Hi, On Tue, Sep 18, 2012 at 2:21 PM, Marek Vasut <ma...@denx.de> wrote: > Dear Simon Glass, > >> Hi, >> >> On Tue, Sep 18, 2012 at 1:04 PM, Thierry Reding >> >> <thierry.red...@avionic-design.de> wrote: >> > On Tue, Sep 18, 2012 at 09:36:18PM +0200, Marek Vasut wrote: >> >> Dear Thierry Reding, >> >> >> >> [...] >> >> >> >> > > Sure, but after you apply the bounce buffer, you can safely >> >> > > invalidate the whole cacheline, so align it up and be done with it. >> >> > >> >> > That's what I proposed to do last time around but it was NAK'ed. >> >> >> >> By who? >> > >> > I think it was Simon Glass and Mike Frysinger. They NAK'ed it for very >> > valid reason, so I'm not complaining. >> > >> >> > At the >> >> > time I didn't ensure that the buffer was actually big enough, which is >> >> > why people didn't like it (data on the stack after the DMA buffer >> >> > might be invalidated as well). >> >> >> >> Correct, thus the bounce buffer. >> > >> > I don't think we even need the bounce buffer. All that needs to be done >> > is guarantee that the buffers passed to the MMC driver are properly >> > aligned and sized. >> > >> > Thierry >> >> Perhaps a point to make here is that we really don't want every driver >> (or even driver stack) implementing bounce buffers to when it is not a >> huge effort to change the code that calls them (typically filesystem >> code) to do the right thing. The code will be smaller and more >> efficient if the alignment issues are dealt with at source IMO. > > You need the BB for user-case, when user gives you misaligned buffer.
Yes, although I think you are talking about non-filesystem (i.e. raw) access, and it would be odd to read a kernel to a non-cached-aligned address. If we want to support that, we can (perhaps even in the command itself)., but at least U-Boot's own code should ideally not generate unaligned access. Regards, Simon > > Best regards, > Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
