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. Gražvydas -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
