[PATCH v2 11/19] hw/net/bcm2838_genet: implement GENET MDIO

[Marcelo Manzo <marcelomanzo@gmail.com>]

From: Sergey Kambalin <serg.oker@gmail.com>

Implement the MDIO command register handling used to read/write the
BCM54213PE PHY's standard MII registers (BMCR, BMSR, LPA, ...) plus
its vendor "shadow" register blocks reached through the AUX_CTL/
EXP_SHD indirection scheme, and a simple link-state model (PHY
starts down, comes up once BMCR is programmed and autonegotiation
is (re)started).

Part of Sergey Kambalin's original Raspberry Pi 4B PCIe/GENET
networking series (patchwork series 829638, posted to qemu-devel in
2024, never merged). Carried forward and completed by Marcelo Manzo;
see the following "Fix GENET PHY autonegotiation-restart deadlock"
patch for a real bug found and fixed in this code during testing.

Signed-off-by: Sergey Kambalin <sergey.kambalin@auriga.com>
Signed-off-by: Marcelo Manzo <marcelomanzo@gmail.com>
---
 hw/net/bcm2838_genet.c         | 132 ++++++++++++++++++++++++++++++++-
 include/hw/net/bcm2838_genet.h |   3 +-
 2 files changed, 132 insertions(+), 3 deletions(-)

diff --git a/hw/net/bcm2838_genet.c b/hw/net/bcm2838_genet.c
index f3c5ca26c5..6b3c9cb12b 100644
--- a/hw/net/bcm2838_genet.c
+++ b/hw/net/bcm2838_genet.c
@@ -216,6 +216,7 @@ FIELD(GENET_PHY_STAT_1000, LOCALRXOK, 13, 1)
 FIELD(GENET_PHY_STAT_1000, MSRES,     14, 1)
 FIELD(GENET_PHY_STAT_1000, MSFAIL,    15, 1)
 
+/* There are two data representations for PHY_AUX_CTRL register */
 REG16(GENET_PHY_AUX_CTRL_0,              0)
 FIELD(GENET_PHY_AUX_CTRL_0, REG_ID_MASK, 0, 3)
 FIELD(GENET_PHY_AUX_CTRL_0, RSVD_3,      3, 1)
@@ -272,6 +273,129 @@ static void bcm2838_genet_set_irq_prio(BCM2838GenetState *s)
     qemu_set_irq(s->irq_prio, level);
 }
 
