[PATCH 0/7] mmc: meson-gx: clean up and tuning update

[Jerome Brunet]

The purpose of this series is too improve reliability of the amlogic mmc
driver on new (g12a) and old ones (axg, gxl, gxbb, etc...)

* The 3 first patches are just harmless clean ups.
* Patch 4 makes sure HS400 can't be enabled, we still have not been able
  to crack this modes.
* Patch 5 removes some clock glitches when switching to DDR modes
* Patch 6 and 7 changes the tuning method from Rx phase to signal
  resampling. It could have been done in a single patch but the unified
  diff was extremely ugly. The change has been split in two patches to
  ease review.

The last tuning update that went through was meant to improve the axg
support. Since then, it was reported to break some other boards, like the
s912 vim2.

Also with the current tuning method, it was impossible to find phase
settings which would work on all the SoC, including the new ones.

After redoing all the tests from scratch, it appeared that Rx phase made
(strangely) almost no difference, especially on g12a and axg.
It is important to have a phase shift between the Core and Tx clock, 180
works best.

I discussed the test results with Amlogic. They suggested to use 180/0 or
0/180 for the Core and Tx phase. For tuning, they suggested to use
signal resampling.

So far, so good ... here the platform and modes tested:

NanoPi-K2 (S905): SD UHS SDR50/DDR50, SDIO HS
Odroid-C2 (S905): SD UHS SDR50/DDR50, eMMC DDR52/HS200
Khadas Vim (S905X): SD HS, SDIO HS, eMMC HS200
Libretech CC (S905X): SD HS, eMMC HS200
Khadas Vim2 (S912): SD HS, SDIO HS, eMMC HS200
S400 (A113D): SDIO UHS SDR104, eMMC DDR52/HS200
U200 (S905D2): SD HS, eMMC DDR52/HS200
SEI510 (S905X2): SD HS, eMMC DDR52/HS200

Jerome Brunet (7):
  mmc: meson-gx: remove open coded read with timeout
  mmc: meson-gx: ack only raised irq
  mmc: meson-gx: irq is not shared
  mmc: meson-gx: disable HS400
  mmc: meson-gx: avoid clock glitch when switching to DDR modes
  mmc: meson-gx: remove Rx phase tuning
  mmc: meson-gx: add signal resampling tuning

 drivers/mmc/host/meson-gx-mmc.c | 418 +++++++++-----------------------
 1 file changed, 113 insertions(+), 305 deletions(-)

-- 
2.20.1