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Commit 137f59d5 authored by Marc Kleine-Budde's avatar Marc Kleine-Budde
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can: at91_can: switch to rx-offload implementation 

The current at91_can driver uses NAPI to handle RX'ed CAN frames, the
RX IRQ is disabled and a NAPI poll is scheduled. Then in
at91_poll_rx() the RX'ed CAN frames are tried to read in order from
the device.

This approach has 2 drawbacks:

- Under high system load it might take too long from the initial RX
  IRQ to the NAPI poll function to run. This causes RX buffer
  overflows.
- The algorithm to read the CAN frames in order is not bullet proof
  and may fail under certain use cases/system loads.

The rx-offload helper fixes these problems by reading the RX'ed CAN
frames in the interrupt handler and adding it to a list sorted by RX
timestamp. This list of RX'ed SKBs is then passed to the networking
stack via NAPI.

Convert the RX path to rx-offload, pass all CAN error frames with
can_rx_offload_queue_timestamp().

Link: https://lore.kernel.org/all/20231005-at91_can-rx_offload-v2-27-9987d53600e0@pengutronix.deSigned-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent dd94a2f1
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Showing with 100 additions and 241 deletions
drivers/net/can/Kconfig
View file @ 137f59d5
......@@ -89,6 +89,7 @@ config CAN_RX_OFFLOAD
config CAN_AT91
tristate "Atmel AT91 onchip CAN controller"
depends on (ARCH_AT91 || COMPILE_TEST) && HAS_IOMEM
select CAN_RX_OFFLOAD
help
This is a driver for the SoC CAN controller in Atmel's AT91SAM9263
and AT91SAM9X5 processors.
......
drivers/net/can/at91_can.c
View file @ 137f59d5
......@@ -3,7 +3,7 @@
* at91_can.c - CAN network driver for AT91 SoC CAN controller
*
* (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
* (C) 2008, 2009, 2010, 2011 by Marc Kleine-Budde <kernel@pengutronix.de>
* (C) 2008, 2009, 2010, 2011, 2023 by Marc Kleine-Budde <kernel@pengutronix.de>
*/
#include <linux/bitfield.h>
......@@ -26,6 +26,7 @@
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/can/rx-offload.h>
#define AT91_MB_MASK(i) ((1 << (i)) - 1)
......@@ -142,7 +143,6 @@ enum at91_devtype {
struct at91_devtype_data {
unsigned int rx_first;
unsigned int rx_split;
unsigned int rx_last;
unsigned int tx_shift;
enum at91_devtype type;
......@@ -150,14 +150,13 @@ struct at91_devtype_data {
struct at91_priv {
struct can_priv can; /* must be the first member! */
struct napi_struct napi;
struct can_rx_offload offload;
struct phy *transceiver;
void __iomem *reg_base;
unsigned int tx_head;
unsigned int tx_tail;
unsigned int rx_next;
struct at91_devtype_data devtype_data;
struct clk *clk;
......@@ -166,9 +165,13 @@ struct at91_priv {
canid_t mb0_id;
};
static inline struct at91_priv *rx_offload_to_priv(struct can_rx_offload *offload)
{
return container_of(offload, struct at91_priv, offload);
}
static const struct at91_devtype_data at91_at91sam9263_data = {
.rx_first = 1,
.rx_split = 8,
.rx_last = 11,
.tx_shift = 2,
.type = AT91_DEVTYPE_SAM9263,
......@@ -176,7 +179,6 @@ static const struct at91_devtype_data at91_at91sam9263_data = {
static const struct at91_devtype_data at91_at91sam9x5_data = {
.rx_first = 0,
.rx_split = 4,
.rx_last = 5,
.tx_shift = 1,
.type = AT91_DEVTYPE_SAM9X5,
......@@ -213,27 +215,6 @@ static inline unsigned int get_mb_rx_last(const struct at91_priv *priv)
return priv->devtype_data.rx_last;
}
static inline unsigned int get_mb_rx_split(const struct at91_priv *priv)
{
return priv->devtype_data.rx_split;
}
static inline unsigned int get_mb_rx_num(const struct at91_priv *priv)
{
return get_mb_rx_last(priv) - get_mb_rx_first(priv) + 1;
}
static inline unsigned int get_mb_rx_low_last(const struct at91_priv *priv)
{
return get_mb_rx_split(priv) - 1;
}
static inline unsigned int get_mb_rx_low_mask(const struct at91_priv *priv)
{
return AT91_MB_MASK(get_mb_rx_split(priv)) &
~AT91_MB_MASK(get_mb_rx_first(priv));
}
static inline unsigned int get_mb_tx_shift(const struct at91_priv *priv)
{
return priv->devtype_data.tx_shift;
......@@ -374,9 +355,8 @@ static void at91_setup_mailboxes(struct net_device *dev)
for (i = get_mb_tx_first(priv); i <= get_mb_tx_last(priv); i++)
set_mb_mode_prio(priv, i, AT91_MB_MODE_TX, 0);
/* Reset tx and rx helper pointers */
/* Reset tx helper pointers */
priv->tx_head = priv->tx_tail = 0;
priv->rx_next = get_mb_rx_first(priv);
}
static int at91_set_bittiming(struct net_device *dev)
......@@ -548,34 +528,6 @@ static netdev_tx_t at91_start_xmit(struct sk_buff *skb, struct net_device *dev)
return NETDEV_TX_OK;
}
/**
* at91_activate_rx_low - activate lower rx mailboxes
* @priv: a91 context
*
* Reenables the lower mailboxes for reception of new CAN messages
*/
static inline void at91_activate_rx_low(const struct at91_priv *priv)
{
u32 mask = get_mb_rx_low_mask(priv);
at91_write(priv, AT91_TCR, mask);
}
/**
* at91_activate_rx_mb - reactive single rx mailbox
* @priv: a91 context
* @mb: mailbox to reactivate
*
* Reenables given mailbox for reception of new CAN messages
*/
static inline void at91_activate_rx_mb(const struct at91_priv *priv,
unsigned int mb)
{
u32 mask = 1 << mb;
at91_write(priv, AT91_TCR, mask);
}
static inline u32 at91_get_timestamp(const struct at91_priv *priv)
{
return at91_read(priv, AT91_TIM);
......@@ -600,37 +552,60 @@ static void at91_rx_overflow_err(struct net_device *dev)
{
struct net_device_stats *stats = &dev->stats;
struct sk_buff *skb;
struct at91_priv *priv = netdev_priv(dev);
struct can_frame *cf;
u32 timestamp;
int err;
netdev_dbg(dev, "RX buffer overflow\n");
stats->rx_over_errors++;
stats->rx_errors++;
skb = alloc_can_err_skb(dev, &cf);
skb = at91_alloc_can_err_skb(dev, &cf, &timestamp);
if (unlikely(!skb))
return;
cf->can_id |= CAN_ERR_CRTL;
cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
netif_receive_skb(skb);
err = can_rx_offload_queue_timestamp(&priv->offload, skb, timestamp);
if (err)
stats->rx_fifo_errors++;
}
/**
* at91_read_mb - read CAN msg from mailbox (lowlevel impl)
* @dev: net device
* at91_mailbox_read - read CAN msg from mailbox
* @offload: rx-offload
* @mb: mailbox number to read from
* @cf: can frame where to store message
* @timestamp: pointer to 32 bit timestamp
* @drop: true indicated mailbox to mark as read and drop frame
*
* Reads a CAN message from the given mailbox and stores data into
* given can frame. "mb" and "cf" must be valid.
* Reads a CAN message from the given mailbox if not empty.
