On 06/15/2015 02:10 AM, Antonio Borneo wrote:
On Sat, Jun 13, 2015 at 4:26 PM, Ellen Wang <ellen@xxxxxxxxxxxxxxxxxxx> wrote:
cp2112_i2c_xfer() only supports a single i2c_msg and only
reads up to 61 bytes. More than one message at a time
and longers reads just return errors. This breaks certain
important cases. For example, the at24 eeprom driver generates
paired write and read messages (for eeprom address and data).
And the reads can be larger than 61 bytes.
Since the device doesn't support i2c repeated starts in general,
but does support a single write-repeated-start-read pair
(as CP2112_DATA_WRITE_READ_REQUEST), we recognize the latter
case and implement only that.
To support large reads, we wrap a loop around cp2112_read()
to pick up all the returned data.
Hi Ellen,
to keep git log consistent, the subject should change to something like
HID: cp2112: ...
OK. Will fix.
Actually you are adding two features.
I think should be better to split them in two independent patches.
...
The part above goes in a patch for write-read, the part below in
another patch for large transfers.
I have tested you patch and works fine; I can read an I2C eeprom.
But I also check with an oscilloscope the I2C signals and I got
disappointed. There is no repeated START.
I can clearly see cp2112 generating a STOP immediately followed by a START.
Datasheet of cp2112 in figure 8 reports the expected time diagram with
repeated START, but it's not what I get on my HW.
Your code seam ok. Maybe my device is outdated or broken.
The errata document from Silabs does not report anythink relevant.
Can you verify with a scope on your HW too?
Thanks,
Antonio
...
Since the the long-read fix is less controversial, I've split it out and
sent it as a separate patch.
As for repeated start, it's not that easy for me to check it. The chip
is in a rack-mounted network switch. However, if you really want me to
verify it, I can pull the box out and hook it up on a bench.
The Silabs datasheet clearly states that the device is supposed to issue
a repeated start (rev 1.2,
http://www.silabs.com/Support%20Documents/TechnicalDocs/CP2112.pdf,
figure 8 on page 15).
Is your chip an older rev? Mine is rev 2 (but as you said, there would
have been an erratum if they fixed a hardware bug).
usb 1-1.2.3: New USB device found, idVendor=10c4, idProduct=ea90
usb 1-1.2.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1.2.3: Product: CP2112 HID USB-to-SMBus Bridge
usb 1-1.2.3: Manufacturer: Silicon Laboratories
usb 1-1.2.3: SerialNumber: 00343E9A
cp2112 0003:10C4:EA90.0001: hidraw0: USB HID v1.01 Device [Silicon
Laboratories
CP2112 HID USB-to-SMBus Bridge] on usb-0000:00:16.0-1.2.3/input0
cp2112 0003:10C4:EA90.0001: Part Number: 0x0C Device Version: 0x02
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