On 13 December 2011 15:11, Peter Maydell <peter.mayd...@linaro.org> wrote: > On 12 December 2011 06:43, Evgeny Voevodin <e.voevo...@samsung.com> wrote: >> From: Mitsyanko Igor <i.mitsya...@samsung.com> >> >> Data transfer direction between host controller and SD/MMC card is selected >> by >> host controller configuration registers, but whether we actually need or need >> not perform data transfer depends on type of last issued command. To avoid >> memorization of which type of command host controller issued the last time, >> we >> can use simple query procedures, to make sure that SD/MMC card is in the >> right state. The only query routine currently presented in SD/MMC card >> emulation is sd_data_ready(), this patch adds sd_receive_ready() routine. > > I've thought about this a bit more and spent some time poking through > the standards docs. I'm kind of suspicious of both this function and > the existing sd_data_ready(). Real hardware doesn't have these signals, > both ends of the sd-controller-to-card connection just do their thing > and trust that the other end is in the state it is supposed to be. > If you (in the controller model) don't already know whether you are > OK to send/receive data then you haven't modelled some part of the > controller's state properly.
Having thought even more :-), sd_data_ready() is actually modelling a real hardware behaviour: "have we seen the start bit on the data line?". So it is justifiable. I still don't think sd_receive_ready() is, though. -- PMM
