From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Tue, 17 Nov 2015 09:05:22 +0100 Subject: [U-Boot] [PATCH] ARM: mxs: fix VDDD brownout setting In-Reply-To: <3136450.3uu2P0VBkS@kerker> References: <1447624032-16503-1-git-send-email-mhei@heimpold.de> <201511161201.36280.marex@denx.de> <3136450.3uu2P0VBkS@kerker> Message-ID: <201511170905.22657.marex@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Monday, November 16, 2015 at 08:47:38 PM, Michael Heimpold wrote: > Hi Marek, Hi! > Am Monday 16 November 2015, 12:01:36 schrieben Sie: > > On Sunday, November 15, 2015 at 10:47:12 PM, Michael Heimpold wrote: > > > At the moment, the desired brownout is at 1.0V. However, > > > this setting cannot be realized by hardware since we have > > > only 3 bits to represent the voltage difference from the > > > target value. > > > > > > Target value is 1500 mV, brownout target is 1000 mV, > > > voltage steps are 25 mV. > > > > > > Register content calculation: > > > (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14 > > > > > > Register takes only 3 bits, that is 0x4. > > > > > > But 0x4 * 25 [mV] = 100 [mV], that means that actual > > > brownout level is 1500 [mV] - 100 [mV] = 1.4 V. > > > > > > Minimum possible BO level is > > > > > > 1500 [mV] - 0x7 * 25 [mV] = 1315 [mV]. > > > > > > So lets use this value as desired BO value (which is > > > also the same as FSL bootlets use). > > > > > > Signed-off-by: Michael Heimpold > > > Cc: Marek Vasut > > > Cc: Otavio Salvador > > > Cc: Fabio Estevam > > > > Uh, nice find. How did you find it? > > I was investigating a boot stall with I2SE's Duckbill devices and since > we're about to switch from FSL bootlets to U-Boot, I compared the register > settings. Then I stumbled about the comment and wondered whether > 1.0V BO level makes sense for 1.5V target voltage... Heh, nice. Thanks! Best regards, Marek Vasut