linux-kernel - RE: [PATCH 2/2] rtc-tps65910: enable RTC power domain on initialization

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <A874F61F95741C4A9BA573A70FE3998F6418F30B@DQHE02.ent.ti.com>
Date:	Thu, 29 Nov 2012 23:11:37 +0000
From:	"Kim, Milo" <Milo.Kim@...com>
To:	Venu Byravarasu <vbyravarasu@...dia.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	"a.zummo@...ertech.it" <a.zummo@...ertech.it>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	Sivaram Nair <sivaramn@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/2] rtc-tps65910: enable RTC power domain on
 initialization

Hi Venu

> >  Enabling RTC HW block depends on the default value of TPS65910
> register.
> >  In some mode, RTC block is disabled by default.(eg. AM3517
> Craneboard)
> >  In this case, RTC_PWDN(RTC power down) bit should be cleared to
> enable
> >  the RTC HW block.
> 
> From the description of RTC_PWDN bit of DEVCTRL_REG in TPS65910 data
> sheet
> it is very evident that the default value of RTC_PWDN is 0.

According to the datasheet(http://www.ti.com/lit/ds/swcs046q/swcs046q.pdf),
the default value RTC_PWDN is 1 which means power down.

The default values are loaded from the EEPROM with BOOT_MODE 0,1 pin connection.
The RTC is disabled by default when BOOT_MODE = 00.
The Craneboard has the BOOT_MODE 00.

You may have other EEPROM settings,
however the official datasheet shows the RTC block is off by default.

Could you check the silicon version number? (0x80 register - JTAGVERNUM_REG)
In my case, the read value is 0x01.

> Probably on "AM3517 Craneboard", some code is running prior to the RTC
> driver
> which might be writing 1 on to this bit. IMO you must disable that
> write operation
> instead of just writing default value into a register.

Thank you for your comment.
I've read the DEVCTRL register (0x3F) in mfd tps65910 driver
as soon as the regmap registration is done, however RTC_PWDN is always 1.
That means the RTC is disabled by default.

Best Regards,
Milo

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/