From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Wed, 25 Mar 2015 12:53:39 +0100 Subject: [U-Boot] [PATCH 2/3] ARM: bcm2835: implement phys_to_bus/bus_to_phys In-Reply-To: <1427249255-27427-2-git-send-email-swarren@wwwdotorg.org> References: <1427249255-27427-1-git-send-email-swarren@wwwdotorg.org> <1427249255-27427-2-git-send-email-swarren@wwwdotorg.org> Message-ID: <201503251253.39949.marex@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Wednesday, March 25, 2015 at 03:07:34 AM, Stephen Warren wrote: > The BCM283[56] contain both a L1 and L2 cache between the GPU (a/k/a > VideoCore CPU?) and DRAM. DMA-capable peripherals can also optionally > access DRAM via this same L2 cache (although they always bypass the L1 > cache). Peripherals select whether to use or bypass the cache via the > top two bits of the bus address. > > An IOMMU exists between the ARM CPU and the rest of the system. This > controls whether the ARM CPU's accesses use or bypass the L1 and/or L2 > cache. This IOMMU is configured/controlled exclusively by the VideoCore > CPU. > > In order for DRAM accesses made by the ARM core to be coherent with > accesses made by other DMA peripherals, we must program a bus address > into those peripherals that causes the peripheral's accesses to use the > same set of caches that the ARM core's accesses will use. > > On the RPi1, the VideoCore firmware sets up the IOMMU to enable use of > the L2 cache. This corresponds to addresses based at 0x40000000. > > On the RPi2, the VideoCore firmware sets up the IOMMU to disable use of > the L2 cache. This corresponds to addresses based at 0xc0000000. > > This patch implements U-Boot's phys_to_bus/bus_to_phys APIs according > to those rules. > > For full details of this setup, please see Dom Cobley's description at: > http://lists.denx.de/pipermail/u-boot/2015-March/208201.html > http://permalink.gmane.org/gmane.comp.boot-loaders.u-boot/215038 > https://www.mail-archive.com/u-boot at lists.denx.de/msg166568.html > > Signed-off-by: Stephen Warren Applied to -next, thanks! Best regards, Marek Vasut