On Thu, 2020-11-12 at 11:06 +0100, Sascha Hauer wrote: > On Tue, Nov 10, 2020 at 10:43:30AM +0100, Ahmad Fatoum wrote: > > On 11/10/20 10:36 AM, Ahmad Fatoum wrote: > > > Hi, > > > > > > On 11/10/20 10:15 AM, Sascha Hauer wrote: > > > > On Tue, Nov 10, 2020 at 08:48:11AM +0100, Sascha Hauer wrote: > > > > > On Tue, Nov 10, 2020 at 07:33:53AM +0100, Rouven Czerwinski > > > > > wrote: > > > > > > On Mon, 2020-11-09 at 14:52 +0100, Lucas Stach wrote: > > > > > > > Am Montag, den 09.11.2020, 14:44 +0100 schrieb Rouven > > > > > > > Czerwinski: > > > > > > > > Annotate the different read and write functions with > > > > > > > > zero_page_{access/faulting}. This allows the cfi_flash > > > > > > > > driver to be used > > > > > > > > on the QEMU virt machine with an enabled MMU. > > > > > > > > > > > > > > I don't like this zero-page access allow in a driver at > > > > > > > all. If you > > > > > > > have some free address space somewhere, you could also > > > > > > > solve this issue > > > > > > > by remapping the IO resource to somewhere else in the > > > > > > > address space, > > > > > > > deviating from the 1:1 mapping. The Tegra PCIe host > > > > > > > driver does this, > > > > > > > if you need some inspiration. > > > > > > > > > > > > I totally agree, remapping the IO region sounds like a much > > > > > > better > > > > > > choice. > > > > > > > > > > But where should it be mapped to? Just 4k upwards and hope > > > > > that the area > > > > > just above the cfi flash isn't occupied by something else? > > > > > > > > Ok, here's the plan: > > > > > > > > In a board specific initcall map the memory to wherever it's > > > > convenient, > > > > modify the address of the CFI flash in the device node and add > > > > a big > > > > comment that there's nothing to see here. > > > > > > The device tree specification defines a "virtual-reg property > > > [that] specifies > > > an effective address that maps to the first physical address > > > specified in > > > the reg property of the device node. This property enables boot > > > programs to > > > provide client programs with virtual-to-physical mappings that > > > have been set up". > > > > > > So, how about a tad more generic approach: > > > > > > - barebox device tree extends cfi-flash node with virtual-reg of > > > appropriate > > > location > > > - Define a of_iomap() function that > > > > Or rather a more generic name, like dev_ioremap?.(In that case > > !CONFIG_OF is the same as MMU off). > > I wouldn't use ioremap as name when the function has a different > semantics, but other than that: Sounds good. Make it so! This only works if you have available IOMEM big enough somewhere, which is not the case on the qemu ARM virt platform. While I agree that having MMU enabled is great for testing, maybe we can just add !MMU as a dependency for the virt board. Regards, Rouven _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox