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Date: Wed, 11 Jan 2012 10:05:46 +0100
From: Wolfgang Zarre <info@...ax.com>
To: Wolfgang Grandegger <wg@...ndegger.com>
CC: 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,
>
> -------- Original Message --------
> Subject: Re: [PATCH net-next v2 2/4] can: cc770: add legacy ISA bus driver for the CC770 and AN82527
> From: Wolfgang Grandegger <wg@...ndegger.com>
> To: info@...ax.com
> Cc: 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
> Date: Tue Jan 10 2012 17:23:59 GMT+0100 (CET)
>
>> Hi Wolfgang,
>>
>> On 01/10/2012 05:13 PM, Wolfgang Zarre wrote:
>>> Hello Wolfgang,
>>>
>>>> On 01/10/2012 01:41 PM, Wolfgang Zarre wrote:
>>>>> Hello David,
>>>>>>
>>>>>>> cc770_isa_port_write_reg_indirect(const struct cc770_priv *priv,
>>>>>>> int reg, u8 val)
>>>>>>> {
>>>>>>> unsigned long base = (unsigned long)priv->reg_base;
>>>>>>> + unsigned long flags;
>>>>>>>
>>>>>>> + spin_lock_irqsave(&outb_lock, flags);
>>>>>>> outb(reg, base);
>>>>>>> outb(val, base + 1);
>>>>>>> + spin_unlock_irqrestore(&outb_lock, flags);
>>>>>>
>>>>>> Is there a 'read_reg_indirect' function??
>>>>>
>>>>> Yes, there is.
>>>>>
>>>>>> If so it also needs to use the same mutex.
>>>>>
>>>>> Actually, I don't think that we have a problem with mutex
>>>>> beside that it's using just one inb() statement but having
>>>>> for sure with an interrupt between both outb() statements which
>>>>> seems to be critical for the cc770.
>>>>
>>>> But the indirect read function also sets the address register before
>>>> reading the data using inb(). This sequence should also not be
>>>> interrupted and therefore we need to synchronize. For the indirect
>>>> access of the SJA1000 we also need to add spinlocks. Wonder why nobody
>>>> complained so far.
>>>
>>> So, if I understand correct that means that inb() can be interrupted
>>> between
>>> setting the address and reading. If this is the case then yes, we need
>>> spinlock if this is not the case then IMHO we wouldn't need or am I wrong?
>>
>> I think we speak about different things. inb() cannot be interrupted but
>> outb() followed by inb(). For indirect accesses we need something like:
>>
>> /* Spinlock for cc770_isa_port_write_reg_indirect */
>> static DEFINE_SPINLOCK(cc770_isa_port_lock);
>>
>> static u8 cc770_isa_port_read_reg_indirect(const struct cc770_priv *priv,
>> int reg)
>> {
>> unsigned long base = (unsigned long)priv->reg_base;
>> unsigned long flags;
>> u8 val;
>>
>> spin_lock_irqsave(&cc770_isa_port_lock, flags);
>> outb(reg, base);
>> val = inb(base + 1);
>> spin_unlock_irqrestore(&cc770_isa_port_lock, flags);
>>
>> return val;
>> }
>>
>> static void cc770_isa_port_write_reg_indirect(const struct cc770_priv *priv,
>> int reg, u8 val)
>> {
>> unsigned long base = (unsigned long)priv->reg_base;
>> unsigned long flags;
>>
>> spin_lock_irqsave(&cc770_isa_port_lock, flags);
>> outb(reg, base);
>> outb(val, base + 1);
>> spin_unlock_irqrestore(&cc770_isa_port_lock, flags);
>> }
>>
>> Hope we are in synch now.
>>
>
> Thanks a lot. Yes, now phase locked and in synch and sorry, by mistake
> I looked at the wrong function (cc770_isa_port_read_reg) in the heat of
> the moment.
>
> Absolutely clear, there we need a spinlock definitely. I'll start another test run
> just to confirm.
>
>
Test was successful, 2.000.000 telegrams again without problems.
Here so far the patch as You suggested:
-------------------------------------------------------------------
diff --git a/drivers/net/can/cc770/cc770_isa.c b/drivers/net/can/cc770/cc770_isa.c
index 4be5fe2..adf3e45 100644
--- a/drivers/net/can/cc770/cc770_isa.c
+++ b/drivers/net/can/cc770/cc770_isa.c
@@ -110,6 +110,10 @@ 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(cc770_isa_port_lock);
+
+
static struct platform_device *cc770_isa_devs[MAXDEV];
static u8 cc770_isa_mem_read_reg(const struct cc770_priv *priv, int reg)
@@ -138,18 +142,26 @@ static u8 cc770_isa_port_read_reg_indirect(const struct cc770_priv *priv,
int reg)
{
unsigned long base = (unsigned long)priv->reg_base;
+ unsigned long flags;
+ u8 val;
+ spin_lock_irqsave(&cc770_isa_port_lock, flags);
outb(reg, base);
- return inb(base + 1);
+ val = inb(base + 1);
+ spin_unlock_irqrestore(&cc770_isa_port_lock, flags);
+ return val;
}
static void cc770_isa_port_write_reg_indirect(const struct cc770_priv *priv,
int reg, u8 val)
{
unsigned long base = (unsigned long)priv->reg_base;
+ unsigned long flags;
+ spin_lock_irqsave(&cc770_isa_port_lock, flags);
outb(reg, base);
outb(val, base + 1);
+ spin_unlock_irqrestore(&cc770_isa_port_lock, flags);
}
static int __devinit cc770_isa_probe(struct platform_device *pdev)
-------------------------------------------------------
>> Wolfgang.
>>
>
> Wolfgang
Wolfgang
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