On Sun, 01 Mar 2015 17:23:11 -0500 , Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > Hi Kevin, > > On 11/24/2014 06:36 PM, Kevin Cernekee wrote: > > If an earlycon (stdout-path) node is being used, check for "big-endian" > > or "native-endian" properties and pass the appropriate iotype to the > > driver. > > > > Note that LE sets UPIO_MEM (8-bit) but BE sets UPIO_MEM32BE (32-bit). The > > big-endian property only really makes sense in the context of 32-bit > > registers, since 8-bit accesses never require data swapping. > > > > At some point, the of_earlycon code may want to pass in the reg-io-width, > > reg-offset, and reg-shift parameters too. > > > > Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxx> > > --- > > drivers/of/fdt.c | 7 ++++++- > > drivers/tty/serial/earlycon.c | 4 ++-- > > include/linux/serial_core.h | 2 +- > > 3 files changed, 9 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c > > index 658656f..9d21472 100644 > > --- a/drivers/of/fdt.c > > +++ b/drivers/of/fdt.c > > @@ -794,6 +794,8 @@ int __init early_init_dt_scan_chosen_serial(void) > > > > while (match->compatible[0]) { > > unsigned long addr; > > + unsigned char iotype = UPIO_MEM; > > + > > if (fdt_node_check_compatible(fdt, offset, match->compatible)) { > > match++; > > continue; > > @@ -803,7 +805,10 @@ int __init early_init_dt_scan_chosen_serial(void) > > if (!addr) > > return -ENXIO; > > > > - of_setup_earlycon(addr, match->data); > > + if (of_fdt_is_big_endian(fdt, offset)) > > + iotype = UPIO_MEM32BE; > > + > > + of_setup_earlycon(addr, iotype, match->data); > > I know these got ACKs already but as you point out in the commit log, > earlycon _will_ need reg-io-width, reg-offset and reg-shift. Since the > distinction between early_init_dt_scan_chosen_serial() and > of_setup_earlycon() is arbitrary, I'd rather see of_setup_earlycon() > taught to properly decode of_serial driver bindings instead of a > stack of parameters to of_setup_earlycon(). > > In fact, this patch allows a mis-defined devicetree to bring up a > functioning earlycon because the 'big-endian' property is directly > associated with UPIO_MEM32BE, which will create incompatibility problems > when DT earlycon is fixed to decode the of_serial DT bindings. That's a good point. This hasn't been merged yet, so there isn't any impact on addressing this. I would propose that for consistency, the earlycon code should always default to 8-bit access. if big-endian accesses are required, then reg-io-width + big-endian must be specified. Something like the following would do it and would be future-proof. We can add support for 16 or 64bit big or little endian access if it ever became necessary. static int of_flat_dt_get_iotype(unsigned long node) { int size, width = 1; __be32 *prop; bool bigendian = false; if (of_get_flat_dt_prop(node, "big-endian", NULL)); bigendian = true; prop = of_get_flat_dt_prop(node, "reg-io-width", &size); if (prop) { if (size != sizeof(u32)) return -EINVAL; width = fdt32_to_cpu(*prop); } switch (width) { case 1: return UPIO_MEM; /* big-endian flag has no effect */ case 4: return bigendian ? UPIO_MEM32BE : UPIO_MEM32; default: return -EINVAL; } } ... iotype = of_fdt_get_iotype(fdt, offset); if (iotype == UPIO_INVAL) /*fail*/ g. -- 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