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<TITLE>Example PPC-4xx DMA scatter/gather usage</TITLE>
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<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Does anyone have any example code they could provide me that shows correct usage of the Linux 2.6.x PPC-4xx scatter/</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">ga</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">ther DMA functionality?</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">None of the mainline kernel tree sources or module sources seem to use this functionality.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> </SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">I am working on a driver that runs</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> on an embedded PPC-405gp running linux 2.4.21</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">. The driver relies extensively on the PPC</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">’</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">s DMA controller</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">using</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">all 4 channels simultaneously.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"></FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial"></FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">After some research I determined that the version of the</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">dma</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> code that was in 2.4.21 had been significantly modified in more recent kernel trees. As a result I have merged in the 2.6.x version of this code, but am running into some trouble with sg transfers.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> Specifically, after setting up a</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">n</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> sgl</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> the way I used to with the 2.4.21 kernel, and then kicking off the transfer, nothing seems to get</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">transferred</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> When I attempt to remove sg elements from the sgl, the kernel complains saying that I</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">’</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">m trying to remove an element from an already empty sgl.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Any help, advice, or examples would be greatly appreciated. Thanks.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"></SPAN><A NAME=""><SPAN LANG="en-us"><FONT COLOR="#808080" SIZE=2 FACE="Arial">______________________</FONT></SPAN></A><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
<P ALIGN=LEFT><B><SPAN LANG="en-us"><FONT COLOR="#000080" SIZE=2 FACE="Arial">Greg Buhler</FONT></SPAN></B><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
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<P ALIGN=LEFT><SPAN LANG="en-us"><FONT COLOR="#000080" SIZE=2 FACE="Arial">greg.buhler@viasat.com</FONT></SPAN><SPAN LANG="en-us"></SPAN></P>
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