From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: [PATCH net-next v2 2/4] can: cc770: add legacy ISA bus driver for the CC770 and AN82527 Date: Tue, 10 Jan 2012 15:43:52 +0100 Message-ID: <4F0C4EA8.7060002@grandegger.com> References: <4F0C31F1.20908@essax.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F0C31F1.20908@essax.com> Sender: netdev-owner@vger.kernel.org To: info@essax.com Cc: David Laight , Oliver Hartkopp , henrik@proconx.com, netdev@vger.kernel.org, linux-can@vger.kernel.org, socketcan-users@lists.berlios.de, IreneV , Stanislav Yelenskiy , oe@port.de, henrik@focus-sw.com List-Id: linux-can.vger.kernel.org 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. Wolfgang.