On 09/01/2020 12:01 pm, Steven Price wrote:
On 08/01/2020 05:23, Nicolas Boichat wrote:
Hi!
Sorry for the long delay since
https://patchwork.kernel.org/patch/11132381/,
finally got around to give this a real try.
The main purpose of this series is to upstream the dts change and the
binding
document, but I wanted to see how far I could probe the GPU, to check
that the
binding is indeed correct. The rest of the patches are
RFC/work-in-progress, but
I think some of them could already be picked up.
So this is tested on MT8183 with a chromeos-4.19 kernel, and a ton of
backports to get the latest panfrost driver (I should probably try on
linux-next at some point but this was the path of least resistance).
I tested it as a module as it's more challenging (originally probing
would
work built-in, on boot, but not as a module, as I didn't have the power
domain changes, and all power domains are on by default during boot).
Probing logs looks like this, currently:
[ 221.867726] panfrost 13040000.gpu: clock rate = 511999970
[ 221.867929] panfrost 13040000.gpu: Linked as a consumer to
regulator.14
[ 221.868600] panfrost 13040000.gpu: Linked as a consumer to
regulator.31
[ 221.870586] panfrost 13040000.gpu: Linked as a consumer to
genpd:0:13040000.gpu
[ 221.871492] panfrost 13040000.gpu: Linked as a consumer to
genpd:1:13040000.gpu
[ 221.871866] panfrost 13040000.gpu: Linked as a consumer to
genpd:2:13040000.gpu
[ 221.872427] panfrost 13040000.gpu: mali-g72 id 0x6221 major 0x0
minor 0x3 status 0x0
[ 221.872439] panfrost 13040000.gpu: features: 00000000,13de77ff,
issues: 00000000,00000400
[ 221.872445] panfrost 13040000.gpu: Features: L2:0x07120206
Shader:0x00000000 Tiler:0x00000809 Mem:0x1 MMU:0x00002830 AS:0xff JS:0x7
[ 221.872449] panfrost 13040000.gpu: shader_present=0x7 l2_present=0x1
[ 221.873526] panfrost 13040000.gpu: error powering up gpu stack
[ 221.878088] [drm] Initialized panfrost 1.1.0 20180908 for
13040000.gpu on minor 2
[ 221.940817] panfrost 13040000.gpu: error powering up gpu stack
[ 222.018233] panfrost 13040000.gpu: error powering up gpu stack
(repeated)
It's interesting that it's only the stack that is failing. In hardware
there's a dependency: L2->stack->shader - so in theory the shader cores
shouldn't be able to power up either. There are some known hardware bugs
here though[1]:
MODULE_PARM_DESC(corestack_driver_control,
"Let the driver power on/off the GPU core stack
independently "
"without involving the Power Domain Controller. This should "
"only be enabled on platforms for which integration of the
PDC "
"to the Mali GPU is known to be problematic.");
[1]
https://github.com/ianmacd/d2s/blob/master/drivers/gpu/arm/b_r16p0/backend/gpu/mali_kbase_pm_driver.c#L57
It might be worth just dropping the code for powering up/down stacks and
let the GPU's own dependency management handle it.
FWIW I remember digging into that same message a while back (although
I've forgotten which particular GPU I was playing with at the time), and
concluded that the STACK_PWRON/STACK_READY registers might just not be
implemented on some GPUs, and/or this easy-to-overlook register bit
could be some kind of enable for the functionality:
https://github.com/ianmacd/d2s/blob/master/drivers/gpu/arm/b_r16p0/backend/gpu/mali_kbase_pm_driver.c#L1631
Since even in kbase this is all behind an 'expert' config option, I'm
inclined to agree that just dropping it from panfrost unless and until
it proves necessary is probably preferable to adding more logic and
inscrutable register-magic.
Robin.
Steve
So the GPU is probed, but there's an issue when powering up the STACK,
not
quite sure why, I'll try to have a deeper look, at some point.
Thanks!
Nicolas
v2:
- Use sram instead of mali_sram as SRAM supply name.
- Rename mali@ to gpu@.
- Add dt-bindings changes
- Stacking patches after the device tree change that allow basic
probing (still incomplete and broken).
Nicolas Boichat (7):
dt-bindings: gpu: mali-bifrost: Add Mediatek MT8183
arm64: dts: mt8183: Add node for the Mali GPU
drm/panfrost: Improve error reporting in panfrost_gpu_power_on
drm/panfrost: Add support for a second regulator for the GPU
drm/panfrost: Add support for multiple power domain support
RFC: drm/panfrost: Add bifrost compatible string
RFC: drm/panfrost: devfreq: Add support for 2 regulators
.../bindings/gpu/arm,mali-bifrost.yaml | 20 ++++
arch/arm64/boot/dts/mediatek/mt8183-evb.dts | 7 ++
arch/arm64/boot/dts/mediatek/mt8183.dtsi | 104 +++++++++++++++++
drivers/gpu/drm/panfrost/panfrost_devfreq.c | 18 +++
drivers/gpu/drm/panfrost/panfrost_device.c | 108 ++++++++++++++++--
drivers/gpu/drm/panfrost/panfrost_device.h | 7 ++
drivers/gpu/drm/panfrost/panfrost_drv.c | 1 +
drivers/gpu/drm/panfrost/panfrost_gpu.c | 15 ++-
8 files changed, 267 insertions(+), 13 deletions(-)
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