From: Heiko Schocher <hs@denx•de>
To: linuxppc-embedded@ozlabs•org
Subject: I2C bus issues on MPC8248
Date: Fri, 19 May 2006 18:37:26 +0200 [thread overview]
Message-ID: <1148056646.5943.20.camel@Zeus.EmbLux> (raw)
In-Reply-To:
Hello Laurent,
on Thu, 18 May 2006 14:33:58, Laurent Pinchart wrote:
> I'm trying to use the MPC8248 hardware I2C bus in a 2.6.16 kernel. The
> mailing
> list archives mention a driver for the MPC8260
> (http://ozlabs.org/pipermail/linuxppc-embedded/2006-May/022837.html) which I
> modified to reflect the memory map differences between the MPC8260 and the
> MPC8248, as mentionned in the e-mail.
>
> The good news is that the driver works. The bad news is that it doesn't work
OK.
> correctly.
:-(
> The Linux I2C layer probes the I2C bus for peripherals when drivers are
> loaded. The probing function writes a single byte with the device address and
> check if the data is acked. I monitored the SCL and SDA lines using an
[...]
> Using that code, no data is sent on the bus, the BD_SC_READY bit is never
> cleared and no interrupt is generated. Once again I suspected a CPM bug when
> writing a single byte on the bus, so I increased cbd_datlen to 2:
>
> tbdf[0].cbd_bufaddr = __pa(tb);
> tbdf[0].cbd_datlen = 2;
> tbdf[0].cbd_sc = count ? BD_SC_READY | BD_IIC_START :
> BD_SC_READY | BD_IIC_START | BD_SC_INTRPT |
> BD_SC_LAST | BD_SC_WRAP;
>
> This worked, and two bytes were written on the bus, leading me to believe that
> the CPM was at fault.
I don t know, if this is a CPM Bug, but it seems so to me ...
> Has anyone noticed the same behaviour ? Is there a workaround available ? I
> tried searching Freescale's website for CPM microcode updates but haven't
> found anything related to the I2C controller.
Yes, Holger Speck had the same problem. He solved it by doing the following:
If the cpm_iic_write is called with count = 0. He made a read with count = 1
I think this is safer than writing 2 Bytes to the Slave.
Could you try this?
Best regards
Heiko
next reply other threads:[~2006-05-19 16:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-19 16:37 Heiko Schocher [this message]
2006-05-22 9:06 ` I2C bus issues on MPC8248 Laurent Pinchart
-- strict thread matches above, loose matches on Subject: below --
2006-05-24 16:00 Belaire, Ron
2006-05-18 12:33 Laurent Pinchart
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