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The UFS controller of the ExynosAuto v9 SoC supports a multi-host interface for I/O virtualization. In general, we're using para-virtualized driver to support a block device by several virtual machines. Multi-host functionality extends the host controller by providing register interfaces that can be used by each VM's UFS drivers respectively. This way we can provide direct access to the UFS device for multiple VMs similar to PCIe SR-IOV. We divide this M-HCI as PH (Physical Host) and VHs (Virtual Host). The PH supports all UFSHCI functions (all SAPs) like a conventional UFSHCI but the VH only supports data transfer functions. Thus, except UTP_CMD_SAP and UTP_TMPSAP, the PH should handle all the physical features. Provide an initial implementation of PH part. M-HCI can support up to four interfaces (1 for a PH and 3 for VHs) but this patch initially supports only 1 PH and 1 VH. For this, we uses TASK_TAG[7:5] field so TASK_TAG[4:0] for 32 doorbell will be supported. After the PH is initiated, this will send a ready message to VHs through a mailbox register. The message handler is not fully implemented yet such as supporting reset / abort cases. Link: https://lore.kernel.org/r/20211018124216.153072-14-chanho61.park@samsung.com Cc: Alim Akhtar <alim.akhtar@samsung.com> Cc: Kiwoong Kim <kwmad.kim@samsung.com> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> Reviewed-by: Inki Dae <inki.dae@samsung.com> Signed-off-by: Chanho Park <chanho61.park@samsung.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>