Hi. When I was looking into the NAND controller/chips separation, this question popped up in my mind. Commit 2d472aba15ff169 provides us a more flexibility about the controller/chips connection. The connected NAND chips do not need to be homogeneous any more. My question is about the ->setup_data_interface() hook when switching between NAND chips with different speed (timing mode). Think about the case below: { compatible = "foo-nand-controller"; reg = <...>; #address-cells = <1>; #size-cells = <0>; nand@0 { reg = <0>; /* Slow NAND chip */ } nand@1 { reg = <1>; /* Fast NAND chip */ } } In this case, two devices /dev/mtdblock0 and /dev/mtdblock1 will appear. If a user gets access to those two devices in turns, I think ->setup_data_interface() should be invoked somehow in order to update the timing registers on the controller side. Currently, ->setup_data_interface() is invoked in nand_scan_tail() and that's it. So, both nand@0 and nand@1 are accessed by the timing mode of nand@1 (assuming nand@0 and nand@1 are initialized in this order) Of course, it depends on the controller. If a controller has a register set for every chip select, the hardware will be able to change the access speed automatically. I think most of controllers just have a single set of timing registers. So, when switching between different types of chips, the driver must update the timing registers. If this is a worthwhile usecase, should it be taken care of by the NAND framework, or by drivers ? I just thought we could do something in nand_get_device() / nand_release_device(). If this should be done per driver, drivers can update registers in select_target or select_chip. Thought? -- Best Regards Masahiro Yamada ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/