On Thu, Jan 7, 2021 at 11:59 PM Steven Price steven.price@arm.com wrote:
On 05/01/2021 00:11, Nicolas Boichat wrote:
GPUs with more than a single regulator (e.g. G-57 on MT8183) will require platform-specific handling, disable devfreq for now.
Can you explain what actually goes wrong here? AFAICT the existing code does support controlling multiple regulators - but clearly this is the first platform that exercises that code with num_supplies>1.
Sure, I should have expanded in the commit message, will do in v9.
We have support for >1 supplies, and we need to enable them to get the GPU running _at all_ (and the default voltages should be safe by design).
For devfreq though: 1. There are constraints on the voltage difference between the core and SRAM, we have this caterpillar logic downstream [1], so somebody will need to port it (TBH I don't think it's overly critical at this point, as Bifrost support is still not very mature from what I can see, and devfreq is purely a performance thing). 2. The core [2] does not support multiple regulators, so we'll need custom code anyway. Even if we didn't have constraints.
[1] https://chromium.googlesource.com/chromiumos/third_party/kernel/+/refs/heads... [2] https://elixir.bootlin.com/linux/latest/source/drivers/opp/core.c#L679
Steve
Signed-off-by: Nicolas Boichat drinkcat@chromium.org
Changes in v6:
- New change
drivers/gpu/drm/panfrost/panfrost_devfreq.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c index f44d28fad085..1f49043aae73 100644 --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c @@ -92,6 +92,15 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev) struct thermal_cooling_device *cooling; struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
if (pfdev->comp->num_supplies > 1) {/** GPUs with more than 1 supply require platform-specific handling:* continue without devfreq*/DRM_DEV_ERROR(dev, "More than 1 supply is not supported yet\n");return 0;}opp_table = dev_pm_opp_set_regulators(dev, pfdev->comp->supply_names, pfdev->comp->num_supplies); if (IS_ERR(opp_table)) {