diff options
Diffstat (limited to 'hw/net/imx_fec.c')
| -rw-r--r-- | hw/net/imx_fec.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c index 9506f9b69f..6e297c5480 100644 --- a/hw/net/imx_fec.c +++ b/hw/net/imx_fec.c @@ -417,7 +417,33 @@ static void imx_enet_write_bd(IMXENETBufDesc *bd, dma_addr_t addr) static void imx_eth_update(IMXFECState *s) { - if (s->regs[ENET_EIR] & s->regs[ENET_EIMR] & ENET_INT_TS_TIMER) { + /* + * Previous versions of qemu had the ENET_INT_MAC and ENET_INT_TS_TIMER + * interrupts swapped. This worked with older versions of Linux (4.14 + * and older) since Linux associated both interrupt lines with Ethernet + * MAC interrupts. Specifically, + * - Linux 4.15 and later have separate interrupt handlers for the MAC and + * timer interrupts. Those versions of Linux fail with versions of QEMU + * with swapped interrupt assignments. + * - In linux 4.14, both interrupt lines were registered with the Ethernet + * MAC interrupt handler. As a result, all versions of qemu happen to + * work, though that is accidental. + * - In Linux 4.9 and older, the timer interrupt was registered directly + * with the Ethernet MAC interrupt handler. The MAC interrupt was + * redirected to a GPIO interrupt to work around erratum ERR006687. + * This was implemented using the SOC's IOMUX block. In qemu, this GPIO + * interrupt never fired since IOMUX is currently not supported in qemu. + * Linux instead received MAC interrupts on the timer interrupt. + * As a result, qemu versions with the swapped interrupt assignment work, + * albeit accidentally, but qemu versions with the correct interrupt + * assignment fail. + * + * To ensure that all versions of Linux work, generate ENET_INT_MAC + * interrrupts on both interrupt lines. This should be changed if and when + * qemu supports IOMUX. + */ + if (s->regs[ENET_EIR] & s->regs[ENET_EIMR] & + (ENET_INT_MAC | ENET_INT_TS_TIMER)) { qemu_set_irq(s->irq[1], 1); } else { qemu_set_irq(s->irq[1], 0); |