On 04/22/2014 01:08 PM, Appana Durga Kedareswara Rao wrote: > Hi Marc, > >> -----Original Message----- >> From: Marc Kleine-Budde [mailto:mkl@xxxxxxxxxxxxxx] >> Sent: Tuesday, April 22, 2014 3:57 PM >> To: Appana Durga Kedareswara Rao; wg@xxxxxxxxxxxxxx; Michal Simek; >> grant.likely@xxxxxxxxxx; robh+dt@xxxxxxxxxx >> Cc: linux-can@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-arm- >> kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; >> devicetree@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH v7 1/2] can: xilinx CAN controller support >> >> On 04/22/2014 12:06 PM, Appana Durga Kedareswara Rao wrote: >> >>>> Meanwhile Thomas Gleixner put some effort into the c_can driver and >>>> found some problems in most of the can driver. See comments inline. >>>> >>> Ok will look into that patches >> >> I've commented the relevant parts of your patch. Although more >> background information can be found in the c_can patches. >> > Ok > >>>>> +/** >>>>> + * xcan_tx_interrupt - Tx Done Isr >>>>> + * @ndev: net_device pointer >>>>> + * @isr: Interrupt status register value >>>>> + */ >>>>> +static void xcan_tx_interrupt(struct net_device *ndev, u32 isr) { >>>>> + struct xcan_priv *priv = netdev_priv(ndev); >>>>> + struct net_device_stats *stats = &ndev->stats; >>>>> + >>>>> + while (priv->tx_head - priv->tx_tail > 0) { >>>>> + priv->write_reg(priv, XCAN_ICR_OFFSET, >>>> XCAN_IXR_TXOK_MASK); >>>>> + if (!(isr & XCAN_IXR_TXOK_MASK)) >>>>> + break; >>>> >>>> This looks broken. I assume you have to issue the >> XCAN_IXR_TXOK_MASK- >>>> write once per tx-completed CAN frame. If you enter this loop you >>>> write once, then isr is read, then you write again and may exit this >>>> loop if XCAN_IXR_TXOK_MASK is not set anymore. >> >> Let's assume you have put 3 CAN frames into the TX-queue and we're into >> tx-complete interrupt for the first frame and the other 2 are still not >> completed. >> >> This means the while() loop is not terminated by (priv->tx_head - >> priv->tx_tail > 0), as it can loop 3 times. >> >> What happens is: >> >> - priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK); >> - if (!(isr & XCAN_IXR_TXOK_MASK)) -> no break >> - can_get_echo_skb() >> - ... >> - isr = priv->read_reg(priv, XCAN_ISR_OFFSET); >> - loop -> >> - priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK); >> - if (!(isr & XCAN_IXR_TXOK_MASK)) -> break >> >> So you have 2x write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK), >> but only a single TX completed CAN frame. >> > > Ok now got it :). Thanks for the explanation. > Will modify the loop logic like below. > > while (priv->tx_head - priv->tx_tail > 0) { > if ((isr & XCAN_IXR_TXOK_MASK)) { > priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK); > can_get_echo_skb(ndev, priv->tx_tail % > priv->tx_max); > priv->tx_tail++; > stats->tx_packets++; > } else { > break; > } > > } > Are you ok with this? what about this: while ((priv->tx_head - priv->tx_tail > 0) && (isr & XCAN_IXR_TXOK_MASK)) { [...] isr = priv->read_reg(priv, XCAN_ISR_OFFSET); } or even while ((priv->tx_head - priv->tx_tail > 0) && (priv->read_reg(priv, XCAN_ISR_OFFSET) & XCAN_IXR_TXOK_MASK)) { [...] } 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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