[PATCH 13/16] drivers: misc: add ARM CCI support

[Nicolas Pitre]

On Fri, 11 Jan 2013, Santosh Shilimkar wrote:

> On Thursday 10 January 2013 05:50 AM, Nicolas Pitre wrote:
> > From: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > 
> > On ARM multi-cluster systems coherency between cores running on
> > different clusters is managed by the cache-coherent interconnect (CCI).
> > It allows broadcasting of TLB invalidates and memory barriers and it
> > guarantees cache coherency at system level.
> > 
> > This patch enables the basic infrastructure required in Linux to
> > handle and programme the CCI component. The first implementation is
> > based on a platform device, its relative DT compatible property and
> > a simple programming interface.
> > 
> > Signed-off-by: Nicolas Pitre <nico at linaro.org>
> > ---
> >   drivers/misc/Kconfig    |   3 ++
> >   drivers/misc/Makefile   |   1 +
> >   drivers/misc/arm-cci.c  | 107
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> >   include/linux/arm-cci.h |  30 ++++++++++++++
> How about 'drivers/bus/' considering CCI is an interconnect bus (though
> for coherency)

Yes, I like that better.

> >   4 files changed, 141 insertions(+)
> >   create mode 100644 drivers/misc/arm-cci.c
> >   create mode 100644 include/linux/arm-cci.h
> > 
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index b151b7c1bd..30d5be1ad2 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -499,6 +499,9 @@ config USB_SWITCH_FSA9480
> >   	  stereo and mono audio, video, microphone and UART data to use
> >   	  a common connector port.
> > 
> > +config ARM_CCI
> You might want add depends on ARM big.LITTTLE otherwise it will
> break build for other arch's with random configurations.

As far as this patch goes, this is buildable on other architectures too.  
The next patch changes that though.

> [..]
> 
> > diff --git a/drivers/misc/arm-cci.c b/drivers/misc/arm-cci.c
> > new file mode 100644
> > index 0000000000..f329c43099
> > --- /dev/null
> > +++ b/drivers/misc/arm-cci.c
> > @@ -0,0 +1,107 @@
> > +/*
> > + * CCI support
> > + *
> > + * Copyright (C) 2012 ARM Ltd.
> > + * Author: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> > + * kind, whether express or implied; without even the implied warranty
> > + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/device.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/slab.h>
> > +#include <linux/arm-cci.h>
> > +
> > +#define CCI400_EAG_OFFSET       0x4000
> > +#define CCI400_KF_OFFSET        0x5000
> > +
> > +#define DRIVER_NAME	"CCI"
> > +struct cci_drvdata {
> > +	void __iomem *baseaddr;
> > +	spinlock_t lock;
> > +};
> > +
> > +static struct cci_drvdata *info;
> > +
> > +void disable_cci(int cluster)
> > +{
> > +	u32 cci_reg = cluster ? CCI400_KF_OFFSET : CCI400_EAG_OFFSET;
> > +	writel_relaxed(0x0, info->baseaddr	+ cci_reg);
> > +
> > +	while (readl_relaxed(info->baseaddr + 0xc) & 0x1)
> > +			;
> > +}
> > +EXPORT_SYMBOL_GPL(disable_cci);
> > +
> Is more functionality going to be added for CCI driver. Having this
> much of driver code for just a disable_cci() functions seems like
> overkill.

Yes.  More code will appear here to provide pmu functionalities, etc.


Nicolas