> -----Original Message----- > From: Menon, Nishanth > Sent: Monday, May 20, 2013 11:34 PM > To: Hiremath, Vaibhav > Cc: Peter Korsgaard; Kevin Hilman; Balbi, Felipe; Paul Walmsley; linux- > omap@xxxxxxxxxxxxxxx; Tony Lindgren > Subject: Re: reset handling in am335x hwmod data > > On 12:47-20130520, Hiremath, Vaibhav wrote: > [...] > > > > > > > > > > > > On 20:10-20130517, Peter Korsgaard wrote: > > > > > > > >>>>> "Kevin" == Kevin Hilman <khilman@xxxxxxxxxx> writes: > > > > > > > > > > > > > > >> In this case, we cannot reset that bank, otherwise > Starter > > > Kit > > > > > > will > > > > > > > >> never boot in mainline. Bad PCB design, I know, but > it's > > > not > > > > > > something > > > > > > > >> we can change now :-) > > > > > > > > > > > > > > Kevin> FWIW, we've seen this before (GPIO connected to > PMIC > > > reset > > > > > is > > > > > > a > > > > > > > Kevin> fun one), and this is why we have > > > > > > omap_hwmod_no_setup_reset(). > > > > > > > > > > > > > > Yes, but there's no dts bindings for this, and from a quick > > > test > > > > > the > > > > > > > reset handling happens before the device tree is probed. > > > > > > I have the same issue with TPS62361 on Palmas -> GPIO > controls > > > the > > > > > > voltage register supplying MPU, without any driver setting > things > > > up, > > > > > > GPIO gets reset and obviously voltage value switches to an > > > voltage > > > > > > where > > > > > > device does not function. > > > > > > > > > > > > Solution I am working on to solve this is [1]: snippet is > part of > > > a > > > > > > patch that I am working on atm. > > > > > > > > > > > > This is the right way to do it IMHO. Will allow the driver to > > > exist > > > > > > when > > > > > > HWMOD will be eventually replaced by some other framework. > > > > > > > > > > > > > > > > > > [1]: http://pastebin.com/XPmAB1Zb > > > > > > > > > > > > > > > > > > > > > > Both seems to be different to me. What we need is to > > > > > Avoid reset of whole GPIO bank during kernel boot. > > > Yes - that is what the above does - as long as the GPIO is > requested > > > and > > > set to the right level by the relevant driver, it is not "unused" > and > > > hence not reset at late_init. > > > > > > > May be I am missing something here, > > > > Isn't _setup_reset() function asserts ocp_reset? And it is > core_initcall. > Hmm.. You are right, I missed that :( > > > > > I am a little unclear as to why this needs to have anything to do > with > > > the precise under-lying mechanism (hwmod or something else). May be > > > "both seem to be different to me" needs a little further > elaboration? > > > > > > > GPIO is connected to the DDR VTT control pin, and we have observed > that > > Due to GPIO bank reset as part of hwmod init during bootup. > > > > > Is this because there is no need for an EMIF driver to handle DDR? > and > > > reset of the GPIO will occur as EMIF is configured at bootloader > and > > > there is no need to do that in kernel, correspondingly there is no > > > "driver" to hold the gpio? > > > > > > > > > > Ideally, it would have been much better if drivers starts > handling > > > > > Idle, ocp reset and standby on their own (killing dependency on > > > hwmod > > > > > init layer). > > > > > > > > > > But looking at current state, > > > > > I agree we need to use DT property here, so how about > > > > > Adding DT property to GPIO node itself. But we have to parse > > > I believe you mean at OMAP specific DT property for hwmod? > > > something like ti,hwmod-no-init-reset? > > > > That’s the idea. > > > > > > > It early during hwmod init stage. We should read all DT nodes > > > > > Inside function __setup() function, that way can get rid of > > > > > HWMOD_INIT_NO_RESET flag completely. Also, this will handle > > > > > Both ocp_reset and domain reset. > > > > > > > > > > > > > Forgot to mention, > > > > > > > > Since this is kernel boot failure issue, I think, > > > > By the time we reach to conclusion, another approach is to > > > > set "HWMOD_INIT_NO_RESET" flag For GPIO0 bank. > > > a) if the GPIO gets moved over to some other GPIO bank on another > > > platform, > > > this wont work > > > > Yes that’s true, but such schematic interface is not recommended. > > And we have not seen any known side-effect of not resetting GPIO0 > bank. > unless you mark the GPIO as taken, another driver could in-adverantly > take over the GPIO and set it to a wrong level (we had a similar story > with LED gpio between Panda Vs Panda-ES). > > > > > > b) for platforms that dont use gpio to hold DDR power, maybe this > is > > > not > > > even relevant and the GPIO bank can safely be reset? > > > > > > > > As I mentioned, there is no known side-effect of not resetting GPIO > bank 0. > It should depend on the platform. > > There are other uses for hwmod-no-reset -> Eg. boot logo displayed by > bootloader - if there is a reset of DSS block and re-configuration, > we'd > notice a blank-out, which is not desirable either. There could be a few > other usage based on no-reset. > > In all cases, you'd prefer to make this: > a) platform dependent (board dts) > b) reserve GPIO as well so that no other driver'd take it - if they > attempt ther'd at least be some form of warning. > Completely agree with you on both the points, and my point and all my comments Were more related to option 'a' above. Thanks, Vaibhav ��.n��������+%������w��{.n�����{�������ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
