How to use earlycon and earlyprintk on Samsung S3C24xx
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? 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@gmail.com)
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.
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@gmail.com)
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On Friday, February 26, 2016, <victorascroft@gmail.com> 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?
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@gmail.com
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-- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer woody public key at http://subkeys.pgp.net:11371 (narkewoody@gmail.com)
Hi, On 16-03-01 21:07:09, Woody Wu wrote:
On Friday, February 26, 2016, <victorascroft@gmail.com> 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@gmail.com
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-- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer
woody public key at http://subkeys.pgp.net:11371 (narkewoody@gmail.com)
Tkanks a lot! On Wednesday, March 2, 2016, <victorascroft@gmail.com> wrote:
Hi,
On 16-03-01 21:07:09, Woody Wu wrote:
On Friday, February 26, 2016, <victorascroft@gmail.com <javascript:;>> 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@gmail.com
<javascript:;>
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_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org <javascript:;> <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@gmail.com <javascript:;>)
-- Life is the only flaw in an otherwise perfect nonexistence -- Schopenhauer woody public key at http://subkeys.pgp.net:11371 (narkewoody@gmail.com)
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Woody Wu