>-----Original Message-----
>From: David Brownell [mailto:[email protected]]
>Sent: 2008年12月24日 16:40
>To: Tang, Feng
>Cc: Linus Torvalds; [email protected]; Andrew Morton;
>Vernon Sauder
>Subject: Re: [spi-devel-general] [patch 2.6.28-rc9] spi: spi_write_then_read()
>regression fix
>
>On Tuesday 23 December 2008, Tang, Feng wrote:
>> o. After that it fails on 2.6.28, I wrote a new API inside
>> my driver which is similar to your 2.6.28 spi_write_then_read(),
>> but modify the buffer layout. And the new API works fine for my
>> max3111 device.
>
>Sounds to me like the issue is a buggy SPI controller
>driver ... is this a driver that's in mainline?
[Tang, Feng] The HW I use is a SPI controller from Synopsys, I wrote and am
still debugging the driver as the silicon is not stable yet.
>
>I've certainly seen a couple drivers that handled the
>full duplex behavior incorrectly, until they fixed that
>bug. As in, they wrote the tx_buf *then* read rx_buf
>(a half-duplex model) instead of doing them concurrently
>(the full-duplex model a spi_master must implement).
>
>
>> > Before: WWWWWW
>> > After: RRRRRR
>
>That's obviously incorrect, or you're introducing
>some new notation. See my previous notes.
I agree with your second assumption :). It's a new use case,
for the max3111 spi-uart device, no matter you write a valid char or a 0 to it,
the readback data may contain a valid data (some bits indicating the data is
valid or not), so no data should be dumped. Following link contains the
datasheet of max3111
http://pdf1.alldatasheet.com/datasheet-pdf/view/73121/MAXIM/MAX3110.html .
>
>- Dave
>
Thanks,
Feng
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