* Grazvydas Ignotas <notasas@xxxxxxxxx> [141114 06:38]: > On Fri, Nov 14, 2014 at 1:58 AM, Tony Lindgren <tony@xxxxxxxxxxx> wrote: > > * Paul Walmsley <paul@xxxxxxxxx> [141113 15:01]: > >> Hi > >> > >> On Thu, 13 Nov 2014, Tony Lindgren wrote: > >> > >> > * Tomi Valkeinen <tomi.valkeinen@xxxxxx> [141113 03:33]: > >> > > On 12/11/14 17:02, Tony Lindgren wrote: > >> > > > >> > > >> And, with a quick grep, I see CONTROL_DEVCONF1 touched in multiple > >> > > >> places in the kernel. I wonder if adding a pinmux entry for it could > >> > > >> cause some rather odd problems. > >> > > > > >> > > > They can all use pinctrl-single no problem. > >> > > > >> > > Can, but don't. That's my worry. If we touch the DEVCONF1 via pinmux, > >> > > and we have code in mach-omap2 that also touch DEVCONF1, without any > >> > > knowledge (and locking) between those... > >> > > >> > Hmm yeah the McBSP clock mux could be racy as the mux register for > >> > McBSP is treated as a clock. This register muxes the clock between > >> > external pin and internal clock. Considering that this should be > >> > selectable at board level as the external clock probably needs to be > >> > used if level shifters are being used, it should be really handled by > >> > pinctrl-single. > >> > > >> > The other use for hsmmc.c and pdata-quirks.c for the one time mux for > >> > MMC clock from the MMC clock pin. That can be done with pinctrl-single > >> > from the MMC driver too for DT based booting. > >> > > >> > Then we just have the save and restore of the registers for > >> > off-idle. > >> > > >> > > So _maybe_ that's not an issue, as the pinmux config we have here is > >> > > fixed, and done once at boot time, and maybe the code in mach-omap2 that > >> > > touch DEVCONF1 is also ran just once and not at the same time as the > >> > > pinmux. But I don't know if that's so. > >> > > >> > It seems we could just do a read-only check for McBSP in the clock > >> > code for the mux register, or even completely drop that code from > >> > cclock3xxx_data.c and start using the pinctrl for that mux. > >> > > >> > Paul & Tero, got any comments here? > >> > >> It's best to move all of the SCM register reads/writes to an SCM IP block > >> driver. This driver would be the only entity that would touch the SCM IP > >> block registers - no other code on the system would touch it (perhaps > >> aside from anything needed for early init). The SCM driver would enforce > >> mutual exclusion via a spinlock, so concurrent SCM register modifications > >> wouldn't flake out. Then the SCM driver would register clocks with the > >> CCF, register pins with the pinctrl subsystem, etc. etc. > > > > We actually do have that with pinctrl-single + syscon. We certainly > > need to implement more Linux framework drivers for the SCM registers. > > Things like regulators, clocks, and PHYs, but they should use > > pinctrl-single + syscon. See the the pbias-regulator.c for example. > > > > Looking at the McBSP clock handling, threre's yet more handling of > > the same DEVCONF1 mux register in omap2_mcbsp_set_clks_src that gets > > alled from omap_mcbsp_dai_set_dai_sysclk. > > > > To me it seems that if we handle the DEVCONF with pinctrl-single, we > > don't need most of the McBSP fck code or the omap2_mcbsp_set_clks_src. > > Having the mux register as the clock enable register is not nice.. > > Who knows what the clock coming from the external pin might be :) > > How will audio do dynamic muxing without that code? > The pin must be remuxed back to internal clock when audio stops, or > else PM breaks. There's a standard way of dealing with that already available. We can just have runtime_pm functions call pinctrl_pm_select_sleep_state() and pinctrl_pm_select_default_state(). Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
