[PATCH v2 0/4] xen/arm: add i.MX8M platform and UART support

[Wig Cheng <onlywig@xxxxxxxxx>]

Following Michal Orzel's review of v1, this series adds Xen support for
the NXP i.MX8M family (i.MX8MP / MQ / MM / MN).  It provides the console
UART driver, its early printk, the platform glue (SiP SMC whitelist for
the calls the dom0 kernel issues to TF-A), and a MAINTAINERS entry.

Tested on i.MX8MP (4x Cortex-A53, GICv3) with the vendor kernel 6.18:
dom0 boots to login on the hypervisor console, and a domU starts with a
PV disk and virtio devices running a full Wayland distro.

Notes for reviewers:

- Unlike i.MX8MQ, the i.MX8MP device tree uses the GIC as the root
  interrupt controller (interrupt-parent = <&gic>), so no device-tree
  workaround is needed and power domains keep working.

- The i.MX8M family has no SMMU, so device passthrough relies on the
  1:1 direct-mapped hardware domain.

- The SiP SMC whitelist forwards only the specific subfunctions the
  dom0 kernel issues, extracted from the vendor kernel call sites.
  DDR DVFS is left at service level because its reg1 is a frequency
  setpoint rather than a fixed subfunction id.  No call was denied at
  runtime.

Changes since v1:

Patch 1 (UART driver):
- Documentation narrowed to the i.MX8M family (dropped i.MX6/7).
- Relicensed the new files as GPL-2.0-only.
- Dropped the stale file-path lines from the file headers.
- Renamed the header guard to ASM_IMX_UART_H.
- Removed unused register/bit macros; header is now asm-safe (BIT(n, U)).
- Also clear UCR1_TXMPTYEN on init; documented that the console is
  driven entirely through UCR1.

Patch 2 (early printk):
- bne -> b.ne.

Patch 3 (platform):
- Build the SiP function IDs with ARM_SMCCC_CALL_VAL (IMX_SIP_FID),
  matching the i.MX8QM platform.
- Whitelist per subfunction (GPC, SRC, NoC) instead of whole services;
  DDR DVFS and SoC info kept at service level with a comment on why.
- Dropped the BBSM call, which is not issued on i.MX8M.
- Fixed the misleading "secure RTC" comment and a stray space.

Patch 4 (new):
- MAINTAINERS entry, as a separate patch.

v1: https://lore.kernel.org/xen-devel/20260814162535.331459-1-onlywig@xxxxxxxxx/


Wig Cheng (4):
  xen/char: add classic i.MX UART driver
  xen/arm64: add early printk for the classic i.MX UART
  xen/arm: add i.MX8M platform support
  MAINTAINERS: add myself as reviewer of i.MX8M related patches

 MAINTAINERS                           |   7 +
 xen/arch/arm/Kconfig.debug            |  12 ++
 xen/arch/arm/arm64/debug-imx-uart.inc |  37 +++++
 xen/arch/arm/include/asm/imx-uart.h   |  57 +++++++
 xen/arch/arm/platforms/Makefile       |   1 +
 xen/arch/arm/platforms/imx8m.c        | 152 +++++++++++++++++
 xen/drivers/char/Kconfig              |   8 +
 xen/drivers/char/Makefile             |   1 +
 xen/drivers/char/imx-uart.c           | 226 ++++++++++++++++++++++++++
 9 files changed, 501 insertions(+)
 create mode 100644 xen/arch/arm/arm64/debug-imx-uart.inc
 create mode 100644 xen/arch/arm/include/asm/imx-uart.h
 create mode 100644 xen/arch/arm/platforms/imx8m.c
 create mode 100644 xen/drivers/char/imx-uart.c

-- 
2.43.0