From mboxrd@z Thu Jan 1 00:00:00 1970 From: S. Egbert Date: Tue, 07 Feb 2006 20:45:57 -0800 Subject: [U-Boot-Users] u-boot kernel parameters In-Reply-To: <20060207205436.974293525D0@atlas.denx.de> References: <20060207205436.974293525D0@atlas.denx.de> Message-ID: <43E97785.9020001@sbcglobal.net> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de > >> 4. Make heavy use of on-board LED indicators by calling ioremap() and >> poking your virtualized hardware register location to flip on the LED >> indicators. > > I strongly recommend *against* doing this, at least unless you know > *exactly* what you are doing (and then you don't need this because > you will use a BDI2000 anyway). I've seen to many reports of "Linux > crashes when enabling the MMU" that were cause by exactly such > attempts. > Oh yeah... I totally agreed on your recommendation. But when one is located FAR FAR AWAY from the cushy software laboratory and without a hardware debugger, I have find this technique extremely useful in very DARK, DARK circumstances. Another time, I had to bring-up a custom board that is totally devoid of inputs/output interface (as those interfaces were still under HW development), this LED method saved my bacon as I SLOWLY and PAINFULLY integrate Xilinx UARTLITE driver (if one is extremely careful about setting aside a TLB region JUST for that purpose. Alright, alright.... Let us call this LED indicators, a 'poor man's' debugger. Desperate acts calls for desperate measure.