On 06/25/2013 08:27 AM, Linus Walleij wrote: > On Fri, Jun 21, 2013 at 11:17 PM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > >> When I pushed for the concept of groups, I intended it to mean precisely >> one single thing. The points below describe this. >> >> 1) A pin is a single pin/ball/pad on the package. >> >> 2) Some register fields affect just a single pin. For example, there may >> be a register field that affects pin A8's mux setting only. >> >> 3) Some register fields affect multiple pins at once. For example, >> perhaps one register field affects both pin A8's an pin A7's mux setting >> at once. >> >> 4) Depending on HW design, all register fields might be of type >> described at (2) above, or all of the type described at (3) above, or a >> mixture of both. Tegra is a mixture. >> >> 5) I expect the concept of a pin group to solely represent the various >> groups of pins affected by each register field; in (2) above one pin per >> group, in (3) above many pins per group. >> >> Thus, to my mind, a pin group is purely a HW concept, and dictated >> purely by HW design. > > This we can discuss perpetually it seems. > > For Nomadik, as I've pointed out in the past it is actually: > > (6): it is one register/set if bits per pin, BUT the register settings > pertain to physical lines having electrical settings which postulate > that they be handled in batch or wreak havoc. > > I.e. it is a HW limitation in the *silicon* of *all* implementations, > but that is *not* expressed in the register map. > > For the practical consequences see __nmk_config_pins if (glitch) > runpath. Handling this as a group makes perfect sense from > a hardware point of view. OK, so there are certainly some HW designs that may benefit from using groups even where the registers are per-pin. Using them there makes sense. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
