Hi, On 16-03-01 21:07:09, Woody Wu wrote: > On Friday, February 26, 2016, <victorascroft@xxxxxxxxx> wrote: > > > Hi, > > > > On 16-02-26 00:55:40, Woody Wu wrote: > > > Hi, > > > > > > It seems, at least in 4.4.2 kernel, earlyprintk parameter supports > > > something like 's3c24xx,<addr>'. But I dont know where to find out the > > addr > > > value of the first uart port on my *s3c2416* based board. Can someone > > > please tell me? > > > > > > Also, I desire to know if the earlycon parameter supports the Samsung > > > S3C24xx uarts, if so, what should the value of the parameter look like? > > > > Have a look in the documentation here > > https://www.kernel.org/doc/Documentation/kernel-parameters.txt > > > > The kernels kernel-parameter.txt documentation file lists the supported > > drivers. > > > > Generally the UART0 port is used for debugging but I guess there is > > no such hard and fast rule. > > > > For your particular board, you can check which UART port is used > > as the debug serial console and then get the address for the concerned > > UART by checking the relevant dtsi file in > > arch/arm/boot/dts/s3c24xx.dtsi or perhaps one of the exynosX.dtsi files? > > > > UART0 port seems to have address of 0x50000000? > > > > Regards, > > Sanchayan. > > > Thanks for you pointing me to the dtsi files, very informational ! And, > yes, the uart0 address os 0x50000000 and I has made it work via > 'earlyprintk=serial,0x50000000,115200'. By the way, is this a physical > address or mmap-ed address? The addresses specified in the DTS files are always physical addresses. So 0x50000000 is a physical address. This address will be mapped using one of the ioremap calls by the driver and used further by kernel using readl/writel calls. You can see the earlycon support declaration here http://lxr.free-electrons.com/source/drivers/tty/serial/samsung.c#L2452 s3c24xx_serial_probe -->s3c24xx_serial_init_port ---->Call to devm_ioremap http://lxr.free-electrons.com/source/drivers/tty/serial/samsung.c#L1705 - Sanchayan. > > > > > > > > > Thank in advance, > > > > > > -woody > > > > > > > > > -- > > > Life is the only flaw in an otherwise perfect nonexistence > > > -- Schopenhauer > > > > > > woody > > > public key at http://subkeys.pgp.net:11371 (narkewoody@xxxxxxxxx > > <javascript:;>) > > > > > _______________________________________________ > > > Kernelnewbies mailing list > > > Kernelnewbies@xxxxxxxxxxxxxxxxx <javascript:;> > > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > > -- > Life is the only flaw in an otherwise perfect nonexistence > -- Schopenhauer > > woody > public key at http://subkeys.pgp.net:11371 (narkewoody@xxxxxxxxx) _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
