[RFC PATCH 1/2] fsl-mc: Added header file to provide fsl-mc bus iommu group creation

[Nipun Gupta]

> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy at arm.com]
> Sent: Thursday, June 30, 2016 16:26
> To: Nipun Gupta <nipun.gupta at nxp.com>; will.deacon at arm.com; Stuart Yoder
> <stuart.yoder at nxp.com>; iommu at lists.linux-foundation.org; linux-arm-
> kernel at lists.infradead.org
> Cc: Bharat Bhushan <bharat.bhushan at nxp.com>
> Subject: Re: [RFC PATCH 1/2] fsl-mc: Added header file to provide fsl-mc bus
> iommu group creation
> 
> On 29/06/16 18:14, Nipun Gupta wrote:
> > Added a header file fsl_mc_smmu.h to provide basic support of creating
> > an IOMMU group for a fsl-mc type device and also provide helper macro
> > to get the stream ID of fsl-mc tyoe device.
> >
> > Signed-off-by: Nipun Gupta <nipun.gupta at nxp.com>
> > Signed-off-by: Bharat Bhushan <bharat.bhushan at nxp.com>
> > ---
> >  drivers/staging/fsl-mc/include/fsl_mc_smmu.h | 45
> > ++++++++++++++++++++++++++++
> >  1 file changed, 45 insertions(+)
> >  create mode 100644 drivers/staging/fsl-mc/include/fsl_mc_smmu.h
> >
> > diff --git a/drivers/staging/fsl-mc/include/fsl_mc_smmu.h
> > b/drivers/staging/fsl-mc/include/fsl_mc_smmu.h
> > new file mode 100644
> > index 0000000..9dff5ba
> > --- /dev/null
> > +++ b/drivers/staging/fsl-mc/include/fsl_mc_smmu.h
> > @@ -0,0 +1,45 @@
> > +/*
> > + * Copyright (C) 2016 Freescale Semiconductor, Inc.
> > + * Author: Nipun Gupta <nipun.gupta at freescale.com>
> > + *
> > + * This file is licensed under the terms of the GNU General Public
> > + * License version 2. This program is licensed "as is" without any
> > + * warranty of any kind, whether express or implied.
> > + */
> > +
> > +#ifndef _FSL_MC_SMMU_H_
> > +#define _FSL_MC_SMMU_H_
> > +
> > +#include <../drivers/staging/fsl-mc/include/mc.h>
> > +
> > +/* Macro to get the MC device ICID (Stream ID) */ #define
> > +fslmc_dev_streamid(_dev) (to_fsl_mc_device(_dev)->icid)
> 
> Is the the full 15-bit ICID from the MC's point of view, just the 7 bits that are
> actually routed to the SMMU, or the actual stream ID seen by the SMMU? None
> of those three are necessarily the same, and unless it's the third then I don't see
> the point of patches adding incomplete code which isn't going to work.

Hi Robin,

It's the second one where just 7 bits are maintained in the 'fsl_mc_device--->icid' which is programmed in SMMU. Right, once the SMR masking support is there then only these patches would make more sense. 
We have sent these patches to get some early comments and to have you guys well informed beforehand about the changes which we require in the SMMU driver specific to fsl-mc bus :).

Thanks,
Nipun

> 
> > +/* Macro to get the container device of a MC device */ #define
> > +fslmc_cont_dev(_dev) ((to_fsl_mc_device(dev)->flags & \
> > +	FSL_MC_IS_DPRC) ? (_dev) : (_dev->parent))
> > +
> > +/* Macro to check if a device is a container device */ #define
> > +is_cont_dev(_dev) (to_fsl_mc_device(_dev)->flags & FSL_MC_IS_DPRC)
> > +
> > +static struct iommu_group *fslmc_device_group(struct device *dev) {
> > +	struct device *cont_dev = fslmc_cont_dev(dev);
> > +	struct iommu_group *group;
> > +
> > +	/* Container device is responsible for creating the iommu group */
> > +	if (is_cont_dev(dev)) {
> > +		group = iommu_group_alloc();
> > +
> > +		if (IS_ERR(group))
> > +			return NULL;
> > +	} else {
> > +		get_device(cont_dev);
> > +		group = iommu_group_get(cont_dev);
> > +		put_device(cont_dev);
> > +	}
> > +
> > +	return group;
> > +}
> 
> In isolation, though, this part seems perfectly reasonable.
> 
> Robin.
> 
> > +
> > +#endif /* _FSL_MC_SMMU_H_ */
> >