*/
static void at91_read_mb(struct net_device *dev, unsigned int mb,
struct can_frame *cf)
static struct sk_buff *at91_mailbox_read(struct can_rx_offload *offload,
unsigned int mb, u32 *timestamp,
bool drop)
{
const struct at91_priv *priv = netdev_priv(dev);
const struct at91_priv *priv = rx_offload_to_priv(offload);
struct can_frame *cf;
struct sk_buff *skb;
u32 reg_msr, reg_mid;
reg_msr = at91_read(priv, AT91_MSR(mb));
if (!(reg_msr & AT91_MSR_MRDY))
return NULL;
if (unlikely(drop)) {
skb = ERR_PTR(-ENOBUFS);
goto mark_as_read;
}
skb = alloc_can_skb(offload->dev, &cf);
if (unlikely(!skb)) {
skb = ERR_PTR(-ENOMEM);
goto mark_as_read;
}
reg_mid = at91_read(priv, AT91_MID(mb));
if (reg_mid & AT91_MID_MIDE)
cf->can_id = FIELD_GET(AT91_MID_MIDVA_MASK | AT91_MID_MIDVB_MASK, reg_mid) |
......@@ -638,7 +613,9 @@ static void at91_read_mb(struct net_device *dev, unsigned int mb,
else
cf->can_id = FIELD_GET(AT91_MID_MIDVA_MASK, reg_mid);
reg_msr = at91_read(priv, AT91_MSR(mb));
/* extend timestamp to full 32 bit */
*timestamp = FIELD_GET(AT91_MSR_MTIMESTAMP_MASK, reg_msr) << 16;
cf->len = can_cc_dlc2len(FIELD_GET(AT91_MSR_MDLC_MASK, reg_msr));
if (reg_msr & AT91_MSR_MRTR) {
......@@ -652,151 +629,12 @@ static void at91_read_mb(struct net_device *dev, unsigned int mb,
at91_write(priv, AT91_MID(mb), AT91_MID_MIDE);
if (unlikely(mb == get_mb_rx_last(priv) && reg_msr & AT91_MSR_MMI))
at91_rx_overflow_err(dev);
}
at91_rx_overflow_err(offload->dev);
/**
* at91_read_msg - read CAN message from mailbox
* @dev: net device
* @mb: mail box to read from
*
* Reads a CAN message from given mailbox, and put into linux network
* RX queue, does all housekeeping chores (stats, ...)
*/
static void at91_read_msg(struct net_device *dev, unsigned int mb)
{
struct net_device_stats *stats = &dev->stats;
struct can_frame *cf;
struct sk_buff *skb;
skb = alloc_can_skb(dev, &cf);
if (unlikely(!skb)) {
stats->rx_dropped++;
return;
}
mark_as_read:
at91_write(priv, AT91_MCR(mb), AT91_MCR_MTCR);
at91_read_mb(dev, mb, cf);
stats->rx_packets++;
if (!(cf->can_id & CAN_RTR_FLAG))
stats->rx_bytes += cf->len;
netif_receive_skb(skb);
}
/**
* at91_poll_rx - read multiple CAN messages from mailboxes
* @dev: net device
* @quota: max number of pkgs we're allowed to receive
*
* Theory of Operation:
*
* About 3/4 of the mailboxes (get_mb_rx_first()...get_mb_rx_last())
* on the chip are reserved for RX. We split them into 2 groups. The
* lower group ranges from get_mb_rx_first() to get_mb_rx_low_last().
*
* Like it or not, but the chip always saves a received CAN message
* into the first free mailbox it finds (starting with the
* lowest). This makes it very difficult to read the messages in the
* right order from the chip. This is how we work around that problem:
*
* The first message goes into mb nr. 1 and issues an interrupt. All
* rx ints are disabled in the interrupt handler and a napi poll is
* scheduled. We read the mailbox, but do _not_ re-enable the mb (to
* receive another message).
*
* lower mbxs upper
* ____^______ __^__
* / \ / \
* +-+-+-+-+-+-+-+-++-+-+-+-+
* | |x|x|x|x|x|x|x|| | | | |
* +-+-+-+-+-+-+-+-++-+-+-+-+
* 0 0 0 0 0 0 0 0 0 0 1 1 \ mail
* 0 1 2 3 4 5 6 7 8 9 0 1 / box
* ^
* |
* \
* unused, due to chip bug
*
* The variable priv->rx_next points to the next mailbox to read a
* message from. As long we're in the lower mailboxes we just read the
* mailbox but not re-enable it.
*
* With completion of the last of the lower mailboxes, we re-enable the
* whole first group, but continue to look for filled mailboxes in the
* upper mailboxes. Imagine the second group like overflow mailboxes,
* which takes CAN messages if the lower goup is full. While in the
* upper group we re-enable the mailbox right after reading it. Giving
* the chip more room to store messages.
*
* After finishing we look again in the lower group if we've still
* quota.
