On Fri, 27 Jan 2023 at 01:12, Saravana Kannan <saravanak@xxxxxxxxxx> wrote: > > On Thu, Jan 26, 2023 at 2:51 PM Dmitry Baryshkov > <dmitry.baryshkov@xxxxxxxxxx> wrote: > > > > On 25/01/2023 21:09, Rob Herring wrote: > > > On Tue, Jan 24, 2023 at 06:12:15PM -0800, Saravana Kannan wrote: > > >> On Wed, Jan 18, 2023 at 5:35 AM Rob Herring <robh+dt@xxxxxxxxxx> wrote: > > >>> > > >>> On Wed, Jan 18, 2023 at 3:11 AM Dmitry Baryshkov > > >>> <dmitry.baryshkov@xxxxxxxxxx> wrote: > > >>>> > > >>>> Do not create device link for clock controllers. Some of the clocks > > >>>> provided to the device via OF can be the clocks that are just parents to > > >>>> the clocks provided by this clock controller. Clock subsystem already > > >>>> has support for handling missing clock parents correctly (clock > > >>>> orphans). Later when the parent clock is registered, clocks get > > >>>> populated properly. > > >>>> > > >>>> An example of the system where this matters is the SDM8450 MTP board > > >>>> (see arch/arm64/boot/dts/qcom/sdm845-mtp.dts). Here the dispcc uses > > >>>> clocks provided by dsi0_phy and dsi1_phy device tree nodes. However the > > >>>> dispcc itself provides clocks to both PHYs, to the PHY parent device, > > >>>> etc. With just dsi0_phy in place devlink is able to break the > > >>>> dependency, but with two PHYs, dispcc doesn't get probed at all, thus > > >>>> breaking display support. > > >>>> > > >>>> Cc: Bjorn Andersson <andersson@xxxxxxxxxx> > > >>>> Cc: Stephen Boyd <sboyd@xxxxxxxxxx> > > >>>> Cc: Saravana Kannan <saravanak@xxxxxxxxxx> > > >>>> Cc: Abel Vesa <abel.vesa@xxxxxxxxxx> > > >>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > > >>>> --- > > >>>> > > >>>> This patch has been posted a year ago in January 2022 ([1]). Since that time > > >>>> Saravana failed to produce patches to assist in debugging the issue > > >>>> ([2]) or to fix the issue ([3]). The issue we observe has been described > > >>>> by Abel at ([4]). As we work on adding support for Dual DSI > > >>>> configurations, the issue becomes more and more important, since binding > > >>>> the whole display subsystem fails. > > >> > > >> I did send out a patch series[1] to try and fix this. Heck I even > > >> talked about this in LPC 2022. So I don't think it's accurate to say I > > >> didn't help debug this or fix this. There's some email thread in lore > > >> where Abel gave more details and I figured out the issue and we didn't > > >> need any more debugging. And then I sent out [1]. Sorry I missed you > > >> in the cc lise for [1] -- I try to keep track of everyone to cc but > > >> things slip through the cracks sometimes. But at the same time, it's > > >> easy to check for emails from me before saying I didn't help or didn't > > >> send out fixes :) > > >> > > >> If you do try to give [1] a shot, there are a bunch of bugs that > > >> people pointed out for which I gave fixes on top of [1] in the > > >> replies. I was supposed to work on v2 over the holidays, but that > > >> didn't happen because of stuff outside my control. > > >> > > >>> That's ample time to fix this, so I intend to apply this. But I'll > > >>> give it a few days for comments. > > >> > > >> Rob, I'd recommend not applying this because it'll fix it for Dmitry > > >> but break someone else's use case. That's the whole reason it takes me > > >> a while to send out patches -- it's easy to fix it for a subset of > > >> devices, but fixing something without breaking someone else is harder > > >> (I still believe it's doable) and it takes a while to test them on all > > >> the devices I want to test before sending them out. > > > > This case is really simple, I think. Clock controllers (and > > clock-core-framework) are prepared to handle clock orphans properly. > > Moreover they have been supposed to work in such way for quite a while. > > In other words, I don't think we should save them from this > > -EPROBE_DEFERRED. > > A clock controller can depend on other clock controllers for non clock > tree reasons. For example, it might need a clock ON to access its > registers. So, while the CCF can handle orphans properly, that's not > the only dependency. Also, fw_devlink is not just about probing > either. It also has to do with proper sync_state() callbacks. Just a question, please excuse if I'm misunderstanding it. Does fw_devlink created this way also impose any runtime PM dependencies? > > Also, I already fixed the issue you are referring to while not > breaking the conditions I'm referring to. So, I don't know why you are > so opposed to that. See Abel's Tested-by here: > https://lore.kernel.org/lkml/YvonlAwXAoXTUTZe@xxxxxxxxxx/ > > > Thus I think it is better to let them continue doing their job of > > handling probe deferrals on their own, at least for the time being. > > I'm pretty sure your patch will break other Qualcomm platforms because > they depend on sync_state() callbacks to boot up properly when > all/most of their drivers are built as modules. Qualcomm platforms did not use sync state for clock controllers. Only for the icc drivers. > > > And > > then, when your patches are finished, we can think about reenabling > > current behaviour. As a reminder, currently, all Qualcomm platforms > > trying to use double DSI configuration are broken and have to use > > fw_devlink= kernel params. > > I'm/was working on sending out the v2 when I got your email. Hold > tight please. It shouldn't take too long. I'll give v2 a test next week, thank you! -- With best wishes Dmitry
