On Mon, Mar 09, 2015 at 09:40:13PM +0100, Hans de Goede wrote: > Hi All, > > This patch set has been a while in the making, so I'm very happy to present > the end result here, and I hope everyone likes it. > > Before talking about merging this there are 2 things which I would like to > point out: > > a) The musb controller in the sunxi SoCs uses some SRAM which needs to be > mapped to the musb controller by poking some bits in the SRAM controller, > just like the EMAC patches which were send a while back I've chosen to use > syscon for this, actually 2 of the patches in this set come directly from the > SRAM mapping patchset for the EMAC. > > I know that Maxime is not 100% in favor of using syscon: > http://lists.infradead.org/pipermail/linux-arm-kernel/2015-January/320221.html > > But I disagree with his arguments for writing a special driver for the SRAM > controller: And I disagree with your disagreement :) > 1) syscon was specifically designed for global system control registers like > this and is fine to use as long as there are no conflicts where 1 bit is of > interest to multiple drivers, and there is no such conflict here No. Syscon has been designed for being lazy. This is a huge abstraction non-sense. You have to put all the logic of dealing with some external register layout in clients drivers, including dealing with the different revisions/SoC that are different from that aspect, and duplicating that code across all client drivers. > 2) Maxime's other arguments seem to boil down to it would be nice / prettier > to have a specific driver for this, without really proving a hard need for > such a driver. But writing such a driver is going to be a lot of work, and > we've a ton of other work to do, and as said there is no real need for a > separate driver, syscon works fine for this. Actually, I already wrote some prototype for this. I'll clean this up and send it tonight/tomorrow. > 3) I actually believe that having a specific driver for this is a bad idea, > because that means inventing a whole new cross driver API for this, and > getting those right is, hard, a lot of work, and even then one is still likely > to get it wrong. We can avoid all this by going with the proven syscon solution. Except that modifying an in-kernel API, especially when we have two users, is easy. Moving back from syscon is not. > Maxime, can we please have your ack for moving forward with this using syscon? > (see above for my arguments why) If you can address my objections above, sure. Thanks for your awesome work on this, Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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