+static void bcm2838_genet_phy_aux_ctl_write(BCM2838GenetState *s,
+                                            uint16_t value)
+{
+    uint16_t reg_id = FIELD_EX16(value, GENET_PHY_AUX_CTRL_0, REG_ID);
+    uint16_t reg_id_mask = FIELD_EX16(value, GENET_PHY_AUX_CTRL_0, REG_ID_MASK);
+    uint16_t misc_wren = FIELD_EX16(value, GENET_PHY_AUX_CTRL_0, MISC_WREN);
+    uint16_t reg_data = FIELD_EX16(value, GENET_PHY_AUX_CTRL_0, REG_DATA);
+    uint16_t reg_data12 = FIELD_EX16(value, GENET_PHY_AUX_CTRL_1, REG_DATA);
+
+    uint16_t *phy_aux_ctl_shd_reg_id =
+        (uint16_t *)&s->phy_aux_ctl_shd_regs + reg_id;
+    uint16_t *phy_aux_ctl_shd_reg_id_mask =
+        (uint16_t *)&s->phy_aux_ctl_shd_regs + reg_id_mask;
+
+    if (reg_id_mask == BCM2838_GENET_PHY_AUX_CTL_MISC) {
+        if (reg_id == BCM2838_GENET_PHY_AUX_CTL_MISC) {
+            if (misc_wren == 0) {
+                /* write for subsequent read (8-bit from AUX_CTL_MISC) */
+                FIELD_DP16(value, GENET_PHY_AUX_CTRL_0, REG_DATA,
+                          *phy_aux_ctl_shd_reg_id);
+            } else {
+                /* write 8 bits to AUX_CTL_MISC */
+                *phy_aux_ctl_shd_reg_id_mask = reg_data;
+            }
+        } else {
+            /* write for subsequent read (12-bit) */
+            FIELD_DP16(value, GENET_PHY_AUX_CTRL_1, REG_DATA,
+                      *phy_aux_ctl_shd_reg_id);
+        }
+    } else {
+        /* write 12 bits */
+        *phy_aux_ctl_shd_reg_id_mask = reg_data12;
+    }
+
+    s->phy_regs.aux_ctl = value;
+}
+
+static void bcm2838_genet_phy_shadow_write(BCM2838GenetState *s,
+                                           uint16_t value)
+{
+    uint16_t reg_id = FIELD_EX16(value, GENET_PHY_SHADOW, REG_ID);
+    uint16_t wr = FIELD_EX16(value, GENET_PHY_SHADOW, WR);
+    uint16_t reg_data = FIELD_EX16(value, GENET_PHY_SHADOW, REG_DATA);
+
+    uint16_t *phy_shd_reg = (uint16_t *)&s->phy_shd_regs + reg_id;
+
+    if (wr == 0) {
+        FIELD_DP16(value, GENET_PHY_SHADOW, REG_DATA, *phy_shd_reg);
+    } else {
+        *phy_shd_reg = reg_data;
+    }
+
+    s->phy_regs.shd = value;
+}
+
+static void bcm2838_genet_phy_exp_shadow_write(BCM2838GenetState *s,
+                                               uint16_t value)
+{
+    /*
+     * TODO Stub implementation without side effect,
+     * just storing registers values
+     */
+    uint16_t reg_id = FIELD_EX16(s->phy_regs.exp_ctrl,
+                                 GENET_PHY_EXP_SEL, REG_ID);
+    uint16_t block_id = FIELD_EX16(s->phy_regs.exp_ctrl,
+                                   GENET_PHY_EXP_SEL, BLOCK_ID);
+
+    s->phy_exp_shd_regs.regs[block_id][reg_id] = value;
+}
+
+static uint16_t bcm2838_genet_phy_exp_shadow_read(BCM2838GenetState *s)
+{
+    uint16_t reg_id = FIELD_EX16(s->phy_regs.exp_ctrl,
+                                 GENET_PHY_EXP_SEL, REG_ID);
+    uint16_t block_id = FIELD_EX16(s->phy_regs.exp_ctrl,
+                                   GENET_PHY_EXP_SEL, BLOCK_ID);
+
+    return s->phy_exp_shd_regs.regs[block_id][reg_id];
+}
+
+static uint64_t bcm2838_genet_mdio_cmd(BCM2838GenetState *s, uint64_t cmd)
+{
+    uint32_t phy_reg_id = FIELD_EX32(cmd, GENET_UMAC_MDIO_CMD, REG_ID);
+    uint32_t phy_reg_data = FIELD_EX32(cmd, GENET_UMAC_MDIO_CMD, REG_DATA);
+    uint32_t start_busy = FIELD_EX32(cmd, GENET_UMAC_MDIO_CMD, START_BUSY);
+    uint32_t rd = FIELD_EX32(cmd, GENET_UMAC_MDIO_CMD, RD);
+    uint32_t wr = FIELD_EX32(cmd, GENET_UMAC_MDIO_CMD, WR);
+    uint16_t *phy_reg = (uint16_t *)&s->phy_regs + phy_reg_id;
+
+    uint16_t anrestart = FIELD_EX16(phy_reg_data, GENET_PHY_BMCR, ANRESTART);
+
+    if (start_busy != 0) {
+        cmd = FIELD_DP32(cmd, GENET_UMAC_MDIO_CMD, START_BUSY, 0);
+
+        if (rd != 0) {
+            if (phy_reg_id == BCM2838_GENET_EXP_DATA) {
+                cmd = FIELD_DP32(cmd, GENET_UMAC_MDIO_CMD, REG_DATA,
+                                 bcm2838_genet_phy_exp_shadow_read(s));
+            } else {
+                cmd = FIELD_DP32(cmd, GENET_UMAC_MDIO_CMD, REG_DATA, *phy_reg);
+            }
+        } else if (wr != 0) {
+            if (phy_reg_id == BCM2838_GENET_PHY_AUX_CTL) {
+                bcm2838_genet_phy_aux_ctl_write(s, phy_reg_data);
+            } else if (phy_reg_id == BCM2838_GENET_PHY_SHD) {
+                bcm2838_genet_phy_shadow_write(s, phy_reg_data);
+            } else if (phy_reg_id == BCM2838_GENET_EXP_DATA) {
+                bcm2838_genet_phy_exp_shadow_write(s, phy_reg_data);
+            } else {
+                if (phy_reg_id == BCM2838_GENET_PHY_BMCR) {
+                    /* Initiate auto-negotiation once it has been restarted */
+                    if (anrestart == 1) {
+                        FIELD_DP16(phy_reg_data, GENET_PHY_BMCR, ANRESTART, 0);
+                    }
+                }
+                *phy_reg = phy_reg_data;
+            }
+        }
+    }
+
+    return cmd;
+}
+
 static uint64_t bcm2838_genet_read(void *opaque, hwaddr offset, unsigned size)
 {
     uint64_t value = ~0;
@@ -359,10 +483,13 @@ static void bcm2838_genet_write(void *opaque, hwaddr offset, uint64_t value,
             s->regs.rdma.status = (~value) & GENET_DMA_ENABLE_MASK;
             break;
         case BCM2838_GENET_UMAC_MDIO_CMD:
+            value = bcm2838_genet_mdio_cmd(s, value);
+            s->regs.intrl0.stat = FIELD_DP32(s->regs.intrl0.stat,
+                                             GENET_INTRL_0, MDIO_DONE, 1);
+            break;
         case BCM2838_GENET_TDMA_REGS
             ... BCM2838_GENET_TDMA_REGS + sizeof(BCM2838GenetRegsTdma) - 1:
-            qemu_log_mask(LOG_UNIMP,
-                "UMAC MDIO and TDMA aren't implemented yet");
+            qemu_log_mask(LOG_UNIMP, "TDMA isn't implemented yet");
             break;
         default:
             break;
@@ -464,6 +591,7 @@ static void bcm2838_genet_reset(Object *obj, ResetType type)
 
