On Thu, Jun 13, 2013 at 07:25:20AM +0100, Pranavkumar Sawargaonkar wrote: > On 12 June 2013 18:58, Grant Likely <grant.lik...@secretlab.ca> wrote: > > On Mon, 3 Jun 2013 21:21:11 +0530, Pranavkumar Sawargaonkar > > <pranavku...@linaro.org> wrote: > >> One can just append earlyprintk=device-type,address (same as we pass > >> through command line) in "/chosen" node to notify kernel which is the > >> earlyprintk device and what is its address. > > > > I'm not a big fan of this. It seems to be short-circuiting around > > existing properties. The kernel /should/ be able to use the > > linux,stdout-path property to determine what the earlyprintk device > > to use is. > > For this there are two problems: > > 1. Early printk code gets initialized before un-flattening of a device tree. > Hence trying to find out node from stdout-path is tricky as we do not have > of_find_node_by_path available.
Looking at the existing uses of linux,stdout-path, it seems that it is pointed at an existing entry like &uart0, which cannot be parsed early enough. The base address is the main problem as it needs the DT to be unflattened (for example v2m_serial0 on arm64 would read as 0x90000 which is just an offset). If you pass the full path, of_find_node_by_path() wouldn't work either this early. Question for the DT guys - would it be feasible to pass a @<phys address> via the linux,stdout-path? Any other way to get the phys address of the device early during boot? > 2. Current compatible strings in arm64 early printk code are not in > synced (or different) from actual compatible strings used in drivers - > e.g. for PL011 In earlyprintk code match name is just pl011 but in dts > it is specified as "arm,pl011" Hence we will need multiple changes to > implement it. I think we can sort this out. The first point is more important. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
