From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukas Wunner Subject: Re: [PATCH] can: hi311x: Work around TX complete interrupt erratum Date: Thu, 10 May 2018 06:38:43 +0200 Message-ID: <20180510043843.GA14936@wunner.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mathias Duckeck , Akshay Bhat , Casey Fitzpatrick To: Marc Kleine-Budde , Wolfgang Grandegger , linux-can@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from bmailout1.hostsharing.net ([83.223.95.100]:38471 "EHLO bmailout1.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756373AbeEJEip (ORCPT ); Thu, 10 May 2018 00:38:45 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, May 09, 2018 at 02:43:43PM +0200, Lukas Wunner wrote: > When sending packets as fast as possible using "cangen -g 0 -i -x", the > HI-3110 occasionally latches the interrupt pin high on completion of a > packet, but doesn't set the TXCPLT bit in the INTF register. The INTF > register contains 0x00 as if no interrupt has occurred. Even waiting > for a few milliseconds after the interrupt doesn't help. > > Work around this apparent erratum by instead checking the TXMTY bit in > the STATF register ("TX FIFO empty"). We know that we've queued up a > packet for transmission if priv->tx_len is nonzero. If the TX FIFO is > empty, transmission of that packet must have completed. > > Note that this is congruent with our handling of received packets, which > likewise gleans from the STATF register whether a packet is waiting in > the RX FIFO, instead of looking at the INTF register. I should have mentioned, to verify the existence of the erratum and the validity of the patch, you can apply the little debug patch below, then run "cangen -g 0 -i -x". You should see error messages in dmesg within a few minutes. -- >8 -- diff --git a/drivers/net/can/spi/hi311x.c b/drivers/net/can/spi/hi311x.c index 53e320c..48b5c63 100644 --- a/drivers/net/can/spi/hi311x.c +++ b/drivers/net/can/spi/hi311x.c @@ -739,6 +739,9 @@ static irqreturn_t hi3110_can_ist(int irq, void *dev_id) } if (priv->tx_len && statf & HI3110_STAT_TXMTY) { + if (!(intf & HI3110_INT_TXCPLT)) + dev_err(&spi->dev, "TX FIFO empty and TX was queued but TXCPLT not set\n"); + net->stats.tx_packets++; net->stats.tx_bytes += priv->tx_len - 1; can_led_event(net, CAN_LED_EVENT_TX);