Dear Timur,
In message <[EMAIL PROTECTED]> you wrote:
>
> How early? Is there anyone with an 8xx board that can test this out for me?
> I2C is used for programming DDR on 8xxx boards, and that's pretty early, but
> 8xxx doesn't have this problem.
For example, check the "LWMON" board (CONFIG_LWMON). This is a MPC823
based system, where the SCC2 port can be switched (yes, even at run
time) to be used either as a serial port or as Ethernet. If this
board is configured as serial console, this configuration must (1) be
detected by reading a register from an I2C attached PIC, and (2)
Ethernet must be switched off by writing a register in a I2C attached
PIC - see "cpu/mpc8xx/serial.c":
415 static int scc_init (void)
416 {
...
432 #if defined(CONFIG_LWMON) && defined(CONFIG_8xx_CONS_SCC2)
433 { /* Disable Ethernet, enable Serial */
434 uchar c;
435
436 c = pic_read (0x61);
437 c &= ~0x40; /* enable COM3 */
438 c |= 0x80; /* disable Ethernet */
439 pic_write (0x61, c);
pic_read() and pic_write() in turn call directly i2c_reg_read() resp.
i2c_reg_write().
I guess there are other places where things like this are used. Some
boards also come with a "console over modem" configuration which
might use I2C very early, IIRC.
> It seems "wrong" that i2c_reg_read() needs to initialize I2C, but i2c_read()
> doesn't.
You are certainly right. But when this code was added everthing was
much smaller and simpler ...
> I was going to CC: all the maintainers of 8xx boards, but they're too many of
> them.
He.
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: [EMAIL PROTECTED]
Some programming languages manage to absorb change, but withstand
progress. -- Epigrams in Programming, ACM SIGPLAN Sept. 1982
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