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authorRizwan Qureshi <rizwan.qureshi@intel.com>2017-09-16 01:54:20 +0530
committerFurquan Shaikh <furquan@google.com>2017-09-21 03:14:49 +0000
commit03937391bc80613f4591b5f5c0d00d2607406dc2 (patch)
treec5f10fed7564b919859beee85404452799c4abdd /util/cbfstool/fmd_parser.h_shipped
parent1eb02592b3c3dd4970524db80e232f32bb0248e4 (diff)
soc/intel/skylake: Add config for enabling LTR for PCIe Root port
There are a lot errors reported by AER driver for root port 0. The erors are being caused by an unsupported request from the device to the upstream port. Enabling LTR on the root port stops these errors, it is because LTR is enabled on the device side but not on the root port and hence root port was logging the LTR messages from the device as unsupported. The PCIe base spec (v3.1a) section 6.18 also states that: LTR support is discovered and enabled through reporting and control registers described in Chapter 7. Software must not enable LTR in an Endpoint unless the Root Complex and all intermediate Switches indicate support for LTR. Note that it is not required that all Endpoints support LTR to permit enabling LTR in those Endpoints that do support it. When enabling the LTR mechanism in a hierarchy, devices closest to the Root Port must be enabled first. If an LTR Message is received at a Downstream Port that does not support LTR or if LTR is not enabled, the Message must be treated as an Unsupported Request. FSP has a UPD for enabling/disabling LTR on root port, use the same for configuring LTR on PCIe root ports. BUG=b:65570878 TEST=After enbaling LTR on port 0 on the MB devicetree, No errors reported by AER driver for root port 0. Change-Id: Ica97faa78fcd991dad63ae54d2ada82194b4202a Signed-off-by: Rizwan Qureshi <rizwan.qureshi@intel.com> Reviewed-on: https://review.coreboot.org/21547 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Furquan Shaikh <furquan@google.com> Reviewed-by: Aaron Durbin <adurbin@chromium.org>
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