On Sat, Apr 25, 2020 at 12:51 AM Sylwester Nawrocki s.nawrocki@samsung.com wrote:
There might be hardware configurations where 64-bit data accesses to XHCI registers are not supported properly. This patch removes the readq/writeq so always two 32-bit accesses are used to read/write 64-bit XHCI registers, similarly as it is done in Linux kernel.
This patch fixes operation of the XHCI controller on RPI4 Broadcom BCM2711 SoC based board, where the VL805 USB XHCI controller is connected to the PCIe Root Complex, which is attached to the system through the SCB bridge.
Even though the architecture is 64-bit the PCIe BAR is 32-bit and likely the 64-bit wide register accesses initiated by the CPU are not properly translated to a sequence of 32-bit PCIe accesses. xhci_readq(), for example, always returns same value in upper and lower 32-bits, e.g. 0xabcd1234abcd1234 instead of 0x00000000abcd1234.
Cc: Sergey Temerkhanov s.temerkhanov@gmail.com Signed-off-by: Sylwester Nawrocki s.nawrocki@samsung.com
Changes since RFC:
- dropped Kconfig option, switched to not using readq/writeq unconditionally.
include/usb/xhci.h | 8 -------- 1 file changed, 8 deletions(-)
Reviewed-by: Bin Meng bmeng.cn@gmail.com