2015-05-13 18:37 GMT+02:00 Arnd Bergmann <arnd@xxxxxxxx>: > On Wednesday 13 May 2015 18:29:05 Maxime Coquelin wrote: >> 2015-05-13 17:28 GMT+02:00 Arnd Bergmann <arnd@xxxxxxxx>: >> > On Wednesday 13 May 2015 16:20:34 Daniel Thompson wrote: >> >> >> >> That would suit me very well (although is the 0x20/0x40 not the 8 that >> >> we would need in the middle column). >> > >> > We don't normally use register offsets in DT. The number 8 here instead >> > would indicate block 8, where each block is four bytes wide. Using the >> > same index here for reset and clock would also help readability. >> >> My view is that it makes the bindings usage very complex. >> Also, it implies we have a specific compatible for stm32f429, whereas >> we didn't need with my earlier proposals. >> Indeed, the reset driver will need to know the offset of every reset >> registers, because: >> 1. The AHB registers start at RCC offset 0x10 (up to 0x18) >> 2. The APB registers start at RCC offset 0x20 (up to 0x24). >> We have a gap between AHB and APB registers, so how do we map the >> index for the block you propose? >> Should the gap be considered as a block, or we should skip it? >> >> I'm afraid it will not be straightforward for a reset user to >> understand how to use this bindings. >> >> Either my v7 or v8 versions would have made possible to use a single >> compatible for STM32 series. >> If we stick with one of these, we could even think to have a "generic" >> reset driver, as it could be compatible with sunxi driver bindings. > > We should definitely try to use the same compatible string for all of > them, and make a binding that is easy to use. > > I haven't fully understood the requirements for the various parts that > are involved here. My understanding so far was that the driver could > use the index from the first cell and compute > > void __iomem *reset_reg = rcc_base + 0x10 + 4 * index; > void __iomem *clock_reg = rcc_base + 0x30 + 4 * index; This calculation is true, but we have to take into account there is a hole in the middle, between AHB3, and APB1 register: AHB1RSTR : offset = 0x10, index = 0 AHB2RSTR : offset = 0x14, index = 1 AHB3RSTR : offset = 0x18, index = 2 <HOLE > : offset = 0x1c, index = 3 APB1RSTR : offset = 0x20, index = 4 APB2RSTR : offset = 0x24, index = 5 So we have to carefully document this hole in the bindings, maybe by listing indexes in the documentation? > > Are there parts that need something else? If the 0x10 offset is > different, we probably want a different compatible string, and I'd > consider it a different part at that point. If there are chips > that do not spread the clock from the reset by exactly 256 bits, > we could add a DT property in the rcc node for that. I will check other chips, to see if this is valid generally. Thanks for your feedback, Maxime > > Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
