[v7,6/6] mmc: sh_mobile_sdhi: Add tuning support

Add tuning support for use with SDR104 mode
This includes adding support for the sampling clock controller (SCC).

Based on work by Ai Kyuse.

Cc: Ai Kyuse <ai.kyuse.uw@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
---
v6 [Simon Horman]
* Rebase to use host->taps

v5 [Simon Horman]
* As suggested by Ulf Hansson
  - Use more descriptive name for callback to check for SSC error
* Correct return statement in sh_mobile_sdhi_hw_reset
* Reinstate Gen3 tuning support

v4 [Simon Horman]
As suggested by Geert Uytterhoeven:
* guard SDR104 specific portion of probe with host->mmc->caps &
  MMC_CAP_UHS_SDR104
* As suggested by Wolfram Sang:
  - Pass priv to sd_scc_{read,write}32 to save host_to_priv access
    for each call
  - Use 0x0 instead of other representations of 0 in hex
  - Use CLK_CTL_SCLKEN
  - Do not add unused SH_MOBILE_SDHI_MAX_TAP
  - Use ternary operator in sh_mobile_sdhi_select_tuning
  - Do include as yet unsupported HS200 in error string
* Reintroduce retuning support: This was removed in v3.
* Revert to algorithm in v1 patchset, on further reading of the documentation
  it appears to be correct.

v3 [Simon Horman]
* As suggested by Kuninori Morimoto:
  - Do not add unused retuning callback to struct tmio_mmc_host
  - Change return type of prepare_tuning callback to void
  - Add tap_size parameter to select_tuning callback

v2 [Simon Horman]
* As suggested by Kuninori Morimoto
  - Use host->mmc->caps & MMC_CAP_UHS_SDR104 instead of
    pdata->flags & TMIO_MMC_HAS_UHS_SCC to avoid needing the
    MMC_CAP_UHS_SDR104 flag at all.
    N.B: Morimoto-san suggested using but this flag is not actually
    set there in by current probe come.
  - Simplify logic in sh_mobile_sdhi_inquiry_tuning
* As suggested by Wolfram Sang
  - Use clk_rate instead of clk for field in struct sh_mobile_sdhi_scc
  - Remove inquiry_tuning callback which is now unnecessary as calling
    of tuning is handled by the core
  - Removed unused sh_mobile_sdhi_set_clk_div callback
  - Save sci_base address rather than calculating it on each read and write
* Update selection logic in sh_mobile_sdhi_select_tuning to match spec
* Use bool instead of long for taps parameter of
  sh_mobile_sdhi_select_tuning()
* Return 0 from sh_mobile_sdhi_init_tuning() if the
  SDR104 capability is not set and thus tuning should not
  be performed because it is not supported by the hardware

v1 [Simon Horman]
* Rebase
* Always use value of 0x8 for TAPNUM field of DTCNTL register
  rather than reading value from DT property. There does not
  seem to be a need to expose this in DT at this point.
* Do not include tmio_mmc_start_signal_voltage_switch changes which
  are already in mainline in a different form
* Do not add renesas,clk-rate property as the max-frequency property, which
  is now present in mainline, seems to provide the needed rate
* Omit Gen3 specific changes
* Do not provide renesas,mmc-scc-tappos DT property.
  Instead, always use taps provided in driver.
* Do not parse sd-uhs-sdr50 and sd-uhs-sdr104 properties.
  This is handled by the core.

v0 [Ai Kyuse]

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
---
 drivers/mmc/host/sh_mobile_sdhi.c | 265 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 264 insertions(+), 1 deletion(-)

[v7,6/6] mmc: sh_mobile_sdhi: Add tuning support

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