     trace_bcm2838_genet_reset("done");
 
+    bcm2838_genet_set_qemu_mac(s);
     bcm2838_genet_phy_reset(s);
 }
 
diff --git a/include/hw/net/bcm2838_genet.h b/include/hw/net/bcm2838_genet.h
index e3dee5a78f..b34c4b3ce7 100644
--- a/include/hw/net/bcm2838_genet.h
+++ b/include/hw/net/bcm2838_genet.h
@@ -103,7 +103,8 @@ OBJECT_DECLARE_SIMPLE_TYPE(BCM2838GenetState, BCM2838_GENET)
 #define BCM2838_GENET_EXP_DATA          BCM2838_GENET_PHY_REG(exp_data)
 #define BCM2838_GENET_EXP_SEL           BCM2838_GENET_PHY_REG(exp_ctrl)
 
-#define BCM2838_GENET_PHY_AUX_CTL_MISC  0x7
+#define BCM2838_GENET_PHY_AUX_CTL_AUXCTL    0x0
+#define BCM2838_GENET_PHY_AUX_CTL_MISC      0x7
 #define BCM2838_GENET_PHY_AUX_CTL_REGS_SIZE 8
 
 #define BCM2838_GENET_PHY_EXP_SHD_BLOCKS_CNT 256
-- 
2.47.1