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Douglas Anderson b9364eed92 drm/msm/dpu: Move min BW request and full BW disable back to mdss In commit `a670ff578f` ("drm/msm/dpu: always use mdp device to scale bandwidth") we fully moved interconnect stuff to the DPU driver. This had no change for sc7180 but _did_ have an impact for other SoCs. It made them match the sc7180 scheme. Unfortunately, the sc7180 scheme seems like it was a bit broken. Specifically the interconnect needs to be on for more than just the DPU driver's AXI bus. In the very least it also needs to be on for the DSI driver's AXI bus. This can be seen fairly easily by doing this on a ChromeOS sc7180-trogdor class device: set_power_policy --ac_screen_dim_delay=5 --ac_screen_off_delay=10 sleep 10 cd /sys/bus/platform/devices/ae94000.dsi/power echo on > control When you do that, you'll get a warning splat in the logs about "gcc_disp_hf_axi_clk status stuck at 'off'". One could argue that perhaps what I have done above is "illegal" and that it can't happen naturally in the system because in normal system usage the DPU is pretty much always on when DSI is on. That being said: * In official ChromeOS builds (admittedly a 5.4 kernel with backports) we have seen that splat at bootup. * Even though we don't use "autosuspend" for these components, we don't use the "put_sync" variants. Thus plausibly the DSI could stay "runtime enabled" past when the DPU is enabled. Techncially we shouldn't do that if the DPU's suspend ends up yanking our clock. Let's change things such that the "bare minimum" request for the interconnect happens in the mdss driver again. That means that all of the children can assume that the interconnect is on at the minimum bandwidth. We'll then let the DPU request the higher amount that it wants. It should be noted that this isn't as hacky of a solution as it might initially appear. Specifically: * Since MDSS and DPU individually get their own references to the interconnect then the framework will actually handle aggregating them. The two drivers are _not_ clobbering each other. * When the Qualcomm interconnect driver aggregates it takes the max of all the peaks. Thus having MDSS request a peak, as we're doing here, won't actually change the total interconnect bandwidth (it won't be added to the request for the DPU). This perhaps explains why the "average" requested in MDSS was historically 0 since that one _would_ be added in. NOTE also that in the downstream ChromeOS 5.4 and 5.15 kernels, we're also seeing some RPMH hangs that are addressed by this fix. These hangs are showing up in the field and on _some_ devices with enough stress testing of suspend/resume. Specifically right at suspend time with a stack crawl that looks like this (from chromeos-5.15 tree): rpmh_write_batch+0x19c/0x240 qcom_icc_bcm_voter_commit+0x210/0x420 qcom_icc_set+0x28/0x38 apply_constraints+0x70/0xa4 icc_set_bw+0x150/0x24c dpu_runtime_resume+0x50/0x1c4 pm_generic_runtime_resume+0x30/0x44 __genpd_runtime_resume+0x68/0x7c genpd_runtime_resume+0x12c/0x20c __rpm_callback+0x98/0x138 rpm_callback+0x30/0x88 rpm_resume+0x370/0x4a0 __pm_runtime_resume+0x80/0xb0 dpu_kms_enable_commit+0x24/0x30 msm_atomic_commit_tail+0x12c/0x630 commit_tail+0xac/0x150 drm_atomic_helper_commit+0x114/0x11c drm_atomic_commit+0x68/0x78 drm_atomic_helper_disable_all+0x158/0x1c8 drm_atomic_helper_suspend+0xc0/0x1c0 drm_mode_config_helper_suspend+0x2c/0x60 msm_pm_prepare+0x2c/0x40 pm_generic_prepare+0x30/0x44 genpd_prepare+0x80/0xd0 device_prepare+0x78/0x17c dpm_prepare+0xb0/0x384 dpm_suspend_start+0x34/0xc0 We don't completely understand all the mechanisms in play, but the hang seemed to come and go with random factors. It's not terribly surprising that the hang is gone after this patch since the line of code that was failing is no longer present in the kernel. Fixes: `a670ff578f` ("drm/msm/dpu: always use mdp device to scale bandwidth") Fixes: `c33b7c0389` ("drm/msm/dpu: add support for clk and bw scaling for display") Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com> Tested-by: Jessica Zhang <quic_jesszhan@quicinc.com> # RB3 (sdm845) and Reviewed-by: Stephen Boyd <swboyd@chromium.org> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> Patchwork: https://patchwork.freedesktop.org/patch/487884/ Link: https://lore.kernel.org/r/20220531160059.v2.1.Ie7f6d4bf8cce28131da31a43354727e417cae98d@changeid Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>		2022-06-01 16:16:19 -07:00
arch	Driver core changes for 5.18-rc2	2022-04-10 09:55:09 -10:00
block	for-5.18/block-2022-04-01	2022-04-01 16:20:00 -07:00
certs	Kbuild updates for v5.18	2022-03-31 11:59:03 -07:00
crypto	for-5.18/64bit-pi-2022-03-25	2022-03-26 12:01:35 -07:00
Documentation	dt-bindings: display: msm: Add optional resets	2022-05-02 02:07:08 +03:00
drivers	drm/msm/dpu: Move min BW request and full BW disable back to mdss	2022-06-01 16:16:19 -07:00
fs	Driver core changes for 5.18-rc2	2022-04-10 09:55:09 -10:00
include	drm: introduce drm_writeback_connector_init_with_encoder() API	2022-05-02 02:12:59 +03:00
init	Kbuild updates for v5.18	2022-03-31 11:59:03 -07:00
ipc	fs: allocate inode by using alloc_inode_sb()	2022-03-22 15:57:03 -07:00
kernel	- A couple of fixes to cgroup-related handling of perf events	2022-04-10 07:08:22 -10:00
lib	Driver core changes for 5.18-rc2	2022-04-10 09:55:09 -10:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	- Allow the compiler to optimize away unused percpu accesses and change	2022-04-10 06:56:46 -10:00
net	NFS client bugfixes for Linux 5.18	2022-04-08 07:39:17 -10:00
samples	dma-mapping updates for Linux 5.18	2022-03-29 08:50:14 -07:00
scripts	modpost: restore the warning message for missing symbol versions	2022-04-03 03:11:51 +09:00
security	hardening updates for v5.18-rc1-fix1	2022-03-31 11:43:01 -07:00
sound	sound fixes for 5.18-rc1	2022-04-01 10:32:46 -07:00
tools	- Fix the MSI message data struct definition	2022-04-10 07:12:27 -10:00
usr	Kbuild updates for v5.18	2022-03-31 11:59:03 -07:00
virt	KVM: Remove dirty handling from gfn_to_pfn_cache completely	2022-04-02 05:34:41 -04:00
.clang-format	genirq/msi: Make interrupt allocation less convoluted	2021-12-16 22:22:20 +01:00
.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	.gitignore: ignore only top-level modules.builtin	2021-05-02 00:43:35 +09:00
.mailmap	mailmap: update Vasily Averin's email address	2022-04-08 14:20:36 -10:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: replace a Microchip AT91 maintainer	2022-02-09 11:30:01 +01:00
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	MAINTAINERS: Add Dmitry as MSM DRM driver co-maintainer	2022-05-07 12:02:29 -07:00
Makefile	Linux 5.18-rc2	2022-04-10 14:21:36 -10:00
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.