2013/3/18 Peter Maydell <peter.mayd...@linaro.org>: > On 18 March 2013 09:56, Kuo-Jung Su <dant...@gmail.com> wrote: >> The FTDDRII030 is responsible for SDRAM initialization. >> Which means the DDRII SDRAM would not be stabilized until the >> SDRAM is correctly initialized. >> => >> In QEMU, the memory_region_add_subregion() is used to perform this emulation. > > If you want to model "sdram doesn't work unless it's inited" > (which is optional, often for qemu it's fine to just have > the RAM always work), then the right way to do this is > probably to have this device provide a memory region which > is a container and which the SoC always maps. Then this device > just maps the RAM into the container when the guest does the > DDR init. Having the device mess with its parent's address > space is a red flag that you're not modelling things right. >
Got it, thanks. It sounds like a good idea to me, I'll try to model the ftddrii030 in that way. >> The FTAHBC030 is responsible for AHB device management (base + window size) >> and also the special case for AHB remap of slave4 and slave6. >> => >> In QEMU, >> 1. If SDRAM is initialized before activating AHB remap: >> memory_region_del_subregion() must be called prior to >> memory_region_add_subregion(). >> And this is the reason why I need '.ddr_inited' and >> '.ahb_remapped' in SoC struct. >> 2. If SDRAM is not yet initialized while activating AHB remap: >> Only memory_region_add_subregion() needs to be invoked. > > If you're handling add/del subregion then you need to model > this so that the device that does the add/del is working on > a memory region container that it controls. Then it can have > a private data structure field which tracks what the state > of the mapped subregions is. This almost always turns out to > be the same way the hardware design is structured. > > At the moment you have add/del going on in this device but > fields relating to what state the subregions are in are > at the top level soc state. > Got it, thanks > -- PMM -- Best wishes, Kuo-Jung Su
