* Paul Walmsley <paul@xxxxxxxxx> [110702 17:58]: > On some boards, it's not possible to reset certain IP blocks during > kernel initialization. Some boards connect GPIO lines to external > voltage controllers, so resetting them may cause voltage to drop on a > critical supply[1]. Other boards connect GPIO lines to reset pins on > external devices without open documentation, so if the GPIO blocks are > reset, the external devices cannot currently be reconfigured[2]. > > The correct way to fix these issues on OMAP is to add a > hwmod_no_setup_reset(hwmod) call to the board file, that references > the IP block that must preserve its state. This allows the OMAP core > code to reset the remaining IP blocks. > > However, during initial bring-up of a new board, it may be desirable > to not reset any IP block, for ease of debugging. This patch adds a > kernel command line parameter, 'hwmod_no_setup_reset', that prevents > the OMAP hwmod code from resetting any IP block during init. > > 1. Nayak, Rajendra. _[PATCH 7/7] 4460sdp/blaze/panda: hwmod: Prevent > gpio1 reset during hwmod init_. 1 July 2011. E-mail to the > linux-omap@xxxxxxxxxxxxxxx mailing list. Retrieved from > http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg51992.html > > 2. Buesch, Michael. _Nokia n810 LCD (MIPID/blizzard) on 2.6.38_. 28 > Feb 2011. E-mail to the linux-omap@xxxxxxxxxxxxxxx mailing list. > Retrieved from http://www.spinics.net/lists/linux-omap/msg47277.html Also related is the gptimer12 on secure omaps as reported by Aaro. > + hwmod_no_setup_reset > + [OMAP] During kernel initialization, > + prevent the subarchitecture code from resetting > + IP blocks before the driver loads. Useful for > + initial bring-up of boards which require some > + bootloader configuration to be retained on GPIO or > + other IP blocks. > + How about just make it hwmod_reset=1 with 0 being the default value for now? Regards, Tony -- 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
