Re: [linux-sunxi] [PATCH v5 2/2] can: Allwinner A10/A20 CAN Controller support - controller code

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 09/13/2015 02:45 PM, Maxime Ripard wrote:
>> > +static irqreturn_t sunxi_can_interrupt(int irq, void *dev_id)
>> > +{
>> > +	struct net_device *dev = (struct net_device *)dev_id;
>> > +	struct sunxican_priv *priv = netdev_priv(dev);
>> > +	struct net_device_stats *stats = &dev->stats;
>> > +	u8 isrc, status;
>> > +	int n = 0;
>> > +
>> > +	while ((isrc = readl(priv->base + SUNXI_REG_INT_ADDR)) &&
>> > +	       (n < SUNXI_CAN_MAX_IRQ)) {
>> > +		n++;
>> > +		status = readl(priv->base + SUNXI_REG_STA_ADDR);
>> > +
>> > +		if (isrc & SUNXI_INT_WAKEUP)
>> > +			netdev_warn(dev, "wakeup interrupt\n");
>> > +
>> > +		if (isrc & SUNXI_INT_TBUF_VLD) {
>> > +			/* transmission complete interrupt */
>> > +			stats->tx_bytes +=
>> > +			    readl(priv->base +
>> > +				  SUNXI_REG_RBUF_RBACK_START_ADDR) & 0xf;
>> > +			stats->tx_packets++;
>> > +			can_get_echo_skb(dev, 0);
>> > +			netif_wake_queue(dev);
>> > +			can_led_event(dev, CAN_LED_EVENT_TX);
>> > +		}
>> > +		if (isrc & SUNXI_INT_RBUF_VLD) {
>> > +			/* receive interrupt */
>> > +			while (status & SUNXI_STA_RBUF_RDY) {
>> > +				/* RX buffer is not empty */
>> > +				sunxi_can_rx(dev);
>> > +				status = readl(priv->base + SUNXI_REG_STA_ADDR);
>> > +			}
>> > +		}
>> > +		if (isrc &
>> > +		    (SUNXI_INT_DATA_OR | SUNXI_INT_ERR_WRN | SUNXI_INT_BUS_ERR |
>> > +		     SUNXI_INT_ERR_PASSIVE | SUNXI_INT_ARB_LOST)) {
>> > +			/* error interrupt */
>> > +			if (sunxi_can_err(dev, isrc, status))
>> > +				break;
>> > +		}
>> > +		/* clear interrupts */
>> > +		writel(isrc, priv->base + SUNXI_REG_INT_ADDR);
>> > +		readl(priv->base + SUNXI_REG_INT_ADDR);
>> > +	}
> Why not simply handle whatever you have in the status register, and
> let the interrupt retrigger if there's something new?

Latency. On CAN Networks you can have an interrupt rate of sevel KHz.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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