Pekon, On Fri, Oct 25, 2013 at 11:15:57AM +0000, Gupta, Pekon wrote: > Hi, > > > -----Original Message----- > > From: Ezequiel Garcia [mailto:ezequiel.garcia@xxxxxxxxxxxxxxxxxx] > [...] > > > Pekon, Brian: Do you think this solution might work for 8-bit and 16-bit > > devices? > > > I think NAND_BUSWIDTH_AUTO (without GPMC changes) would fail in > following scenarios.. > > Case-1: configuring gpmc,device-width=1 from DT when using x16 device. ... which is wrong. That's why we have a DT property to configure that. The GPMC *must* be properly configured. > As your NAND driver is using NAND_BUSWIDTH_AUTO, it should > ignore this DT config, and based on ONFI params it should work as x16 > Hm.. I don't think so. The auto-stuff is just for the NAND driver, not for the memory controller. I don't know much about hardware, but in my mind I imagine them as different controllers. > Case-2: configuring gpmc,device-width=2 from DT when using x8 device. ... which is also wrong. Once again, you're mis-configuring the GPMC. We cannot expect the NAND driver to work properly if the GPMC is not properly initialized, don't you think? > Actually having NAND_BUSWIDTH_AUTO would require change in GPMC > driver also.. please refer my comments in.. > http://lists.infradead.org/pipermail/linux-mtd/2013-October/049284.html > Well, I think the approach should be different and much simpler: GPMC *must* be properly configured and then NAND can do ONFI detection starting in 8-bit and then switching to 16-bit if needed. This is what this patch is doing: it _fixes_ the NAND driver ONFI detection, _provided_ the GPMC is well-prepared. You seem to think that GPMC + NAND should be able to automagically detect the device and work, but I don't think that's even physically possible, for the reasons you have just exposed. I think this fix is simple enough. BTW: The GPMC code ignores the DT value in 'gpmc,device-width' and uses 'nand-bus-width' instead, but that's a different bug and a different fix :) -- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
