[4.4,142/312] clk: rockchip: Revert "clk: rockchip: reset init state before mmc card initialization"

From: Douglas Anderson <dianders@chromium.org>

commit 4715f81afc342996f680b08c944a712d9cbef11b upstream.

This reverts commit 7a03fe6f48f3 ("clk: rockchip: reset init state
before mmc card initialization").

Though not totally obvious from the commit message nor from the source
code, that commit appears to be trying to reset the "_drv" MMC clocks to
90 degrees (note that the "_sample" MMC clocks have a shift of 0 so are
not touched).

The major problem here is that it doesn't properly reset things.  The
phase is a two bit field and the commit only touches one of the two
bits.  Thus the commit had the following affect:
- phase   0  => phase  90
- phase  90  => phase  90
- phase 180  => phase 270
- phase 270  => phase 270

Things get even weirder if you happen to have a bootloader that was
actually using delay elements (should be no reason to, but you never
know), since those are additional bits that weren't touched by the
original patch.

This is unlikely to be what we actually want.  Checking on rk3288-veyron
devices, I can see that the bootloader leaves these clocks as:
- emmc:  phase 180
- sdmmc: phase 90
- sdio0: phase 90

Thus on rk3288-veyron devices the commit we're reverting had the effect
of changing the eMMC clock to phase 270.  This probably explains the
scattered reports I've heard of eMMC devices not working on some veyron
devices when using the upstream kernel.

The original commit was presumably made because previously the kernel
didn't touch the "_drv" phase at all and relied on whatever value was
there when the kernel started.  If someone was using a bootloader that
touched the "_drv" phase then, indeed, we should have code in the kernel
to fix that.  ...and also, to get ideal timings, we should also have the
kernel change the phase depending on the speed mode.  In fact, that's
the subject of a recent patch I posted at
<https://patchwork.kernel.org/patch/9075141/>.

Ideally, we should take both the patch posted to dw_mmc and this
revert.  Since those will likely go through different trees, here I
describe behavior with the combos:

1. Just this revert: likely will fix rk3288-veyron eMMC on some devices
   + other cases; might break someone with a strange bootloader that
   sets the phase to 0 or one that uses delay elements (pretty
   unpredicable what would happen in that case).
2. Just dw_mmc patch: fixes everyone.  Effectly the dw_mmc patch will
   totally override the broken patch and fix everything.
3. Both patches: fixes everyone.  Once dw_mmc is initting properly then
   any defaults from the clock code doesn't mattery.

Fixes: 7a03fe6f48f3 ("clk: rockchip: reset init state before mmc card initialization")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[emmc and sdmmc still work on all current boards in mainline after this
revert, so they should take precedence over any out-of-tree board that
will hopefully again get fixed with the better upcoming dw_mmc change.]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

---
 drivers/clk/rockchip/clk-mmc-phase.c |   11 -----------
 1 file changed, 11 deletions(-)