[PATCH 06/10] pnv/phb4: Set link-active status in HPSTAT and LMR registers

[Saif Abrar <saif.abrar@linux.vnet.ibm.com>]

Config-read the link-status register in the PCI-E macro,
Depending on the link-active bit, set the link-active status
in the HOTPLUG_STATUS and LINK_MANAGEMENT registers
Also, clear the Presence-status active low bit in HOTPLUG_STATUS reg
after config-reading the slot-status in the PCI-E macro.

Signed-off-by: Saif Abrar <saif.abrar@linux.vnet.ibm.com>
---
 hw/pci-host/pnv_phb4.c | 57 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 56 insertions(+), 1 deletion(-)

diff --git a/hw/pci-host/pnv_phb4.c b/hw/pci-host/pnv_phb4.c
index 4e3a6b37f9..7b3d75bae6 100644
--- a/hw/pci-host/pnv_phb4.c
+++ b/hw/pci-host/pnv_phb4.c
@@ -516,6 +516,19 @@ static uint32_t get_exp_offset(PnvPHB4 *phb)
     return rpc->exp_offset;
 }
 
+/*
+ * Config-read the link-status register in the PCI-E macro,
+ * convert to LE and check the link-active bit.
+ */
+static uint32_t is_link_active(PnvPHB4 *phb)
+{
+    uint32_t exp_offset = get_exp_offset(phb);
+
+    return (bswap32(pnv_phb4_rc_config_read(phb,
+                        exp_offset + PCI_EXP_LNKSTA, 4))
+            & PCI_EXP_LNKSTA_DLLLA);
+}
+
 #define RC_CONFIG_WRITE(a, v) pnv_phb4_rc_config_write(phb, a, 4, v)
 
 /*
@@ -757,6 +770,11 @@ static void pnv_phb4_reg_write(void *opaque, hwaddr off, uint64_t val,
         val = 0;
         break;
 
+    case PHB_PCIE_HOTPLUG_STATUS:
+        /* For normal operations, Simspeed diagnostic bit is always zero */
+        val &= PHB_PCIE_HPSTAT_SIMDIAG;
+        break;
+
     /* Read only registers */
     case PHB_CPU_LOADSTORE_STATUS:
     case PHB_ETU_ERR_SUMMARY:
@@ -968,8 +986,40 @@ static uint64_t pnv_phb4_reg_read(void *opaque, hwaddr off, unsigned size)
         val |= PHB_PCIE_DLP_INBAND_PRESENCE | PHB_PCIE_DLP_TL_LINKACT;
         return val;
 
+    /*
+     * Read PCI-E registers and set status for:
+     * - Card present (active low bit 10)
+     * - Link active  (bit 12)
+     */
     case PHB_PCIE_HOTPLUG_STATUS:
-        /* Clear write-only bit */
+        /*
+         * Presence-status bit hpi_present_n is active-low, with reset value 1.
+         * Start by setting this bit to 1, indicating the card is not present.
+         * Then check the PCI-E register and clear the bit if card is present.
+         */
+        val |= PHB_PCIE_HPSTAT_PRESENCE;
+
+        /* Get the PCI-E capability offset from the root-port */
+        uint32_t exp_base = get_exp_offset(phb);
+
+        /*
+         * Config-read the PCI-E macro register for slot-status.
+         * Method for config-read converts to BE value.
+         * To check actual bit in the PCI-E register,
+         * convert the value back to LE using bswap32().
+         * Clear the Presence-status active low bit.
+         */
+        if (bswap32(pnv_phb4_rc_config_read(phb, exp_base + PCI_EXP_SLTSTA, 4))
+                    & PCI_EXP_SLTSTA_PDS) {
+            val &= ~PHB_PCIE_HPSTAT_PRESENCE;
+        }
+
+        /* Check if link is active and set the bit */
+        if (is_link_active(phb)) {
+            val |= PHB_PCIE_HPSTAT_LINKACTIVE;
+        }
+
+        /* Clear write-only resample-bit */
         val &= ~PHB_PCIE_HPSTAT_RESAMPLE;
         return val;
 
@@ -977,6 +1027,11 @@ static uint64_t pnv_phb4_reg_read(void *opaque, hwaddr off, unsigned size)
     case PHB_PCIE_LMR:
         /* These write-only bits always read as 0 */
         val &= ~(PHB_PCIE_LMR_CHANGELW | PHB_PCIE_LMR_RETRAINLINK);
+
+        /* Check if link is active and set the bit */
+        if (is_link_active(phb)) {
+            val |= PHB_PCIE_LMR_LINKACTIVE;
+        }
         return val;
 
     /* Silent simple reads */
-- 
2.39.3