On 4/29/19 2:03 PM, Jeroen Hofstee wrote: > As already mentioned in [1] and included in [2], there is an off by one > issue since the high bank is already enabled when the _next_ mailbox to > be read has index 12, so the mailbox being read was 13. The message can > therefore go into mailbox 31 and the driver will be repolled until the > mailbox 12 eventually receives a msg. Or the message might end up in the > 12th mailbox, but then it would become disabled after reading it and only > be enabled again in the next "round" after mailbox 13 was read, which can > cause out of order messages, since the lower priority mailboxes can > accept messages in the meantime. > > As mentioned in [3] there is a hardware race condition when changing the > CANME register while messages are being received. Even when including a > busy poll on reception, like in [2] there are still overflows and out of > order messages at times, but less then without the busy loop polling. > Unlike what the patch suggests, the polling time is not in the microsecond > range, but takes as long as a current CAN bus reception needs to finish, > so typically more in the fraction of millisecond range. Since the timeout > is in jiffies it won't timeout. > > Even with these additional fixes the driver is still not able to provide a > proper FIFO which doesn't drop packages. So change the driver to use > rx-offload and base order on timestamp instead of message box numbers. As > a side affect, this also fixes [4] and [5]. > > Before this change messages with a single byte counter were dropped / > received out of order at a bitrate of 250kbit/s on an am3517. With this > patch that no longer occurs up to and including 1Mbit/s. > > [1] > https://linux-can.vger.kernel.narkive.com/zgO9inVi/patch-can-ti-hecc-fix-rx-wrong-sequence-issue#post6 > [2] > http://arago-project.org/git/projects/?p=linux-omap3.git;a=commit;h=02346892777f07245de4d5af692513ebd852dcb2 > [3] > https://linux-can.vger.kernel.narkive.com/zgO9inVi/patch-can-ti-hecc-fix-rx-wrong-sequence-issue#post5 > [4] https://patchwork.ozlabs.org/patch/895956/ > [5] https://www.spinics.net/lists/netdev/msg494971.html > > Cc: Anant Gole <[email protected]> > Cc: AnilKumar Ch <[email protected]> > Signed-off-by: Jeroen Hofstee <[email protected]>
[...]
> @@ -744,8 +652,8 @@ static irqreturn_t ti_hecc_interrupt(int irq, void
> *dev_id)
> struct net_device *ndev = (struct net_device *)dev_id;
> struct ti_hecc_priv *priv = netdev_priv(ndev);
> struct net_device_stats *stats = &ndev->stats;
> - u32 mbxno, mbx_mask, int_status, err_status;
> - unsigned long ack, flags;
> + u32 mbxno, mbx_mask, int_status, err_status, stamp;
> + unsigned long flags, rx_pending;
>
> int_status = hecc_read(priv,
> (priv->use_hecc1int) ? HECC_CANGIF1 : HECC_CANGIF0);
> @@ -769,11 +677,11 @@ static irqreturn_t ti_hecc_interrupt(int irq, void
> *dev_id)
> spin_lock_irqsave(&priv->mbx_lock, flags);
> hecc_clear_bit(priv, HECC_CANME, mbx_mask);
> spin_unlock_irqrestore(&priv->mbx_lock, flags);
> - stats->tx_bytes += hecc_read_mbx(priv, mbxno,
> - HECC_CANMCF) & 0xF;
> + stamp = hecc_read_stamp(priv, mbxno);
> + stats->tx_bytes +=
> can_rx_offload_get_echo_skb(&priv->offload,
> + mbxno,
> stamp);
> stats->tx_packets++;
> can_led_event(ndev, CAN_LED_EVENT_TX);
> - can_get_echo_skb(ndev, mbxno);
> --priv->tx_tail;
> }
>
> @@ -784,12 +692,11 @@ static irqreturn_t ti_hecc_interrupt(int irq, void
> *dev_id)
> ((priv->tx_head & HECC_TX_MASK) == HECC_TX_MASK)))
> netif_wake_queue(ndev);
>
> - /* Disable RX mailbox interrupts and let NAPI reenable them */
> - if (hecc_read(priv, HECC_CANRMP)) {
> - ack = hecc_read(priv, HECC_CANMIM);
> - ack &= BIT(HECC_MAX_TX_MBOX) - 1;
> - hecc_write(priv, HECC_CANMIM, ack);
> - napi_schedule(&priv->napi);
> + /* offload RX mailboxes and let NAPI deliver them */
> + while ((rx_pending = hecc_read(priv, HECC_CANRMP))) {
> + can_rx_offload_irq_offload_timestamp(&priv->offload,
> + rx_pending);
> + hecc_write(priv, HECC_CANRMP, rx_pending);
Can prepare a patch to move the RMP writing into the mailbox_read()
function. This makes the mailbox available a bit earlier and works
better for memory pressure situations, where no skb can be allocated.
> }
> }
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Industrial Linux Solutions | Phone: +49-231-2826-924 |
Vertretung West/Dortmund | Fax: +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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