scsi: ufs: ufs-exynos: Multi-host configuration for ExynosAuto v9

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>