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Date: Wed, 11 Jan 2012 10:00:42 +0100 From: Wolfgang Zarre <info@...ax.com> To: Wolfgang Grandegger <wg@...ndegger.com> CC: Marc Kleine-Budde <mkl@...gutronix.de>, David Laight <David.Laight@...LAB.COM>, Oliver Hartkopp <socketcan@...tkopp.net>, henrik@...conx.com, netdev@...r.kernel.org, linux-can@...r.kernel.org, socketcan-users@...ts.berlios.de, IreneV <boir1@...dex.ru>, Stanislav Yelenskiy <stanislavelensky@...oo.com>, oe@...t.de, henrik@...us-sw.com Subject: Re: [PATCH net-next v2 2/4] can: cc770: add legacy ISA bus driver for the CC770 and AN82527 Hello Wolfgang, > Hello Wolfgang, > >> On 01/10/2012 12:11 AM, Marc Kleine-Budde wrote: >>> On 01/09/2012 10:47 PM, Wolfgang Zarre wrote: >>> [...] >>> >>>>>> OK. My concern: Can we be sure that 16bit accesses are always >>>>> supported >>>>>> by the hardware? Does a spinlock_irqsave/spinlock_irqrestore around >>>>> the >>>>>> 8bit accesses already help? >>>>> >>>>> Hmmm... are there any register reads that need the >>>>> same 'double cycle' sequence ?? >>>>> If so you need to stop reads being interleaved (with >>>>> themselves and writes) so requesting a 16bit access >>>>> doesn't help. >>>>> >>>>> Which means you need a spinlock... >>>>> >>>>> David >>>>> >>>>> >>>> >>>> @David: Thank You very much for that hint. You are right and to >>>> implement correct we need a spinlock. >>>> >>>> @Wolfgang: I was thinking about Your question regarding 8/16 bit and >>>> in fact it wouldn't work at all on a clean 8 bit cards. >>>> >>>> Further it wouldn't work on 16 bit cards where the MSB is not equal >>>> to base port +1 and anyway, it's depending always on how the chip is >>>> interfaced to the ISA bus and in which mode the chip is configured. >>>> >>>> >>>> And therefore I was giving David's hint a try in using a spinlock in >>>> function cc770_isa_port_write_reg_indirect() and patched as follows: >>>> >>>> --------------------------------------------------------------------- >>>> diff --git a/drivers/net/can/cc770/cc770.c b/drivers/net/can/cc770/cc770.c >>>> index 2d12f89..dad6707 100644 >>>> --- a/drivers/net/can/cc770/cc770.c >>>> +++ b/drivers/net/can/cc770/cc770.c >>>> @@ -460,15 +460,6 @@ static netdev_tx_t cc770_start_xmit(struct sk_buff >>>> *skb, struct net_device *dev) >>>> >>>> stats->tx_bytes += dlc; >>>> >>>> - >>>> - /* >>>> - * HM: We had some cases of repeated IRQs so make sure the >>>> - * INT is acknowledged I know it's already further up, but >>>> - * doing again fixed the issue >>>> - */ >>>> - cc770_write_reg(priv, msgobj[mo].ctrl0, >>>> - MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES); >>>> - >>>> return NETDEV_TX_OK; >>>> } >>>> >>>> @@ -689,12 +680,6 @@ static void cc770_tx_interrupt(struct net_device >>>> *dev, unsigned int o) >>>> /* Nothing more to send, switch off interrupts */ >>>> cc770_write_reg(priv, msgobj[mo].ctrl0, >>>> MSGVAL_RES | TXIE_RES | RXIE_RES | INTPND_RES); >>>> - /* >>>> - * We had some cases of repeated IRQ so make sure the >>>> - * INT is acknowledged >>>> - */ >>>> - cc770_write_reg(priv, msgobj[mo].ctrl0, >>>> - MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES); >> >> Please provide an extra patch for these unrelated changes. If we really >> want to remove it. >> > > Sure, this I can do. > Ok, here the patch to remove: -------------------------------------------------------- diff --git a/drivers/net/can/cc770/cc770.c b/drivers/net/can/cc770/cc770.c index 2d12f89..dad6707 100644 --- a/drivers/net/can/cc770/cc770.c +++ b/drivers/net/can/cc770/cc770.c @@ -460,15 +460,6 @@ static netdev_tx_t cc770_start_xmit(struct sk_buff *skb, struct net_device *dev) stats->tx_bytes += dlc; - - /* - * HM: We had some cases of repeated IRQs so make sure the - * INT is acknowledged I know it's already further up, but - * doing again fixed the issue - */ - cc770_write_reg(priv, msgobj[mo].ctrl0, - MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES); - return NETDEV_TX_OK; } @@ -689,12 +680,6 @@ static void cc770_tx_interrupt(struct net_device *dev, unsigned int o) /* Nothing more to send, switch off interrupts */ cc770_write_reg(priv, msgobj[mo].ctrl0, MSGVAL_RES | TXIE_RES | RXIE_RES | INTPND_RES); - /* - * We had some cases of repeated IRQ so make sure the - * INT is acknowledged - */ - cc770_write_reg(priv, msgobj[mo].ctrl0, - MSGVAL_UNC | TXIE_UNC | RXIE_UNC | INTPND_RES); stats->tx_packets++; can_get_echo_skb(dev, 0); ---------------------------------------------------------- >>>> stats->tx_packets++; >>>> can_get_echo_skb(dev, 0); >>>> diff --git a/drivers/net/can/cc770/cc770_isa.c >>>> b/drivers/net/can/cc770/cc770_isa.c >>>> index 4be5fe2..fe39eed 100644 >>>> --- a/drivers/net/can/cc770/cc770_isa.c >>>> +++ b/drivers/net/can/cc770/cc770_isa.c >>>> @@ -110,6 +110,9 @@ MODULE_PARM_DESC(bcr, "Bus configuration register >>>> (default=0x40 [CBY])"); >>>> #define CC770_IOSIZE 0x20 >>>> #define CC770_IOSIZE_INDIRECT 0x02 >>>> >>>> +/* Spinlock for cc770_isa_port_write_reg_indirect */ >>>> +static DEFINE_SPINLOCK( outb_lock); >>>> + >>> >>> Do we need a global or a per device spin lock? If this should be a per >>> device one, please introduce a cc770_isa_priv and put the spinlock >>> there. Don't forget to initialize the spinlock. >> >> Yes, that's what I was thinking as well but in the ocan driver I find: >> >> /* >> * we need a spinlock here, as the address register looks shared between >> * two PC-ECAN devices. Moreover, we need to protect WRT interrupts >> */ >> >> Looks like wired hardware. Anyway, a global spinlock might be safer. >> > > Hmmm, actually I thought to place the spinlock local because of having > the problem just with the interrupt and not with mutex. > > But if global wouldn't it then better to make an array[MAX_DEV] for the > lock with initialisation in _init or _start? > > But if PC-ECAN works with that configuration? > >> Wolfgang. > > Wolfgang Wolfgang -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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