Messages in this thread | | | Date | Mon, 20 Aug 2012 14:51:48 +0200 | From | Thomas Petazzoni <> | Subject | Re: [PATCH 01/11] pinctrl: mvebu: pinctrl driver core |
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Hello,
Le Mon, 20 Aug 2012 11:46:14 +0200, Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com> a écrit :
> >> +uart1: serial@12100 { > >> + compatible = "ns16550a"; > >> + reg = <0x12100 0x100>; > >> + reg-shift = <2>; > >> + interrupts = <7>; > >> + clock-frequency = <166666667>; > > > > It's got nothing to do with this patch, but getting a clock frequency > > out of the DT instead of getting it from the clk_get_rate(clk) and > > the clock tree seems absurd... (But maybe this platform does not > > even have a clk implementation?) > > It's of_serial's implementation. I patched that once for getting > frequency out of "clocks" property but then I got busy with > porting mach-dove and pinctrl.. Marvell SoCs do have a clk > implementation and as soon as of_serial can handle "clocks" > property it will be used for sure. I can remove "clock-frequency" > from the example anyway as it is not really part of pinctrl > binding documentation.
We are also working on using the clk framework for the 370/XP support (my colleague Grégory in Cc has started working on this last week), and we also want to be able to get the serial clock-frequency from the clk framework instead of an explicit value in the DT node. But that's a separate topic :)
> > Is it possible to use devm_* managed devm_kzalloc() for this map > > so you don't need to free it explicitly? > > > > (Maybe not, just checking.) > > Hmm, I guess not as I thought I've read not to use devm_kfree when > you allocate _and_ free stuff on runtime without removing the device > itself, right?
It is also my understanding that devm_*() functions should be used to allocate things that should persist until the device is removed. But I might be wrong here.
> >> +struct mvebu_mpp_ctrl { > >> + const char *name; > >> + u8 pid; > >> + u8 npins; > > > > So, there will never be > 256 pins on a Marvell platform? > > Well, with all current platforms we are well below 100. I guess > 256 max (muxable) pins will be enough.
Agreed, and this structure is completely internal to the kernel, so we can easily change it in the future if needed.
> >> + * struct mvebu_mpp_ctrl_setting - describe a mpp ctrl setting > >> + * @val: ctrl setting value > > > > It is not obvious to me what this means, it it possible to elaborate > > on how this member is defined and used? > > Well, I see if I can clarify the description but wrt the datasheet it > _should_ be quite obvious.
I think the setting/function/group/control terminology would benefit from an explanation, as it isn't very easy to figure out what all these words mean in the context of the pinctrl-mvebu driver.
> In some internal review with Andrew I also added a spinlock to > mvebu_pinconf_get/_set that will protect all calls to generic and specific > _get/_set register accesses. Moreover, I replaced clk_get_sys in pinctrl-dove > with the devm_ counterpart and removed the explicit clk_put.
Yes, I had seen this discussion, but I am not sure it is needed: it seems the pinctrl core calls all the pinconf_set/pinconf_get methods with the pinctrl_mutex held. When I wrote an initial pinctrl driver for 370/XP I had the same question as Andrew and my conclusion was that the locking done by the pinctrl subsystem core was sufficient.
Best regards,
Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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