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authorIlya Katsnelson <me@0upti.me>2017-07-09 11:24:58 +0300
committerJohn Crispin <john@phrozen.org>2017-07-31 21:28:37 +0200
commitbb4d5006c0111bd49c0870f6d668ef295bf68681 (patch)
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parentd0fb048b0e978a6081e146a7360910a98f1baec6 (diff)
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ramips: fix PCI init on MT7620 with Linux 4.9+
So, this is kind of complicated. This has been upstream for a while, imported from OpenWRT/LEDE with some cleanups. LEDE ramips has stayed on linux-4.4 this whole time, with the old(er) version of the patch that had correct behavior[0], while upstream got changed[1]. When LEDE updated to kernel 4.9, the older version of the code from the patch got replaced with the upstream version containing the bug. The original behavior, however, seems to be correct here, as the official programming guide[2] indicates that bit 31 (PDRV_SW_SET) in register PPLL_CFG1 is reserved, but bit 23 (added as PPLL_LD) is the PPLL lock state (which also happens to line up with the error message). The original confusion probably comes from the double definition of PDRV_SW_SET[3, 4] in the upstream code, with one correct definition (31) and one incorrect one (23). I've also used the opportunity to clean up the error message a bit - it's still not really helpful to anyone who doesn't already know what the PPLL is, but at least it's slightly more readable now. This will probably need to be upstreamed as well, since with the way it's currently set up, it's unlikely PCI ever worked for anyone who's running an upstream kernel on that SoC. [0]: https://github.com/lede-project/source/blob/05d6e92594c507dcd1f4be6c1bcb2282fe1abe1f/target/linux/ramips/patches-4.4/0009-PCI-MIPS-adds-mt7620a-pcie-driver.patch#L259 [1]: https://github.com/torvalds/linux/blob/026d15f6b9878794fae1f794cae881ccd65052e5/arch/mips/pci/pci-mt7620.c#L246 [2]: http://www.anz.ru/files/mediatek/MT7620_ProgrammingGuide.pdf [3]: https://github.com/torvalds/linux/blob/026d15f6b9878794fae1f794cae881ccd65052e5/arch/mips/pci/pci-mt7620.c#L36 [4]: https://github.com/torvalds/linux/blob/026d15f6b9878794fae1f794cae881ccd65052e5/arch/mips/pci/pci-mt7620.c#L39 Signed-off-by: Ilya Katsnelson <me@0upti.me>
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