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. >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-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
