On Tue, Sep 29, 2020 at 02:01:44PM -0700, Matt Roper wrote: > On Tue, Sep 29, 2020 at 11:30:22PM +0300, Ville Syrjälä wrote: > > On Tue, Sep 29, 2020 at 08:20:22PM +0000, Souza, Jose wrote: > > > On Tue, 2020-09-29 at 23:02 +0300, Ville Syrjälä wrote: > > > > On Tue, Sep 29, 2020 at 07:33:45PM +0000, Souza, Jose wrote: > > > > > On Tue, 2020-09-29 at 17:41 +0530, Tejas Upadhyay wrote: > > > > > > JSL has update in vswing table for eDP > > > > > > > > > > Would be nice to mention in the commit description why PCH is being used, that would avoid Ville's question. > > > > > > > > If the thing has nothing to do PCH then it should not use the PCH type > > > > for the the check. Instead we should just do the EHL/JSL split. > > > > > > In the first version Matt Roper suggested to use PCH to differentiate between EHL and JSL, Jani also agreed with this solution.This 2 PCHs can only be > > > associate with EHL and JSL respectively, so no downsides here. > > > > The downside is that the code makes no sense on the first glance. > > It's going to generate a "wtf?" exception in the brain and require > > me to take a second look to figure what is going on. Exception > > handling is expensive and shouldn't be needed in cases where it's > > trivial to make the code 100% obvious. > > The bspec documents EHL and JSL as being the same platform and identical > in all programming since they are literally the same display IP; this > vswing table is the one and only place where the two are treated in a > distinct manner for reasons that lie outside the display controller. If > you had to stop and take a closer look at the code here, that's a > probably a good thing since in general there should generally never be a > difference in the behavior between the two. Adding an additional > clarifying comment is probably in order too since this is a very > exceptional special case. > > If we deviate from the bspec's guidance and try to split IS_ELKHARTLAKE > and IS_JASPERLAKE across the whole driver, that's going to be a lot more > pain to maintain down the road since we'll almost certainly have cases > where someone silently leaves one or the other off a condition and gets > unexepcted behavior. I could see arguments for using a SUBPLATFORM here > like we do for TGL_U vs TGL_Y, but even that seems like overkill if we > already have a clear way to distinguish the two cases (PCH pairing) and > can just leave a clarifying comment. That fixed PCH pairing is totally undocumented AFAICS. And vswing has nothing to do with the south display, so the wtf will still happen. Comment or no comment. -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
