x86: Early-boot serial I/O support
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From: H. Peter Anvin on 10 Jul 2010 15:00 On 07/10/2010 11:07 AM, Pekka Enberg wrote: > This patch adds serial I/O support to very early boot printf(). It's useful for > debugging boot code when running Linux under KVM, for example. The actual code > was lifted from early printk. Yinghai is correct that this really needs to pick apart the command line, especially since there is already support for command-line parsing in the early boot code. I suggest we just reuse the earlyprintk= option, especially since it's basically the same code and so should have the same failure profile. > + > + while ((inb(early_serial_base + LSR)& XMTRDY) == 0&& --timeout) > + ; > + cpu_relax(); here, probably. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Cyrill Gorcunov on 10 Jul 2010 17:10 On Sat, Jul 10, 2010 at 10:40:20PM +0300, Pekka Enberg wrote: > This patch adds serial I/O support to very early boot printf(). It's useful for > debugging boot code when running Linux under KVM, for example. The actual code > was lifted from early printk. > > Cc: Cyrill Gorcunov <gorcunov(a)gmail.com> > Cc: Ingo Molnar <mingo(a)redhat.com> > Cc: Yinghai Lu <yinghai(a)kernel.org> > Signed-off-by: Pekka Enberg <penberg(a)cs.helsinki.fi> > --- > v1 -> v2: > > - Use 'earlyprintk' kernel parameter to determine whether to use > early serial or not as suggested by Yinghai and hpa. > > arch/x86/boot/boot.h | 16 +++++++ > arch/x86/boot/main.c | 3 + > arch/x86/boot/string.c | 41 ++++++++++++++++++ > arch/x86/boot/tty.c | 111 +++++++++++++++++++++++++++++++++++++++++++++--- > 4 files changed, 165 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h > index 98239d2..f05b5ac 100644 > --- a/arch/x86/boot/boot.h > +++ b/arch/x86/boot/boot.h > @@ -37,6 +37,8 @@ > extern struct setup_header hdr; > extern struct boot_params boot_params; > > +#define cpu_relax() asm volatile("rep; nop" ::: "memory") > + > /* Basic port I/O */ > static inline void outb(u8 v, u16 port) > { > @@ -203,6 +205,17 @@ static inline int isdigit(int ch) > return (ch >= '0') && (ch <= '9'); > } > > +static inline int isxdigit(int ch) > +{ > + if (isdigit(ch)) > + return true; > + > + if ((ch >= 'a') && (ch <= 'f')) > + return true; > + > + return (ch >= 'A') && (ch <= 'F'); > +} > + I suspect it's supposed to be static inline *bool*, right? -- Cyrill -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Pekka Enberg on 10 Jul 2010 17:20 H. Peter Anvin wrote: >> + >> + while ((inb(early_serial_base + LSR)& XMTRDY) == 0&& --timeout) >> + ; >> + > > cpu_relax(); here, probably. Fixed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: H. Peter Anvin on 10 Jul 2010 17:30 On 07/10/2010 02:17 PM, Pekka Enberg wrote: > Hi! > > On Sat, Jul 10, 2010 at 11:49 PM, Yinghai Lu <yinghai(a)kernel.org> wrote: >> can you analyze "console=uart8250,io,0x3f8,115200n8" instead? >> >> that is equal to "earlyprintk=ttyS0,115200 console=ttyS0,115200" >> >> so we only use one for all. >> >> also like to kill earlyprintk=ttyS0,115200 to favor earlycon > > hpa, what's your take on this? > > The 'console' variant seems overly complicated to me. We can add it > but we also need to check for 'earlyprintk' as long as it's supported > by the kernel. > earlyprintk= seems to be preferred over console= these days. Quite frankly it's idiotic to have the user enter as many low-level details as one has to do for the console= one. Now, as for the I/O base, the I/O base for legacy serial ports are available from a 4-element u16 array starting at absolute address 0x400. I don't think Linux currently examines that array -- instead relying on the hard-coded values 0x3f8, 0x2f8, 0x3e8, 0x2e8 -- but it might something to consider for the future. However, we should match the serial port subsystem there, of course. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Cyrill Gorcunov on 10 Jul 2010 17:40
On Sun, Jul 11, 2010 at 12:18:06AM +0300, Pekka Enberg wrote: > On Sun, Jul 11, 2010 at 12:07 AM, Cyrill Gorcunov <gorcunov(a)gmail.com> wrote: > >> @@ -203,6 +205,17 @@ static inline int isdigit(int ch) > >> � � � return (ch >= '0') && (ch <= '9'); > >> �} > >> > >> +static inline int isxdigit(int ch) > >> +{ > >> + � � if (isdigit(ch)) > >> + � � � � � � return true; > >> + > >> + � � if ((ch >= 'a') && (ch <= 'f')) > >> + � � � � � � return true; > >> + > >> + � � return (ch >= 'A') && (ch <= 'F'); > >> +} > >> + > > > > I suspect it's supposed to be static inline *bool*, right? > > Yes, but I followed 'isdigit' here for symmetry and it uses 'int'. > > Pekka > ok, I see -- Cyrill -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |