pcilmr: Add support for unique hardware quirks

Make it possible to change receiver margining parameters depending on
current hardware specificity.

In our tests Intel Ice Lake CPUs RC ports reported
MaxVoltageOffset = 50 (RxA), which led to results several times bigger
than the results of the hardware debugger.
Looks like in Intel Sapphire Rapids this was fixed, these CPU RC ports
report MaxVoltageOffset = 12 (RxA). To solve the problem it was decided
to hardcode Volt Offset to 12 (120 mV) for Ice Lake RC ports.

In the case of margining a specific link, only information about
Downstream and Upstream ports should be sufficient to decide whether to
use quirks, so the feature was implemented based on a list of devices
(vendor - device - revision triples), whose problems are known.

Back to Ice Lake ports, according to Integrators List on the pci-sig site,
the list of possible RC ports of Ice Lake Xeon's includes at least three
more options (with ids 347B/C/D) besides the one used in this commit, but
we don't have such processors to check the relevance of the MaxVoltageOffset
problem for these ports.

Reviewed-by: Sergei Miroshnichenko <s.miroshnichenko@yadro.com>
Signed-off-by: Nikita Proshkin <n.proshkin@yadro.com>

4 files changed, 61 insertions, 1 deletions

diff --git a/lmr/lmr.h b/lmr/lmr.h
index d35b8ae..bb188fc 100644
--- a/lmr/lmr.h
+++ b/lmr/lmr.h
@@ -21,6 +21,8 @@
 #define MARGIN_TIM_RECOMMEND 30
 #define MARGIN_VOLT_MIN      50
 
+enum margin_hw { MARGIN_HW_DEFAULT, MARGIN_ICE_LAKE_RC };
+
 /* PCI Device wrapper for margining functions */
 struct margin_dev {
   struct pci_dev *dev;
@@ -29,6 +31,8 @@ struct margin_dev {
   u8 retimers_n;
   u8 link_speed;
 
+  enum margin_hw hw;
+
   /* Saved Device settings to restore after margining */
   u8 aspm;
   bool hasd; // Hardware Autonomous Speed Disable
@@ -209,6 +213,8 @@ void margin_log_receiver(struct margin_recv *recv);
 /* Margining in progress log */
 void margin_log_margining(struct margin_lanes_data arg);
 
+void margin_log_hw_quirks(struct margin_recv *recv);
+
 /* margin_results */
 
 void margin_results_print_brief(struct margin_results *results, u8 recvs_n);
diff --git a/lmr/margin.c b/lmr/margin.c
index 1f1fa2f..cc142fa 100644
--- a/lmr/margin.c
+++ b/lmr/margin.c
@@ -127,6 +127,20 @@ margin_report_cmd(struct margin_dev *dev, u8 lane, margin_cmd cmd, margin_cmd *r
          && margin_set_cmd(dev, lane, NO_COMMAND);
 }
 
+static void
+margin_apply_hw_quirks(struct margin_recv *recv)
+{
+  switch (recv->dev->hw)
+    {
+      case MARGIN_ICE_LAKE_RC:
+        if (recv->recvn == 1)
+          recv->params->volt_offset = 12;
+        break;
+      default:
+        break;
+    }
+}
+
 static bool
 read_params_internal(struct margin_dev *dev, u8 recvn, bool lane_reversal,
                      struct margin_params *params)
@@ -311,6 +325,8 @@ margin_test_receiver(struct margin_dev *dev, u8 recvn, struct margin_args *args,
 
   if (recv.parallel_lanes > params.max_lanes + 1)
     recv.parallel_lanes = params.max_lanes + 1;
+  margin_apply_hw_quirks(&recv);
+  margin_log_hw_quirks(&recv);
 
   results->tim_coef = (double)params.timing_offset / (double)params.timing_steps;
   results->volt_coef = (double)params.volt_offset / (double)params.volt_steps * 10.0;
diff --git a/lmr/margin_hw.c b/lmr/margin_hw.c
index c000132..fc427c8 100644
--- a/lmr/margin_hw.c
+++ b/lmr/margin_hw.c
@@ -10,6 +10,27 @@
 
 #include "lmr.h"
 
+static u16 special_hw[][4] =
+  // Vendor ID, Device ID, Revision ID, margin_hw
+  { { 0x8086, 0x347A, 0x4, MARGIN_ICE_LAKE_RC }, 
+    { 0xFFFF, 0, 0, MARGIN_HW_DEFAULT } 
+  };
+
+static enum margin_hw
+detect_unique_hw(struct pci_dev *dev)
+{
+  u16 vendor = pci_read_word(dev, PCI_VENDOR_ID);
+  u16 device = pci_read_word(dev, PCI_DEVICE_ID);
+  u8 revision = pci_read_byte(dev, PCI_REVISION_ID);
+
+  for (int i = 0; special_hw[i][0] != 0xFFFF; i++)
+    {
+      if (vendor == special_hw[i][0] && device == special_hw[i][1] && revision == special_hw[i][2])
+        return special_hw[i][3];
+    }
+  return MARGIN_HW_DEFAULT;
+}
+
 bool
 margin_verify_link(struct pci_dev *down_port, struct pci_dev *up_port)
 {
@@ -56,7 +77,8 @@ fill_dev_wrapper(struct pci_dev *dev)
         .retimers_n
         = (!!(pci_read_word(dev, cap->addr + PCI_EXP_LNKSTA2) & PCI_EXP_LINKSTA2_RETIMER))
           + (!!(pci_read_word(dev, cap->addr + PCI_EXP_LNKSTA2) & PCI_EXP_LINKSTA2_2RETIMERS)),
-        .link_speed = (pci_read_word(dev, cap->addr + PCI_EXP_LNKSTA) & PCI_EXP_LNKSTA_SPEED) };
+        .link_speed = (pci_read_word(dev, cap->addr + PCI_EXP_LNKSTA) & PCI_EXP_LNKSTA_SPEED),
+        .hw = detect_unique_hw(dev) };
   return res;
 }
 
diff --git a/lmr/margin_log.c b/lmr/margin_log.c
index 6833d1a..a93e07b 100644
--- a/lmr/margin_log.c
+++ b/lmr/margin_log.c
@@ -133,3 +133,19 @@ margin_log_margining(struct margin_lanes_data arg)
       fflush(stdout);
     }
 }
+
+void
+margin_log_hw_quirks(struct margin_recv *recv)
+{
+  switch (recv->dev->hw)
+    {
+      case MARGIN_ICE_LAKE_RC:
+        if (recv->recvn == 1)
+          margin_log("\nRx(A) is Intel Ice Lake RC port.\n"
+                     "Applying next quirks for margining process:\n"
+                     "  - Set MaxVoltageOffset to 12 (120 mV).\n");
+        break;
+      default:
+        break;
+    }
+}