[U-Boot] [PATCH v1 1/3] blackfin: Enable early print via the generic serial API.

[Sonic Zhang]

Hi Mike,

On Mon, May 13, 2013 at 12:42 PM, Mike Frysinger <vapier at gentoo.org> wrote:
> On Monday 13 May 2013 00:20:15 Sonic Zhang wrote:
>> Remove blackfin specific implementation of the generic serial API when
>> early print macro is defined.
>>
>> In BFIN_BOOT_BYPASS mode, don't call generic serial_puts, because
>> early print in bypass mode is running before code binary is relocated
>> to the link address.
>
> the link address of the function doesn't matter.  all Blackfin func calls are
> pcrel based, not absolute address calls.  i specifically crafted all of this
> early serial code so that this does work regardless of the address where the
> code happens to be executing.
>

When you developed the bfin serial driver, the generic serial API
serial_puts() is implemented in bfin serial driver directly. No such
link address issue.

void serial_putc(const char c)
 {
       uart_putc(UART_BASE, c);
 }

void serial_puts(const char *s)
 {
       while (*s)
               serial_putc(*s++);
 }

While in latest generic serial.c, serial_puts() calls uart_puts()
function in bfin serial via a pointer to the default serial_device
structure, which contains the link address in DRAM, other than a
relative jump.

void serial_puts(const char *s)
{
        get_current()->puts(s);
}

This has nothing to do with the patch " blackfin: Correct early serial
mess output in BYPASS boot mode.".

07f572c8 <_get_current>:
 7f572c8:       67 01           [--SP] = RETS;
 7f572ca:       58 a0           R0 = [P3 + 0x4];
 7f572cc:       a6 6f           SP += -0xc;             /* (-12) */
 7f572ce:       00 48           CC = !BITTST (R0, 0x0);         /* bit  0 */
 7f572d0:       08 18           IF CC JUMP 0x7f572e0 <_get_current+0x18>;
 7f572d2:       4a e1 f8 07     P2.H = 0x7f8;           /* (2040)
 P2=0x7f8e77c <_serial_devices> */
 7f572d6:       0a e1 80 e7     P2.L = 0xe780;          /* (-6272)
 P2=0x7f8e780 <_serial_current> */
 7f572da:       10 91           R0 = [P2];
 7f572dc:       00 0c           CC = R0 == 0x0;
 7f572de:       0b 14           IF !CC JUMP 0x7f572f4 <_get_current+0x2c> (BP);
> 7f572e0:       00 e3 02 02     CALL 0x7f576e4 <_default_serial_console>;
> 7f572e4:       00 0c           CC = R0 == 0x0;
 7f572e6:       07 14           IF !CC JUMP 0x7f572f4 <_get_current+0x2c> (BP);
 7f572e8:       40 e1 f7 07     R0.H = 0x7f7;           /* (2039)
 R0=0x7f7e764(133687140) */
 7f572ec:       00 e1 cc 03     R0.L = 0x3cc;           /* (972)
 R0=0x7f703cc(133628876) */
 7f572f0:       00 e3 8e 3e     CALL 0x7f5f00c <_panic>;
 7f572f4:       66 6c           SP += 0xc;              /* ( 12) */
 7f572f6:       27 01           RETS = [SP++];
 7f572f8:       10 00           RTS;
        ...

07f572fc <_serial_puts>:
 7f572fc:       78 05           [--SP] = (R7:7);
 7f572fe:       67 01           [--SP] = RETS;
 7f57300:       38 30           R7 = R0;
 7f57302:       a6 6f           SP += -0xc;             /* (-12) */
 7f57304:       ff e3 e2 ff     CALL 0x7f572c8 <_get_current>;
> 7f57308:       10 32           P2 = R0;
 7f5730a:       66 6c           SP += 0xc;              /* ( 12) */
 7f5730c:       27 01           RETS = [SP++];
 7f5730e:       07 30           R0 = R7;
 7f57310:       38 05           (R7:7) = [SP++];
 7f57312:       92 ae           P2 = [P2 + 0x28];
> 7f57314:       52 00           JUMP (P2);



Regards,

Sonic

> what doesn't work is if you try to use the early serial console with
> CONFIG_SYS_BFIN_UART (which allows all the serial devices to be selected on
> the fly).  but the header file specifically handles that:
> #ifndef CONFIG_DEBUG_EARLY_SERIAL
> # define CONFIG_SYS_BFIN_UART
> #endif
>
> i guess the problem is that this commit is wrong:
>
> commit 820edc18b5aefa8c82d420f6cba3e13b5631f9b8
> Author: Sonic Zhang <sonic.zhang at analog.com>
> Date:   Fri Nov 30 17:39:32 2012 +0800
>
>     blackfin: Correct early serial mess output in BYPASS boot mode.
>
> it shouldn't be messing with the addresses there
> -mike