*
*/
static int at91_poll_rx(struct net_device *dev, int quota)
{
struct at91_priv *priv = netdev_priv(dev);
u32 reg_sr = at91_read(priv, AT91_SR);
const unsigned long *addr = (unsigned long *)&reg_sr;
unsigned int mb;
int received = 0;
if (priv->rx_next > get_mb_rx_low_last(priv) &&
reg_sr & get_mb_rx_low_mask(priv))
netdev_info(dev,
"order of incoming frames cannot be guaranteed\n");
again:
for (mb = find_next_bit(addr, get_mb_tx_first(priv), priv->rx_next);
mb < get_mb_tx_first(priv) && quota > 0;
reg_sr = at91_read(priv, AT91_SR),
mb = find_next_bit(addr, get_mb_tx_first(priv), ++priv->rx_next)) {
at91_read_msg(dev, mb);
/* reactivate mailboxes */
if (mb == get_mb_rx_low_last(priv))
/* all lower mailboxed, if just finished it */
at91_activate_rx_low(priv);
else if (mb > get_mb_rx_low_last(priv))
/* only the mailbox we read */
at91_activate_rx_mb(priv, mb);
received++;
quota--;
}
/* upper group completed, look again in lower */
if (priv->rx_next > get_mb_rx_low_last(priv) &&
mb > get_mb_rx_last(priv)) {
priv->rx_next = get_mb_rx_first(priv);
if (quota > 0)
goto again;
}
return received;
}
static int at91_poll(struct napi_struct *napi, int quota)
{
struct net_device *dev = napi->dev;
const struct at91_priv *priv = netdev_priv(dev);
u32 reg_sr = at91_read(priv, AT91_SR);
int work_done = 0;
if (reg_sr & get_irq_mb_rx(priv))
work_done += at91_poll_rx(dev, quota - work_done);
if (work_done < quota) {
/* enable IRQs for frame errors and all mailboxes >= rx_next */
u32 reg_ier = AT91_IRQ_ERR_FRAME;
reg_ier |= get_irq_mb_rx(priv) & ~AT91_MB_MASK(priv->rx_next);
napi_complete_done(napi, work_done);
at91_write(priv, AT91_IER, reg_ier);
}
return work_done;
return skb;
}
/* theory of operation:
......@@ -816,8 +654,6 @@ static void at91_irq_tx(struct net_device *dev, u32 reg_sr)
u32 reg_msr;
unsigned int mb;
/* masking of reg_sr not needed, already done by at91_irq */
for (/* nix */; (priv->tx_head - priv->tx_tail) > 0; priv->tx_tail++) {
mb = get_tx_tail_mb(priv);
......@@ -855,11 +691,14 @@ static void at91_irq_tx(struct net_device *dev, u32 reg_sr)
static void at91_irq_err_line(struct net_device *dev, const u32 reg_sr)
{
struct net_device_stats *stats = &dev->stats;
enum can_state new_state, rx_state, tx_state;
struct at91_priv *priv = netdev_priv(dev);
struct can_berr_counter bec;
struct sk_buff *skb;
struct can_frame *cf;
u32 timestamp;
int err;
at91_get_berr_counter(dev, &bec);
can_state_get_by_berr_counter(dev, &bec, &tx_state, &rx_state);
......@@ -889,7 +728,7 @@ static void at91_irq_err_line(struct net_device *dev, const u32 reg_sr)
/* The skb allocation might fail, but can_change_state()
* handles cf == NULL.
