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<TITLE>kernel 2.6.15: cpm_uart driver broken?</TITLE>
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<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">For</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">David</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">Jander</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">an</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">d</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> Vitaly</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> Bordug</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">:</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Regarding DMA allocation for CPM uarts, we had a similar issue with our MPC857T and MPC8</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">8</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">5 boards.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> I think the real problem is that bus_to_virt</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">) and virt_to_bus() don</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">t work</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">o</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">n 8xx</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">platforms for addresses allocated using dma_alloc_coherent().</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">We had a</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> previous discussion</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">Pantelis Antoniou and he agreed that the use of bus_to_virt() and virt_to_bus() should be deprecated. This is also recommended in the whitepaper series that discussed porting device drivers</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">from 2.4 to</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">2.6.</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">What we did was</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">use dma_alloc_coherent() in cpm_uart_cpm1.c, saving dma_addr in the pinfo</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">structure</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"> The in cpm_uart_core</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">.c</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">we</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">use dma_addr as the base address for the cbd_bufaddr values in each of the</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">descriptors.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> The software, when accessing the DMA buffers, uses mem_addr as the base, applying the same offset computed previously for the dma addresses.</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> This technique is used in other drivers all over 2.6.</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">This avoids the configuration dependencies on the</FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> <FONT SIZE=2 FACE="Arial">conversion functions.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Ken Poole</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"></SPAN><A HREF="mailto:kpoole@bos.mrv.com"><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">kpoole@bos.mrv.com</FONT></U></SPAN><SPAN LANG="en-us"></SPAN></A><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"></SPAN></P>
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