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Stephen Boyd 170b763597 drm/msm/dsi: Stash away calculated vco frequency on recalc 
A problem was reported on CoachZ devices where the display wouldn't come
up, or it would be distorted. It turns out that the PLL code here wasn't
getting called once dsi_pll_10nm_vco_recalc_rate() started returning the
same exact frequency, down to the Hz, that the bootloader was setting
instead of 0 when the clk was registered with the clk framework.

After commit 001d8dc338 ("drm/msm/dsi: remove temp data from global
pll structure") we use a hardcoded value for the parent clk frequency,
i.e.  VCO_REF_CLK_RATE, and we also hardcode the value for FRAC_BITS,
instead of getting it from the config structure. This combination of
changes to the recalc function allows us to properly calculate the
frequency of the PLL regardless of whether or not the PLL has been
clk_prepare()d or clk_set_rate()d. That's a good improvement.

Unfortunately, this means that now we won't call down into the PLL clk
driver when we call clk_set_rate() because the frequency calculated in
the framework matches the frequency that is set in hardware. If the rate
is the same as what we want it should be OK to not call the set_rate PLL
op. The real problem is that the prepare op in this driver uses a
private struct member to stash away the vco frequency so that it can
call the set_rate op directly during prepare. Once the set_rate op is
never called because recalc_rate told us the rate is the same, we don't
set this private struct member before the prepare op runs, so we try to
call the set_rate function directly with a frequency of 0. This
effectively kills the PLL and configures it for a rate that won't work.
Calling set_rate from prepare is really quite bad and will confuse any
downstream clks about what the rate actually is of their parent. Fixing
that will be a rather large change though so we leave that to later.

For now, let's stash away the rate we calculate during recalc so that
the prepare op knows what frequency to set, instead of 0. This way
things keep working and the display can enable the PLL properly. In the
future, we should remove that code from the prepare op so that it
doesn't even try to call the set rate function.

Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Abhinav Kumar <abhinavk@codeaurora.org>
Fixes: 001d8dc338 ("drm/msm/dsi: remove temp data from global pll structure")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20210608195519.125561-1-swboyd@chromium.org
Signed-off-by: Rob Clark <robdclark@chromium.org>
2021-06-10 07:57:48 -07:00
arch A set of irqchip updates: 2021-03-14 13:33:33 -07:00
block block: Discard page cache of zone reset target range 2021-03-11 11:49:25 -07:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto crypto: mips/poly1305 - enable for all MIPS processors 2021-03-08 11:52:17 +01:00
Documentation A set of irqchip updates: 2021-03-14 13:33:33 -07:00
drivers drm/msm/dsi: Stash away calculated vco frequency on recalc 2021-06-10 07:57:48 -07:00
fs Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
include clk: divider: add devm_clk_hw_register_divider 2021-04-07 11:05:44 -07:00
init Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel prctl: fix PR_SET_MM_AUXV kernel stack leak 2021-03-14 14:33:27 -07:00
lib kasan: fix KASAN_STACK dependency for HW_TAGS 2021-03-13 11:27:31 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
net NFS Client Bugfixes for Linux 5.10-rc3 2021-03-12 14:19:35 -08:00
samples Merge git://git.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2021-03-09 17:15:56 -08:00
scripts kbuild: fix ld-version.sh to not be affected by locale 2021-03-13 11:12:13 +09:00
security Revert 95ebabde38 ("capabilities: Don't allow writing ambiguous v3 file capabilities") 2021-03-12 15:27:14 -06:00
sound ALSA: hda/hdmi: Cancel pending works before suspend 2021-03-10 12:52:01 +01:00
tools A single objtool fix to handle the PUSHF/POPF validation correctly for the 2021-03-14 13:15:55 -07:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
Makefile Linux 5.12-rc3 2021-03-14 14:41:02 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.