Robert Jarzmik <robert.jarzmik@xxxxxxx> writes: > Mark Rutland <mark.rutland@xxxxxxx> writes: > >> On Mon, Oct 03, 2016 at 06:11:23PM +0200, Robert Jarzmik wrote: >>> Mark Rutland <mark.rutland@xxxxxxx> writes: >>> >>> reg-u16-align4 tells that a specific hardware doesn't support 16 bit writes not >>> being 32 bits aligned, or said differently that a "store" 16 bits wide on an >>> address of the format 4*n + 2 deserves a special handling in the driver, while a >>> store 16 bits wide on an address of the format 4*n can follow the simple casual >>> case. >> >> If I've understood correctly, effectively the low 2 address lines to the >> device are hard-wired to zero, e.g. a 16-bit access to 4*n + 2 would go >> to 4*n + 0 on the device? Or is the failure case distinct from that? > It is distinct. > > The "awful truth" is that an FPGA lies between the system bus and the > smc91c111. And this FPGA cannot handle correctly the 4*n + 2 u16 writes. > >> Do we have other platforms where similar is true? e.g. u8 accesses >> requiring 16-bit alignment? > > Not really, ie. not with a alignement requirement. > > But there are of course these ones are handled by reg-io-width and the > SMC_USE_xxx_BITS flags as far as I understand it. These cases are when a > platform declares SMC91X_USE_16BIT or SMC91X_USE_32BIT, but not SMC91X_USE_8BIT, > which would make me think of : > - CONFIG_SH_SH4202_MICRODEV, > - CONFIG_M32R > - several omap1 boards > - 1 sa1100 board > - several MMP and realview boards > > With all these platforms, each u8 access is replaced with a u16 access and a > mask / shift + mask. Or so what should I call this entry if reg-u16-align4 is not a good candidate ? Cheers. -- Robert -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
