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MT-149497: net: fec: add imx8mm devinfo with UDP checksum quirk #42

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MT-149497: net: fec: add imx8mm devinfo with UDP checksum quirk #42

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76c4b6e
net: fec: add imx8mm devinfo with UDP checksum quirk
Overdr0ne Jun 3, 2026
06039cf
net: fec: clarify FEC_QUIRK_ERR_UDP_CSUM scope is IPv4-only
Overdr0ne Jun 17, 2026
ad22f5a
net: fec: fix unsafe skb header access in UDP checksum quirk
Overdr0ne Jun 17, 2026
a3cb016
net: fec: disable RACC PRODIS for imx8mm due to UDP checksum errata
Overdr0ne Jun 17, 2026
02f3ec8
net: fec: clear stale RACC option bits before applying PRODIS mask
Overdr0ne Jun 17, 2026
047e407
net: fec: document both workarounds driven by FEC_QUIRK_ERR_UDP_CSUM
Overdr0ne Jun 17, 2026
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10 changes: 10 additions & 0 deletions drivers/net/ethernet/freescale/fec.h
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Original file line number Diff line number Diff line change
Expand Up @@ -514,6 +514,16 @@ struct bufdesc_ex {
*/
#define FEC_QUIRK_HAS_MDIO_C45 BIT(24)

/* i.MX8MM FEC hardware RX checksum offload incorrectly validates certain IPv4
* UDP packets, causing them to be silently dropped. This quirk drives two
* workarounds:
* - fec_restart() clears FEC_RACC_PRODIS so the hardware stops discarding
* these frames before the driver receives them.
* - the RX path forces software re-validation for IPv4/UDP by downgrading
* CHECKSUM_UNNECESSARY to CHECKSUM_NONE.
*/
#define FEC_QUIRK_ERR_UDP_CSUM BIT(25)

struct bufdesc_prop {
int qid;
/* Address of Rx and Tx buffers */
Expand Down
50 changes: 46 additions & 4 deletions drivers/net/ethernet/freescale/fec_main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -154,6 +154,17 @@ static const struct fec_devinfo fec_imx6ul_info = {
FEC_QUIRK_HAS_MDIO_C45,
};

static const struct fec_devinfo fec_imx8mm_info = {
.quirks = FEC_QUIRK_ENET_MAC | FEC_QUIRK_HAS_GBIT |
FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM |
FEC_QUIRK_HAS_VLAN | FEC_QUIRK_HAS_AVB |
FEC_QUIRK_ERR007885 | FEC_QUIRK_BUG_CAPTURE |
FEC_QUIRK_HAS_RACC | FEC_QUIRK_HAS_COALESCE |
FEC_QUIRK_CLEAR_SETUP_MII | FEC_QUIRK_HAS_MULTI_QUEUES |
FEC_QUIRK_HAS_EEE | FEC_QUIRK_WAKEUP_FROM_INT2 |
FEC_QUIRK_HAS_MDIO_C45 | FEC_QUIRK_ERR_UDP_CSUM,
};

static const struct fec_devinfo fec_imx8mq_info = {
.quirks = FEC_QUIRK_ENET_MAC | FEC_QUIRK_HAS_GBIT |
FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM |
Expand Down Expand Up @@ -209,6 +220,9 @@ static struct platform_device_id fec_devtype[] = {
}, {
.name = "imx6ul-fec",
.driver_data = (kernel_ulong_t)&fec_imx6ul_info,
}, {
.name = "imx8mm-fec",
.driver_data = (kernel_ulong_t)&fec_imx8mm_info,
}, {
.name = "imx8mq-fec",
.driver_data = (kernel_ulong_t)&fec_imx8mq_info,
Expand All @@ -232,6 +246,7 @@ enum imx_fec_type {
MVF600_FEC,
IMX6SX_FEC,
IMX6UL_FEC,
IMX8MM_FEC,
IMX8MQ_FEC,
IMX8QM_FEC,
S32V234_FEC,
Expand All @@ -245,6 +260,7 @@ static const struct of_device_id fec_dt_ids[] = {
{ .compatible = "fsl,mvf600-fec", .data = &fec_devtype[MVF600_FEC], },
{ .compatible = "fsl,imx6sx-fec", .data = &fec_devtype[IMX6SX_FEC], },
{ .compatible = "fsl,imx6ul-fec", .data = &fec_devtype[IMX6UL_FEC], },
{ .compatible = "fsl,imx8mm-fec", .data = &fec_devtype[IMX8MM_FEC], },
{ .compatible = "fsl,imx8mq-fec", .data = &fec_devtype[IMX8MQ_FEC], },
{ .compatible = "fsl,imx8qm-fec", .data = &fec_devtype[IMX8QM_FEC], },
{ .compatible = "fsl,s32v234-fec", .data = &fec_devtype[S32V234_FEC], },
Expand Down Expand Up @@ -1093,11 +1109,25 @@ fec_restart(struct net_device *ndev)

/* align IP header */
val |= FEC_RACC_SHIFT16;
if (fep->csum_flags & FLAG_RX_CSUM_ENABLED)
if (fep->csum_flags & FLAG_RX_CSUM_ENABLED) {
/* set RX checksum */
val |= FEC_RACC_OPTIONS;
else
u32 racc_opts = FEC_RACC_OPTIONS;

/* i.MX8MM FEC incorrectly discards valid UDP frames when
* PRODIS is active due to a hardware checksum errata.
* Disable protocol discard for this variant only.
*/
if (fep->quirks & FEC_QUIRK_ERR_UDP_CSUM)
racc_opts &= ~FEC_RACC_PRODIS;
/* clear all option bits first so any masked-out bits
* (e.g. PRODIS) already set in the register are cleared
* rather than left active by the OR below
*/
val &= ~FEC_RACC_OPTIONS;
val |= racc_opts;
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} else {
val &= ~FEC_RACC_OPTIONS;
}
writel(val, fep->hwp + FEC_RACC);
writel(PKT_MAXBUF_SIZE, fep->hwp + FEC_FTRL);
}
Expand Down Expand Up @@ -1786,8 +1816,20 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
if (fep->bufdesc_ex &&
(fep->csum_flags & FLAG_RX_CSUM_ENABLED)) {
if (!(ebdp->cbd_esc & cpu_to_fec32(FLAG_RX_CSUM_ERROR))) {
/* don't check it */
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* i.MX8MM FEC HW checksum offload incorrectly
* validates certain UDP packets (FEC_QUIRK_ERR_UDP_CSUM).
* Force software re-validation for UDP only.
*/
if (fep->quirks & FEC_QUIRK_ERR_UDP_CSUM &&
skb->protocol == htons(ETH_P_IP)) {
struct iphdr _iph;
const struct iphdr *iph;

iph = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
if (iph && iph->protocol == IPPROTO_UDP)
skb->ip_summed = CHECKSUM_NONE;
}
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} else {
skb_checksum_none_assert(skb);
}
Expand Down