arch/mips/dts/brcm,bcm63268.dtsi | 21 ++ arch/mips/dts/brcm,bcm6328.dtsi | 24 ++ arch/mips/dts/comtrend,ar-5387un.dts | 12 + configs/comtrend_ar5387un_ram_defconfig | 8 + drivers/spi/Kconfig | 8 + drivers/spi/Makefile | 1 + drivers/spi/bcm63xx_hsspi.c | 392 ++++++++++++++++++++++++++++++++ 7 files changed, 466 insertions(+) create mode 100644 drivers/spi/bcm63xx_hsspi.c