RISC-V: Add eMMC support for TH1520 boards

This series adds support for the eMMC on the BeagleV Ahead and the
Sipeed LicheePi 4A. This allows the kernel to boot with the rootfs on
eMMC.

I tested on top of v6.6-rc2 with this config [1]. I was able to boot
both the Ahead [2] and LPi4a [3] from eMMC. The following prerequisites
are required:

  [PATCH v2] riscv: dts: thead: set dma-noncoherent to soc bus [4]

I pushed a branch [5] with this patch series and the above patch for
those that find a git branch easier to test.

Please note that only the MMC controller connected to the eMMC device
is enabled in the device trees for these two boards. I did not yet
attempt to configure and use the microSD card slot. My preference is to
address that in a future patch series.

References:
[1] https://gist.github.com/pdp7/5fbdcf2a65eb1abdd3a29d519c19...
[2] https://gist.github.com/pdp7/91a801a5f8d1070c53509eda9800...
[3] https://gist.github.com/pdp7/1445c3c991e88fd69c60165cef65...
[4] https://lore.kernel.org/linux-riscv/20230912072232.2455-1...
[5] https://github.com/pdp7/linux/tree/b4/th1520-mmc

Changes since RFC v2:
- ADMA mode now works correctly due to a patch from Jisheng on the list
  ("riscv: dts: thead: set dma-noncoherent to soc bus") and this commit
  from Icenowy that is now merged: 8eb8fe67e2c8 ("riscv: errata: fix
  T-Head dcache.cva encoding").
- Expose __sdhci_execute_tuning from sdhci.c so that it can be called
  from th1520_execute_tuning()
- Refactor the define macros for all the PHY related registers to make
  it easier to understand the bit fields that the code is manipulating
- Replace magic numbers in the PHY register writes with proper defines 
- Replace non_removable in dwcmshc_priv with check of mmc_host.caps
- Drop dt prop "thead,io-fixed-1v8" and instead check for existing
  properties: "mmc-ddr-1_8v", "mmc-hs200-1_8v", or "mmc-hs400-1_8v"
- Rename dt prop from "thead,pull-up" to "thead,phy-pull-up" and
  improve the description in the dt binding
- Replace pull_up_en in dwcmshc_priv with bit field in new flags field
- Create th1520_set_uhs_signaling() and call dwcmshc_set_uhs_signaling()
  from it instead of adding th1520 code to dwcmshc_set_uhs_signaling()
- Return -EIO instead of -1 upon errors in th1520_execute_tuning()

Changes in RFC v2:
https://lore.kernel.org/linux-riscv/20230724-th1520-emmc-...
- Expand dwcmshc_priv based on driver in the T-Head 5.10 kernel:
  delay_line, non_removable, pull_up_en, io_fixed_1v8
- New boolean property "thead,pull-up" indicates phy pull-up config
- New boolean property "thead,io-fixed-1v8" indicates that io voltage
  should be set to 1.8V during reset
- Add th1520_phy_1_8v_init() as voltage_switch op
- Add th1520_execute_tuning() as the platform_execute_tuning op
- Added th1520_sdhci_reset() as the .reset op. This function will set
  io voltage to 1.8V after calling the standard sdhci_reset() function.
- Modified dwcmshc_set_uhs_signaling() to enable SDHCI_CTRL_VDD_180 when
  io_fixed_1v8 is true
- Add many defines for register offsets and settings based on the mmc
  support in the T-Head downstream v5.10 kernel

RFC v1 series:
https://lore.kernel.org/r/20230724-th1520-emmc-v1-0-cca1b...

Signed-off-by: Drew Fustini <dfustini@baylibre.com>
---
Drew Fustini (6):
      dt-bindings: mmc: sdhci-of-dwcmhsc: Add T-Head TH1520 support
      mmc: sdhci: add __sdhci_execute_tuning() to header
      mmc: sdhci-of-dwcmshc: Add support for T-Head TH1520
      riscv: dts: thead: Add TH1520 mmc controller and sdhci clock
      riscv: dts: thead: Enable BeagleV Ahead eMMC controller
      riscv: dts: thead: Enable LicheePi 4A eMMC controller

 .../bindings/mmc/snps,dwcmshc-sdhci.yaml           |   4 +
 arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dts |  15 +
 .../boot/dts/thead/th1520-lichee-module-4a.dtsi    |  15 +
 arch/riscv/boot/dts/thead/th1520.dtsi              |  15 +
 drivers/mmc/host/sdhci-of-dwcmshc.c                | 456 +++++++++++++++++++++
 drivers/mmc/host/sdhci.c                           |   2 +-
 drivers/mmc/host/sdhci.h                           |   1 +
 7 files changed, 507 insertions(+), 1 deletion(-)
---
base-commit: 3d01adbee80b2237c43e2e06d59e05aa243a0fe6
change-id: 20230921-th1520-mmc-518806aa55a8

Best regards,
-- 
Drew Fustini <dfustini@baylibre.com>