On Thu, Jan 05, 2017 at 11:33:28PM +0000, André Przywara wrote: > On 05/01/17 17:57, Maxime Ripard wrote: > > Hi Rob, > > > > On Wed, Jan 04, 2017 at 08:07:50AM -0600, Rob Herring wrote: > >> On Mon, Jan 02, 2017 at 11:03:43PM +0000, Andre Przywara wrote: > >>> From: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> > >>> > >>> Unlike the A64 user manual reports, the third MMC controller on the > >>> A64 (and the only one capable of 8-bit HS400 eMMC transfers) has a > >>> DMA buffer size limit of 8KB (much like the very old Allwinner SoCs). > >>> This does not affect the other two controllers, so introduce a new > >>> DT compatible string to let the driver use different settings for that > >>> particular device. This will also help to enable the high-speed transfer > >>> modes of that controller later. > >>> > >>> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> > >>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx> > >>> --- > >>> Documentation/devicetree/bindings/mmc/sunxi-mmc.txt | 1 + > >>> drivers/mmc/host/sunxi-mmc.c | 7 +++++++ > >>> 2 files changed, 8 insertions(+) > >> > >> Acked-by: Rob Herring <robh@xxxxxxxxxx> > > > > Some kind of a digression on this: we have three MMC controllers on > > this SoC. Like this patch shows, the third one is clearly different, > > and supports both more modes, a wider bus, and specific quirks. We > > need a new compatible for this one, everything's perfect. > > > > However, the other two are mostly the same, but seems to need > > different tuning parameters to get more performances out of the > > controller (but this is unclear yet). How do we usually deal with > > that? > > I guess you wanted to hear Rob's opinion ;-), but "get more performance" > sounds like we add one (or more) properties to tune those values. > If I get this right, it works with default values, but is sub-optimal? That would be my understanding too, at least, it works in a decent way without fiddling with those parameters. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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