Hello,
first of all some background information to the hardware itself.
In my special case (the I2O driver see also drivers/message/i2o/* for
further information) the hardware uses a memory mapped I/O region of
around 128kb. This memory region contains 3 control ports which IMHO
don't make send to be cached.
The remaining memory is divided into 512 byte sized message frames. The
driver have to request one of the 512 byte message frames by reading on
one of the control ports, and gets back an address of the message frame
which he could use to write data into it. After finishing the address of
the message frame must be written back to the control register.
At the moment the driver writes each 32-bit word directly into the I/O
memory region.
My questions now are:
1) does the ioremap() have any advantage over ioremap_nocache() in this
case, because the memory is only written once, and not read by the driver
again?
2) does it make sense to prepare the message in kernel using a mempool,
and then copy over to the I/O memory at once using memcpy_toio instead of
writing each 32-bit word directly to the I/O memory?
3) at the moment MTRR is used for the messages (but not for the control
registers), does this have an advantage because each 32-bit word is
written separately? Or is it better to not use MTRR, and use the approach
described in 2)?
Any advice would be appreciated! Thank you very much in advance!
Best regards,
Markus Lidel
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Markus Lidel (Senior IT Consultant)
Shadow Connect GmbH
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D-86381 Krumbach
Germany
Phone: +49 82 82/99 51-0
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