On Wed, Mar 3, 2021 at 5:24 PM Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> wrote: > > On Wed, 2021-03-03 at 16:20 +0100, Benjamin Gaignard wrote: > > Le 03/03/2021 à 15:17, Philipp Zabel a écrit : > > > Hi Benjamin, > > > > > > On Mon, 2021-03-01 at 16:17 +0100, Benjamin Gaignard wrote: > > > > The two VPUs inside IMX8MQ share the same control block which can be see > > > > as a reset hardware block. > > > This isn't a reset controller though. The control block also contains > > > clock gates of some sort and a filter register for the featureset fuses. > > > Those shouldn't be manipulated via the reset API. This driver is very similar to several other patches for clk_blk control [1] which contain both resets and clock-enables on the i.MX8MP, i.MX8MM and i.MX8MN. In those cases, there are some specific power domain controls that are needed, but I wonder if the approach to creating resets and clock enables could be used in a similar way if the IMX8MQ doesn't have the same quirks. In the case of the i.MX8M Mini, I think it has the same VPU. [1] - https://patchwork.kernel.org/project/linux-clk/patch/1599560691-3763-12-git-send-email-abel.vesa@xxxxxxx/ adam > > > > They are all part of the control block and of the reset process for this > > hardware that why I put them here. I guess it is border line :-) > > I'm pushing back to keep the reset control framework focused on > controlling reset lines. Every side effect (such as the asymmetric clock > ungating) in a random driver makes it harder to reason about behaviour > at the API level, and to review patches for hardware I am not familiar > with. > > > > > In order to be able to add the second VPU (for HECV decoding) it will be > > > > more handy if the both VPU drivers instance don't have to share the > > > > control block registers. This lead to implement it as an independ reset > > > > driver and to change the VPU driver to use it. > > > Why not switch to a syscon regmap for the control block? That should > > > also allow to keep backwards compatibility with the old binding with > > > minimal effort. > > > > I will give a try in this direction. > > Thank you. > > > > > Please note that this series break the compatibility between the DTB and > > > > kernel. This break is limited to IMX8MQ SoC and is done when the driver > > > > is still in staging directory. > > > I know in this case we are pretty sure there are no users of this > > > binding except for a staging driver, but it would still be nice to keep > > > support for the deprecated binding, to avoid the requirement of updating > > > kernel and DT in lock-step. > > > > If I want to use a syscon (or a reset) the driver must not ioremap the "ctrl" > > registers. It means that "ctrl" has to be removed from the driver requested > > reg-names (imx8mq_reg_names[]). Doing that break the kernel/DT compatibility. > > Somehow syscon and "ctrl" are exclusive. > > The way the driver is set up currently, yes. You could add a bit of > platform specific probe code, though, that would set up the regmap > either by calling > syscon_regmap_lookup_by_phandle(); > for the new binding, or, if the phandle is not available, fall back to > platform_get_resource_byname(..., "ctrl"); > devm_ioremap_resource(); > devm_regmap_init_mmio(); > for the old binding. > The actual codec .reset and variant .runtime_resume ops could be > identical then. > > regards > Philipp > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
