From: Martin Jarman Date: Fri, 10 Oct 2008 13:40:31 +0100 Subject: [U-Boot] Special memory test Question References: <000801c929c5$01d37060$4201a8c0@amil><20081010133210.310287e6@hskinnemo-gx745.norway.atmel.com> <20081010134329.6ddcce09@hskinnemo-gx745.norway.atmel.com> Message-ID: <004b01c92ad5$63ce87d0$4201a8c0@amil> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de ----- Original Message ----- From: "Haavard Skinnemoen" To: "Martin Jarman" Cc: Sent: Friday, October 10, 2008 12:43 PM Subject: Re: [U-Boot] Special memory test Question > Haavard Skinnemoen wrote: >> to start at physical address zero and scribble over the entire physical >> address range of the processor until it eventually tries to access an >> invalid physical address and gets a bus error exception. > > Actually, that's wrong. It won't scribble over anything since it only > does reads. But it will access an invalid address and get a bus error > exception eventually. > >> Nope, it's a user error. Try running this command instead: >> >> loop.b 10400000 4 >> >> It's been running on my board for several minutes without crashing. > > Btw, that command won't actually test the SDRAM since do_mem_loop() > accesses cacheable memory. The first access will load the data into the > dcache, and subsequent accesses will simply read it from the dcache and > not cause any memory accesses. > > What is this command supposed to test anyway? It's highly unlikely that > it will find any SDRAM problems by simply reading an address without > checking the result... > > Haavard Thank you for your replies, and I accept my 'user error' (head hung in shame) and can confirm the test appears to run correctly when called with the proper arguments. I note Wolfgang has answered your question about what the test is for. best regards Martin Jarman