On Mon, 2019-09-16 at 14:38 -0700, Palmer Dabbelt wrote: > On Mon, 16 Sep 2019 12:40:10 PDT (-0700), schwab@xxxxxxx wrote: > > On Sep 16 2019, Palmer Dabbelt <palmer@xxxxxxxxxx> wrote: > > > > > On Sun, 15 Sep 2019 23:42:53 PDT (-0700), Christoph Hellwig > > > wrote: > > > > On Fri, Sep 13, 2019 at 01:40:27PM -0700, Palmer Dabbelt wrote: > > > > > OpenEmbedded passes "earlycon=sbi", which I can find in the > > > > > doumentation. > > > > > I can't find anything about just "earlycon". I've sent a > > > > > patch adding sbi > > > > > to the list of earlycon arguments. > > > > > > > > earlycon without arguments is documented, although just for > > > > ARM64. > > > > I can send a patch to update it to properly cover all DT > > > > platforms > > > > in addition. > > > > > > Thanks. I've kind of lost track of the thread, but assuming that > > > does the > > > "automatically pick an earlycon" stuff then that's probably what > > > we should > > > be using in the distros. > > > > Except that it doesn't work. > > Sorry, once again I've lost track of the thread. > > The code looks generic. The device tree in arch/riscv for the HiFive > Unleashed > doesn't have a stdout-path set, which if I understand correctly is > used by the > automatic earlycon stuff to pick a console. I gave this a quick test > on QEMU, > which finds a 16550 earlycon for me. I use openembedded's > qemuriscv64 target, > the following diff to make sure I'm getting an earlycon > > diff --git a/drivers/tty/serial/8250/8250_early.c > b/drivers/tty/serial/8250/8250_early.c > index 5cd8c36c8fcc..61290714bbcb 100644 > --- a/drivers/tty/serial/8250/8250_early.c > +++ b/drivers/tty/serial/8250/8250_early.c > @@ -106,6 +106,7 @@ static void early_serial8250_write(struct console > *console, > struct earlycon_device *device = console->data; > struct uart_port *port = &device->port; > > + uart_console_write(port, "_e_", 3, serial_putc); > uart_console_write(port, s, count, serial_putc); > } > > and run this command line > > /home/palmer/work/linux/openembedded-riscv64/build/tmp- > glibc/work/x86_64-linux/qemu-helper-native/1.0-r1/recipe-sysroot- > native/usr/bin/qemu-system-riscv64 -device virtio-net- > device,netdev=net0,mac=52:54:00:12:35:02 -netdev > user,id=net0,hostfwd=tcp::2222-:22,hostfwd=tcp::2323- > :23,tftp=/home/palmer/work/linux/openembedded-riscv64/build/tmp- > glibc/deploy/images/qemuriscv64 -drive > id=disk0,file=/home/palmer/work/linux/openembedded-riscv64/build/tmp- > glibc/deploy/images/qemuriscv64/core-image-full-cmdline-qemuriscv64- > 20190711162644.rootfs.ext4,if=none,format=raw -device virtio-blk- > device,drive=disk0 -object rng-random,filename=/dev/urandom,id=rng0 > -device virtio-rng-device,rng=rng0 -show-cursor -monitor null -device > loader,file=/home/palmer/work/linux/linux/arch/riscv/boot/Image,addr= > 0x80200000 -nographic -machine virt -m 512 -serial mon:stdio > -serial null -kernel /home/palmer/work/linux/openembedded- > riscv64/build/tmp-glibc/deploy/images/qemuriscv64/fw_jump.elf -append > 'root=/dev/vda rw highres=off console=ttyS0 mem=512M ip=dhcp > earlycon ' > > which gives me some early stuff and then some non-early stuff > > _e_[ 0.407579] printk: console [ttyS0] disabled > _e_[ 0.409205] 10000000.uart: ttyS0 at MMIO 0x10000000 (irq = 10, > base_baud = 230400) is a 16550A > [ 0.410720] printk: console [ttyS0] enabled > _e_[ 0.410720] printk: console [ttyS0] enabled > [ 0.411391] printk: bootconsole [ns16550a0] disabled > _e_[ 0.411391] printk: bootconsole [ns16550a0] disabled > [ 0.420664] [drm] radeon kernel modesetting enabled. > [ 0.428086] random: fast init done > [ 0.429331] random: crng init done > [ 0.440678] loop: module loaded > [ 0.447607] virtio_blk virtio1: [vda] 262830 512-byte logical > blocks (135 MB/128 MiB) > [ 0.469483] libphy: Fixed MDIO Bus: probed > > If you don't have something like "/chosen/stdout-path = &uart0;" in > your device > tree, then that's probably the issue. Here's where it's set in > Christoph's > k210: > > > http://git.infradead.org/users/hch/riscv.git/blob/f10e64873eafc68516b8884c06b9290b9887633b:/arch/riscv/boot/dts/kendryte/kd210.dts#l20 > > but we don't set it for the HiFive Unleashed. I'd call that a bug, > something > like this > > diff --git a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts > b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts > index 93d68cbd64fe..6d0ec76d93fe 100644 > --- a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts > +++ b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts > @@ -13,6 +13,7 @@ > compatible = "sifive,hifive-unleashed-a00", "sifive,fu540- > c000"; > > chosen { > + stdout-path = &uart0; > }; > > cpus { > > should fix it. LMK if I've misunderstood something. > OpenSBI already adds this node to DT for U-Boot serial console. I have tested that just adding "earlycon" to the commandline works as long as you are using OpenSBI and SERIAL_EARLYCON is enabled. If this entry can be added to dt residing in kernel, we can remove the code that adds the "stdout-path" from OpenSBI. > _______________________________________________ > linux-riscv mailing list > linux-riscv@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-riscv -- Regards, Atish
