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Similar to sc7180 (see the patch ("arm64: dts: qcom: sc7180: Fix
trogdor qspi pin config")), we should adjust the qspi pin config for
sc7280.
I won't re-describe all the research/arguments in the sc7180 patch
here, but there are a few differences for sc7280 worth noting:
1. On herobrine the SPI flash (qspi) is wired up differently on the
board. Rather than Cr50 and the AP being wired directly together,
there's actually a mux that will _either_ connect the AP to the
flash or Cr50 to the flash. This means that the internal pulls on
Cr50 don't affect us and we should enable our own pulldowns.
2. On herobrine, EEs added an external pulldown on the MISO line. The
argument in the schematic said that we added it (but not one on
MOSI and CLK) because Cr50 already enabled pulldowns on MOSI and
CLK. ...though, as per #1, those Cr50 pulldowns would only affect
the line when the mux was swung to Cr50.
The ironic result of #1 and #2 is that the external pulldowns on
CLK/MISO/MOSI on herobrine are _exactly opposite_ of the ones on
trogdor.
3. While I still don't have the actual exact schematics for all
variants of IDP/CRD that were produced, I have some reference
schematics that give me a belief of how the qspi is hooked up
there. From this, I'm fairly certain that all of the older variants
of IDP/CRD either have a pulldown on the CLK/MOSI/MISO lines (maybe
through a direct connect to Cr50) or have no pull (in other words,
they don't have a pullup). I'll go ahead and enable internal
pulldowns on all the lines since that won't hurt to double-pull if
there's an external pulldown and it's nice to have a pulldown if
there's nothing external. Note that this only affects _older_
CRDs. Newer revs are considered "herobrine" (see the hoglin/zoglin
device trees).
4. I didn't find the same strange "auto-switch-to-keeper" at suspend
when probing on sc7280. Whatever pulls (or lack thereof) I left at
suspend time seemed to persist into suspend.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230323102605.13.Ib44c3e417c414a4227db8def75ded37ad368212c@changeid
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