Hi, On Wed, Aug 12, 2020 at 01:47:42PM +0300, Tomi Valkeinen wrote: > Hi Guido, > > On 12/08/2020 11:39, Guido Günther wrote: > > Hi, > > On Thu, Aug 06, 2020 at 01:34:29PM +0200, Swapnil Jakhade wrote: > >> This patch series adds new DRM bridge driver for Cadence MHDP DPI/DP > >> bridge. The Cadence Display Port IP is also referred as MHDP (Mobile High > >> Definition Link, High-Definition Multimedia Interface, Display Port). > >> Cadence Display Port complies with VESA DisplayPort (DP) and embedded > >> Display Port (eDP) standards. > > > > Is there any relation to the cadence mhdp ip core used inthe imx8mq: > > > > https://lore.kernel.org/dri-devel/cover.1590982881.git.Sandor.yu@xxxxxxx/ > > > > It looks very similar in several places so should that use the same driver? > > Cheers, > > -- Guido > > Interesting. > > So the original Cadence DP patches for TI SoCs did create a common driver with Rockchip's older mhdp > driver. And looks like the IMX series points to an early version of that patch ("drm/rockchip: > prepare common code for cdns and rk dpi/dp driver"). > > We gave up on that as the IPs did have differences and the firmwares used were apparently quite > different. The end result was very difficult to maintain, especially as (afaik) none of the people > involved had relevant Rockchip HW. Is the `struct mhdp_platform_ops` a leftover from that? Can that be dropped? > The idea was to get a stable DP driver for TI SoCs ready and upstream, and then carefully try to > create common parts with Rockchip's driver in small pieces. I wonder how imx8 would best blend into this? First thing will likely be to upstream the phy code in driveres/phy/ so a modified version of this bridge driver could call into that, then go and look for common patterns. > If the Rockchip and IMX mhdp have the same IP and same firmware, then they obviously should share > code as done in the series you point to. I'm pretty sure they use different firmware though - the imx8mq additionally supports HDMI with a different firmware on the same IP core (13.4 and 13.5 in the imx8mq ref manual). > Perhaps Cadence can clarify the differences between IMX, TI and > Rockchip IPs and FWs? That would be great! -- Guido > I'm worried that if there are IP differences, even if not great ones, and if the FWs are different > and developed separately, it'll be a constant "fix X for SoC A, and accidentally break Y for SoC B > and C", especially if too much code is shared. > > In the long run I'm all for a single driver (or large shared parts), but I'm not sure if we should > start with that approach. > > Tomi > > -- > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki >
