From: "Richard B. Johnson" <root@chaos.analogic.com>
To: Chris Friesen <cfriesen@nortelnetworks.com>
Cc: linux-kernel@vger.kernel.org, becker@scyld.com
Subject: Re: why this 1ms delay in mdio_read? (cont'd from "are ioctl calls supposed to take this long?")
Date: Fri, 6 Jul 2001 14:48:46 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.3.95.1010706143953.5031A-100000@chaos.analogic.com> (raw)
In-Reply-To: <3B4602BA.91C5DAD3@nortelnetworks.com>
On Fri, 6 Jul 2001, Chris Friesen wrote:
> The beginning of mdio_read() in tulip.c goes like this:
>
> static int mdio_read(struct device *dev, int phy_id, int location)
> {
> struct tulip_private *tp = (struct tulip_private *)dev->priv;
> int i;
> int read_cmd = (0xf6 << 10) | (phy_id << 5) | location;
> int retval = 0;
> long ioaddr = dev->base_addr;
> long mdio_addr = ioaddr + CSR9;
>
> if (tp->chip_id == LC82C168) {
> int i = 1000;
> outl(0x60020000 + (phy_id<<23) + (location<<18), ioaddr + 0xA0);
> inl(ioaddr + 0xA0);
> inl(ioaddr + 0xA0);
> while (--i > 0)
> if ( ! ((retval = inl(ioaddr + 0xA0)) & 0x80000000))
> return retval & 0xffff;
> return 0xffff;
> }
>
> if (tp->chip_id == COMET) {
> if (phy_id == 1) {
> if (location < 7)
> return inl(ioaddr + 0xB4 + (location<<2));
> else if (location == 17)
> return inl(ioaddr + 0xD0);
> else if (location >= 29 && location <= 31)
> return inl(ioaddr + 0xD4 + ((location-29)<<2));
> }
> return 0xffff;
> }
>
> mdelay(1); /* One ms delay... */
>
> ...rest of code...
>
What? What kernel version?
The code here says:
/* Establish sync by sending at least 32 logic ones */
for (i = 32; i >=0; i--) {..........}
There is a mdio_delay() between each of the bit operations. This
is required to give time for the chip's internals to set up.
There is no mdelay in any of the code in .../linux/drivers/net/tulip/.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
I was going to compile a list of innovations that could be
attributed to Microsoft. Once I realized that Ctrl-Alt-Del
was handled in the BIOS, I found that there aren't any.
next prev parent reply other threads:[~2001-07-06 18:49 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-07-06 13:34 are ioctl calls supposed to take this long? Chris Friesen
2001-07-06 14:41 ` Richard B. Johnson
2001-07-06 15:14 ` Chris Friesen
2001-07-06 15:32 ` Richard B. Johnson
2001-07-06 15:40 ` Chris Friesen
2001-07-06 18:26 ` why this 1ms delay in mdio_read? (cont'd from "are ioctl calls supposed to take this long?") Chris Friesen
2001-07-06 18:48 ` Richard B. Johnson [this message]
2001-07-06 19:35 ` Chris Friesen
2001-07-06 21:41 ` Donald Becker
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