Dear Stephen Warren, > On 11/02/2012 04:10 PM, Marek Vasut wrote: > > Dear Stephen Warren, > > > >> On 11/02/2012 03:28 PM, Marek Vasut wrote: > >>> Dear Stephen Warren, > >>> > >>>> On 11/02/2012 02:38 PM, Marek Vasut wrote: > >> ... > >> > >>>>> Dumb question -- might be unrelated. Does the tegra mmc driver do > >>>>> DMA? And if so, what happens if you do raw read to unaligned address > >>>>> (aka. how come you don't need the bounce buffer)? > >>>> > >>>> Yes, it does DMA, I believe. (At least if it doesn't, I have no idea > >>>> why the driver is flushing caches!) > >>>> > >>>> I guess we only support the use of aligned addresses, so e.g. the > >>>> following would work: > >>>> > >>>> ext2load mmc 0:1 0x00100000 /file > >>>> > >>>> but the following wouldn't: > >>>> > >>>> ext2load mmc 0:1 0x00100004 /file > >>>> > >>>> which while I suppose it is an artificial restriction, hasn't been an > >>>> issue in practice. > >>> > >>> Then just enable the bounce buffer and it will work ;-) > >> > >> You suggested that last time, and it made no difference then... In fact, > >> the config option you mentioned isn't used anywhere in the srouce tree > >> except adding bouncebuf.o > > > > Bouncebuf.o ? > > common/bouncebuf.c
Ugh, it was applied ... > >> into the build right now; which config option > >> do you think I should use? > > > > CONFIG_BOUNCE_BUFFER > > > > It's used on mx28-based boards. > > Ahah, there's much more to it than just defining the config option, and > grep'ing for the config option doesn't reveal that. > > Defining CONFIG_BOUNCE_BUFFER simply pulls in bouncebuf.o into the > build. It's then up to the individual MMC/... driver to actually make > use of the new functions - i.e. explicitly call e.g. > bounce_buffer_start(). The MXS MMC driver calls these without any ifdef > CONFIG_BOUNCE_BUFFER, and hence doesn't show up when you grep for that. > I had assumed that such functionality would be a conditional part of the > MMC core rather than the individual drivers, hence had missed the usage > in the MXS driver. Sorry about that, I didn't know the patch was pulled in so I expected the old approach. > So, that config option plus some changes to the Tegra MMC driver might > work - I'll take a look. However, making that change will simply hide > any unaligned buffer and reduce performance, so I'd still prefer to > require that buffers be aligned in the future where possible. Best regards, Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot