________________________________________ From: Sonasath, Moiz Sent: Tuesday, February 02, 2010 3:40 PM To: Tony Lindgren; Pais, Allen Cc: linux-omap@xxxxxxxxxxxxxxx Subject: RE: [PATCH 1/2] omap: Disable GAIA I2C1/I2C4 internal pull-ups Tony/Allen/Paul, > -----Original Message----- > From: linux-omap-owner@xxxxxxxxxxxxxxx [mailto:linux-omap- > owner@xxxxxxxxxxxxxxx] On Behalf Of Tony Lindgren > Sent: Tuesday, February 02, 2010 10:56 AM > To: Pais, Allen > Cc: linux-omap@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/2] omap: Disable GAIA I2C1/I2C4 internal pull-ups > > * Pais, Allen <allen.pais@xxxxxx> [100201 18:56]: > > > > ________________________________________ > > From: Tony Lindgren [tony@xxxxxxxxxxx] > > Sent: Monday, February 01, 2010 7:53 PM > > To: Pais, Allen > > Cc: linux-omap@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH 1/2] omap: Disable GAIA I2C1/I2C4 internal pull-ups > > > > Hi, > > > > * Pais, Allen <allen.pais@xxxxxx> [100121 02:31]: > > > From 4044fcc9c517e86fbea9f7d3b15d5cf75a767476 Mon Sep 17 00:00:00 2001 > > > From: Allen Pais <allen.pais@xxxxxx> > > > Date: Thu, 21 Jan 2010 21:00:04 +0530 > > > Subject: [PATCH 1/2] omap: Disable GAIA I2C1/I2C4 internal pull-ups > > > > > > This patch disables GAIA I2C1 adn I2C4(SR) internal pull-up, to > > > use only the external HW resistor >=470 Ohm for the assured > > > functionality in HS mode. > > > > > > While testing the I2C in High Speed mode, it was discovered that > > > without a proper pull-up resistor, there is data corruption during > > > multi-byte transfer. RTC(time_set) test case was used for testing. > > > > > > From the analysis done, it was concluded that ideally we need a > > > pull-up of 1.6k Ohm(recomended) or atleast 470 Ohm or greater for > > > assured performance in HS mode. > > > > Does this apply to 3630 only, or also 34xx? Is this safe to do > > always? > > > > [Allen] Yes, it does apply to 36xx only. There is some confusion, this patch holds true for all OMAP34XX, 36XX as well as 44XX. The idea was to rely on only external Pull-up for I2C operation and disable any internal pull-up on any of the connected power IC's: Triton(TWL4030)/GAIA(TWL5030)/Phoenix(TWL6030) [Allen] sorry about the confusion. I mistook it for the other patch. I did verify, the register 'REG_GPPUPDCTR1' holds true for Triton(TWL4030)/GAIA(TWL5030), hence for OMAP34XX/36XX. But there is a register change for this PU/PD control on Phoenix(TWL6030) which is used with OMAP44XX. So I might have to modify this patch a little as this code will apply for TWL4030/5030 and have to introduce new code to achieve the intended fix for TWL6030. The second patch of the series: 'omap: 3630: Disable internal pull-ups' applies only for OMAP36XX as it is a new feature introduced in OMAP3630. I have to check if that feature is available on OMAP44XX as well, if so I will modify that patch to extend to OMAP44XX in future. Although > > Sounds like then this configuration should be passed from the > board-*.c file in platform_data as the external pulls depend > on the board. > > > BTW, once ready it hould be sent to Samuel Ortiz with linux-omap > > list Cc'd: > > > > [Allen] i'll have it sent to Samuel also. > > Thanks, we can't merge it yet though, see above. > > 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 Regards Moiz Sonasath -- 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
