On Tue, May 28, 2019 at 4:11 AM Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: > > Hi, > > On 10/05/2019 22:42, Adam Ford wrote: > > Currently the source code is compiled using hard-coded values > > from CONFIG_OMAP2_DSS_MIN_FCK_PER_PCK. This patch allows this > > clock divider value to be moved to the device tree and be changed > > without having to recompile the kernel. > > > > Signed-off-by: Adam Ford <aford173@xxxxxxxxx> > > I understand why you want to do this, but I'm not sure it's a good idea. > It's really something the driver should figure out, and if we add it to > the DT, it effectively becomes an ABI. > > That said... I'm not sure how good of a job the driver could ever do, as > it can't know the future scaling needs of the userspace at the time it > is configuring the clock. And so, I'm not nacking this patch, but I > don't feel very good about this patch... > > The setting also affects all outputs (exluding venc), which may not be > what the user wants. Then again, I think this setting is really only > needed on OMAP2 & 3, which have only a single output. But that's the > same with the current kconfig option, of course. > > So, the current CONFIG_OMAP2_DSS_MIN_FCK_PER_PCK is an ugly hack, in my > opinion, and moving it to DT makes it a worse hack =). But I don't have > any good suggestions either. As it stands the Logic PD OMAP35 and AM37/DM37 boards (SOM-LV and Torpedo) require this to be hard coded to 4 or it hangs during start. This is the case for all versions 4.2+. I haven't tested it with older stuff. Tony has a DM3730 Torpedo kit and reported the hanging issue to me. I told him to set that value to 4 to make it not hang. He asked that I move it to the DT to avoid custom kernels. I agree it's a hack, but if it's create a customized defconfig file for 4 boards or modify the device tree, it seems like the device tree approach is less intrusive. adam > > Tomi > > -- > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