*/
skb = alloc_can_err_skb(dev, &cf);
skb = at91_alloc_can_err_skb(dev, &cf, &timestamp);
can_change_state(dev, cf, tx_state, rx_state);
if (new_state == CAN_STATE_BUS_OFF) {
......@@ -906,19 +745,23 @@ static void at91_irq_err_line(struct net_device *dev, const u32 reg_sr)
cf->data[7] = bec.rxerr;
}
netif_rx(skb);
err = can_rx_offload_queue_timestamp(&priv->offload, skb, timestamp);
if (err)
stats->rx_fifo_errors++;
}
static void at91_irq_err_frame(struct net_device *dev, const u32 reg_sr)
{
struct net_device_stats *stats = &dev->stats;
struct at91_priv *priv = netdev_priv(dev);
struct can_frame *cf;
struct sk_buff *skb;
struct can_frame *cf = NULL;
u32 timestamp;
int err;
priv->can.can_stats.bus_error++;
skb = alloc_can_err_skb(dev, &cf);
skb = at91_alloc_can_err_skb(dev, &cf, &timestamp);
if (cf)
cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
......@@ -967,50 +810,62 @@ static void at91_irq_err_frame(struct net_device *dev, const u32 reg_sr)
if (!cf)
return;
netif_receive_skb(skb);
err = can_rx_offload_queue_timestamp(&priv->offload, skb, timestamp);
if (err)
stats->rx_fifo_errors++;
}
static u32 at91_get_reg_sr_rx(const struct at91_priv *priv, u32 *reg_sr_p)
{
const u32 reg_sr = at91_read(priv, AT91_SR);
*reg_sr_p |= reg_sr;
return reg_sr & get_irq_mb_rx(priv);
}
/* interrupt handler
*/
static irqreturn_t at91_irq(int irq, void *dev_id)
{
struct net_device *dev = dev_id;
struct at91_priv *priv = netdev_priv(dev);
irqreturn_t handled = IRQ_NONE;
u32 reg_sr, reg_imr;
reg_sr = at91_read(priv, AT91_SR);
reg_imr = at91_read(priv, AT91_IMR);
/* Ignore masked interrupts */
reg_sr &= reg_imr;
if (!reg_sr)
goto exit;
u32 reg_sr = 0, reg_sr_rx;
int ret;
/* Receive interrupt
* Some bits of AT91_SR are cleared on read, keep them in reg_sr.
*/
while ((reg_sr_rx = at91_get_reg_sr_rx(priv, &reg_sr))) {
ret = can_rx_offload_irq_offload_timestamp(&priv->offload,
reg_sr_rx);
handled = IRQ_HANDLED;
/* Receive interrupt? -> napi */
if (reg_sr & get_irq_mb_rx(priv)) {
at91_write(priv, AT91_IDR,
get_irq_mb_rx(priv));
napi_schedule(&priv->napi);
if (!ret)
break;
}
/* Transmission complete interrupt */
if (reg_sr & get_irq_mb_tx(priv))
if (reg_sr & get_irq_mb_tx(priv)) {
at91_irq_tx(dev, reg_sr);
handled = IRQ_HANDLED;
}
/* Line Error interrupt */
if (reg_sr & AT91_IRQ_ERR_LINE ||
priv->can.state > CAN_STATE_ERROR_ACTIVE) {
at91_irq_err_line(dev, reg_sr);
handled = IRQ_HANDLED;
}
/* Frame Error Interrupt */
if (reg_sr & AT91_IRQ_ERR_FRAME)
if (reg_sr & AT91_IRQ_ERR_FRAME) {
at91_irq_err_frame(dev, reg_sr);
handled = IRQ_HANDLED;
}
if (handled)
can_rx_offload_irq_finish(&priv->offload);
exit:
return handled;
}
......@@ -1040,7 +895,7 @@ static int at91_open(struct net_device *dev)
/* start chip and queuing */
at91_chip_start(dev);
napi_enable(&priv->napi);
can_rx_offload_enable(&priv->offload);
netif_start_queue(dev);
return 0;
......@@ -1062,7 +917,7 @@ static int at91_close(struct net_device *dev)
struct at91_priv *priv = netdev_priv(dev);
netif_stop_queue(dev);
napi_disable(&priv->napi);
can_rx_offload_disable(&priv->offload);
at91_chip_stop(dev, CAN_STATE_STOPPED);
free_irq(dev->irq, dev);
......@@ -1265,8 +1120,11 @@ static int at91_can_probe(struct platform_device *pdev)
priv->clk = clk;
priv->pdata = dev_get_platdata(&pdev->dev);
priv->mb0_id = 0x7ff;
priv->offload.mailbox_read = at91_mailbox_read;
priv->offload.mb_first = devtype_data->rx_first;
priv->offload.mb_last = devtype_data->rx_last;
netif_napi_add_weight(dev, &priv->napi, at91_poll, get_mb_rx_num(priv));
can_rx_offload_add_timestamp(dev, &priv->offload);
if (transceiver)
priv->can.bitrate_max = transceiver->attrs.max_link_rate;
......
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