From mboxrd@z Thu Jan 1 00:00:00 1970 From: olof@lixom.net (Olof Johansson) Date: Tue, 22 Dec 2015 11:22:52 -0800 Subject: [PATCH v5] bus: uniphier-system-bus: add UniPhier System Bus driver In-Reply-To: <1449643979-27329-1-git-send-email-yamada.masahiro@socionext.com> References: <1449643979-27329-1-git-send-email-yamada.masahiro@socionext.com> Message-ID: <20151222192252.GO30172@localhost> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Dec 09, 2015 at 03:52:59PM +0900, Masahiro Yamada wrote: > The UniPhier System Bus is an external bus that connects on-board > devices to the UniPhier SoC. Each bank (chip select) is dynamically > mapped to the CPU-viewed address base via the bus controller. The > bus controller must be configured before any access to the bus. > > This driver parses the "ranges" property of the System Bus node and > initialized the bus controller. After the bus becomes ready, devices > below it are populated. > > Note: > Each bank can be mapped anywhere in the supported address space; > there is nothing preventing us from assigning bank 0 on 0x42000000, > 0x43000000, or anywhere as long as such region is not used by others. > So, the "ranges" is just one possible software configuration, which > does not seem to fit in device tree because device tree is a hardware > description language. However, of_translate_address() requires > "ranges" in every bus node between CPUs and device mapped on the CPU > address space. In other words, "ranges" properties must be statically > defined in device tree. After some discussion, I decided the dynamic > address reassignment by the driver is too bothersome. Instead, the > device tree should provide a reasonable translation setup that the OS > can rely on. > > Signed-off-by: Masahiro Yamada > Acked-by: Rob Herring > Acked-by: Arnd Bergmann Thanks, applied to next/drivers. -Olof