From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Date: Mon, 22 Dec 2014 14:34:24 +0000 Subject: [U-Boot] [PATCH 11/14] sunxi: Fill memory before comparing it when doing dram init on sun6i In-Reply-To: <20141222163219.2ed527c7@i7> References: <1418761900-14035-1-git-send-email-hdegoede@redhat.com> <1418761900-14035-11-git-send-email-hdegoede@redhat.com> <1418929933.26985.106.camel@hellion.org.uk> <54945890.1020708@redhat.com> <1419257960.26985.186.camel@hellion.org.uk> <20141222163219.2ed527c7@i7> Message-ID: <1419258864.26985.187.camel@hellion.org.uk> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Mon, 2014-12-22 at 16:32 +0200, Siarhei Siamashka wrote: > On Mon, 22 Dec 2014 14:19:20 +0000 > Ian Campbell wrote: > > > On Fri, 2014-12-19 at 17:55 +0100, Hans de Goede wrote: > > > Hi, > > > > > > On 18-12-14 20:12, Ian Campbell wrote: > > > > On Tue, 2014-12-16 at 21:31 +0100, Hans de Goede wrote: > > > >> The sun8i boot0 code fills the DRAM with a "random" pattern before comparing > > > >> it at different offsets to do columns, etc. detection. The sun6i boot0 code > > > >> does not do it, but it seems like a good idea to do this regardless. > > > > > > > > Is this the right way round? > > > > > > Yes, while working on the sun8i code I noticed that it was prefilling memory > > > before doing wrap-around checks like the sun6i code is doing too, and then I > > > realized that the sun6i code was relying on whatever is in DRAM being random > > > enough for its wrap-around tests to work, without ensuring it is random > > > enough. > > > > > > > The existing sun6i code (which you are > > > > moving here) seems to _rely_ on something having written a useful > > > > pattern, which I would have assumed to have been boot0. Or else how does > > > > it work now? Chance? > > > > > > Yep, it purely works by chance so far. > > > > "excellent". Can you mention that in the commit message please. With > > that: Acked-by: Ian Campbell > > Ian, are you fine with the fact that it still works by chance > even after this "fix"? Albeit with a much higher chance of not > running into troubles. Yes, it's clearly an improvement even if it isn't perfect. Ian.