aboutsummaryrefslogtreecommitdiff
path: root/docs/system/arm/vexpress.rst
AgeCommit message (Collapse)Author
2023-11-06hw/arm/vexpress-a9: Remove useless mapping of RAM at address 0Peter Maydell
On the vexpress-a9 board we try to map both RAM and flash to address 0, as seen in "info mtree": address-space: memory 0000000000000000-ffffffffffffffff (prio 0, i/o): system 0000000000000000-0000000003ffffff (prio 0, romd): alias vexpress.flashalias @vexpress.flash0 0000000000000000-0000000003ffffff 0000000000000000-0000000003ffffff (prio 0, ram): alias vexpress.lowmem @vexpress.highmem 0000000000000000-0000000003ffffff 0000000010000000-0000000010000fff (prio 0, i/o): arm-sysctl 0000000010004000-0000000010004fff (prio 0, i/o): pl041 (etc) The flash "wins" and the RAM mapping is useless (but also harmless). This happened as a result of commit 6ec1588e in 2014, which changed "we always map the RAM to the low addresses for vexpress-a9" to "we always map flash in the low addresses", but forgot to stop mapping the RAM. In real hardware, this low part of memory is remappable, both at runtime by the guest writing to a control register, and configurably as to what you get out of reset -- you can have the first flash device, or the second, or the DDR2 RAM, or the external AXI bus (which for QEMU means "nothing there"). In an ideal world we would support that remapping both at runtime and via a machine property to select the out-of-reset behaviour. Pending anybody caring enough to implement the full remapping behaviour: * remove the useless mapped-but-inaccessible lowram MR * document that QEMU doesn't support remapping of low memory Fixes: 6ec1588e ("hw/arm/vexpress: Alias NOR flash at 0 for vexpress-a9") Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1761 Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20231103185602.875849-1-peter.maydell@linaro.org
2021-02-08docs/system: document an example vexpress-a15 invocationAlex Bennée
The wiki and the web are curiously absent of the right runes to boot a vexpress model so I had to work from first principles to work it out. Use the more modern -drive notation so alternative backends can be used (unlike the hardwired -sd mode). Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Cc: Anders Roxell <anders.roxell@linaro.org> Message-Id: <20210202134001.25738-15-alex.bennee@linaro.org>
2020-05-21docs/system: Document Arm Versatile Express boardsPeter Maydell
Provide a minimal documentation of the Versatile Express boards (vexpress-a9, vexpress-a15). Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Message-id: 20200507151819.28444-4-peter.maydell@linaro.org