Hi, > -----Original Message----- > From: Alexey Klimov [mailto:klimov.linux@xxxxxxxxx] > Sent: Saturday, March 07, 2009 9:42 AM > To: DongSoo(Nathaniel) Kim > Cc: Curran, Dominic; Aguirre Rodriguez, Sergio Alberto; linux- > media@xxxxxxxxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; Sakari Ailus; Tuukka.O > Toivonen; Hiroshi DOYU; MiaoStanley; Nagalla, Hari; Hiremath, Vaibhav; > Lakhani, Amish; Menon, Nishanth > Subject: Re: [PATCH 4/5] OMAP3430SDP: Add support for Camera Kit v3 > > Hello, all > > On Fri, 2009-03-06 at 10:54 +0900, DongSoo(Nathaniel) Kim wrote: > > Hi Alexey, > > > > On Fri, Mar 6, 2009 at 7:05 AM, Alexey Klimov <klimov.linux@xxxxxxxxx> > wrote: > > > Hello, all > > > > > > On Thu, Mar 5, 2009 at 7:42 PM, Curran, Dominic <dcurran@xxxxxx> > wrote: > > >> > > >> Hi Kim > > >> > > >>> -----Original Message----- > > >>> From: linux-omap-owner@xxxxxxxxxxxxxxx [mailto:linux-omap- > > >>> owner@xxxxxxxxxxxxxxx] On Behalf Of DongSoo(Nathaniel) Kim > > >>> Sent: Wednesday, March 04, 2009 8:58 PM > > >>> To: Aguirre Rodriguez, Sergio Alberto > > >>> Cc: linux-media@xxxxxxxxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; Sakari > Ailus; > > >>> Tuukka.O Toivonen; Hiroshi DOYU; MiaoStanley; Nagalla, Hari; > Hiremath, > > >>> Vaibhav; Lakhani, Amish; Menon, Nishanth > > >>> Subject: Re: [PATCH 4/5] OMAP3430SDP: Add support for Camera Kit v3 > > >>> > > >>> Hi Sergio, > > >>> > > >>> > > >>> > > >>> On Wed, Mar 4, 2009 at 5:44 AM, Aguirre Rodriguez, Sergio Alberto > > >>> <saaguirre@xxxxxx> wrote: > > >>> > + /* turn on analog power */ > > >>> > + twl4030_i2c_write_u8(TWL4030_MODULE_PM_RECEIVER, > > >>> > + VAUX_2_8_V, > TWL4030_VAUX2_DEDICATED); > > >>> > + twl4030_i2c_write_u8(TWL4030_MODULE_PM_RECEIVER, > > >>> > + VAUX_DEV_GRP_P1, > TWL4030_VAUX2_DEV_GRP); > > >>> > + > > >>> > + /* out of standby */ > > >>> > + gpio_set_value(MT9P012_STANDBY_GPIO, 0); > > >>> > + udelay(1000); > > >>> > > >>> It seems better using msleep rather than udelay for 1000us much. > Just > > >>> to be safe :) > > >>> How about you? > > >>> > > >> > > >> Why is msleep safer than udelay ? > > > > > > I have small guess that he is wondering why you are using big delays > > > with help of udelay(). (It's may be obvious but as we know udelay uses > > > cpu loops to make delay and msleep calls to scheduler) So, msleep is > > > more flexible and "softer" but if you need precise time or you can't > > > sleep in code you need udelay. Sometimes using udelay is reasonably > > > required. > > > > I totally agree with you. > > But besides the "udelay and mdelay accuracy" issue, Sergio's power up > > timing for MT9P012 seems to delay too much. (not for lens > > controller.) > > I also have experience using MT9P012 sensor with other ISP, but in > > case of mine it took 600 to 800 ms for whole power up sequence. > > But if that delay depends on SDP board and Sergio had no options > > without making delay for that much, then it explains everything. > > So I'm saying if there was no other option than making long delay to > > bring up MT9P012 sensor properly, if I were Sergio I should rather use > > mdelay than udelay. > > I agree with you. mdelay is really safer that udelay. Sorry for not participating much in this thread, I have been busy fixing other comments. This delay setting was set before I ever touched this drivers by other omap3 Linux camera ex-team member here in TI. I suspect they were set to the minimum working level in SDP already, but I haven't honestly tried to move them. I guess it's a good time to do so. :) I'll fix some other things first, and put this on my plate to check before reposting next version of drivers. I really appreciate your feedback on this. Regards, Sergio > > >From file include/linux/delay.h: > > * Using udelay() for intervals greater than a few milliseconds can > * risk overflow for high loops_per_jiffy (high bogomips) machines. The > * mdelay() provides a wrapper to prevent this. For delays greater > * than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture > * specific values can be defined in asm-???/delay.h as an override. > > So, let's Sergio check and decide what he needed! :) > > > Cheers, > > > > Nate > > -- > Best regards, Klimov Alexey > -- 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
