Re: [PATCH v4 3/8] MIPS: Octeon: Add a global resource manager.

[David Daney]

On 11/30/2017 02:53 PM, James Hogan wrote:
> On Tue, Nov 28, 2017 at 04:55:35PM -0800, David Daney wrote:
> > From: Carlos Munoz <cmunoz@xxxxxxxxxx>
> >
> > Add a global resource manager to manage tagged pointers within
> > bootmem allocated memory. This is used by various functional
> > blocks in the Octeon core like the FPA, Ethernet nexus, etc.
> >
> > Signed-off-by: Carlos Munoz <cmunoz@xxxxxxxxxx>
> > Signed-off-by: Steven J. Hill <Steven.Hill@xxxxxxxxxx>
> > Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> > ---
> >   arch/mips/cavium-octeon/Makefile       |   3 +-
> >   arch/mips/cavium-octeon/resource-mgr.c | 371 +++++++++++++++++++++++++++++++++
> >   arch/mips/include/asm/octeon/octeon.h  |  18 ++
> >   3 files changed, 391 insertions(+), 1 deletion(-)
> >   create mode 100644 arch/mips/cavium-octeon/resource-mgr.c
> >
> > diff --git a/arch/mips/cavium-octeon/Makefile b/arch/mips/cavium-octeon/Makefile
> > index 7c02e542959a..0a299ab8719f 100644
> > --- a/arch/mips/cavium-octeon/Makefile
> > +++ b/arch/mips/cavium-octeon/Makefile
> > @@ -9,7 +9,8 @@
> >   # Copyright (C) 2005-2009 Cavium Networks
> >   #
> >   
> > -obj-y := cpu.o setup.o octeon-platform.o octeon-irq.o csrc-octeon.o
> > +obj-y := cpu.o setup.o octeon-platform.o octeon-irq.o csrc-octeon.o \
> > +	 resource-mgr.o
>
> Maybe put that on a separate line like below.

OK

> >   obj-y += dma-octeon.o
> >   obj-y += octeon-memcpy.o
> >   obj-y += executive/
> > diff --git a/arch/mips/cavium-octeon/resource-mgr.c b/arch/mips/cavium-octeon/resource-mgr.c
> > new file mode 100644
> > index 000000000000..ca25fa953402
> > --- /dev/null
> > +++ b/arch/mips/cavium-octeon/resource-mgr.c
> > @@ -0,0 +1,371 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Resource manager for Octeon.
> > + *
> > + * This file is subject to the terms and conditions of the GNU General Public
> > + * License.  See the file "COPYING" in the main directory of this archive
> > + * for more details.
> > + *
> > + * Copyright (C) 2017 Cavium, Inc.
> > + */
> > +#include <linux/module.h>
> > +
> > +#include <asm/octeon/octeon.h>
> > +#include <asm/octeon/cvmx-bootmem.h>
> > +
> > +#define RESOURCE_MGR_BLOCK_NAME		"cvmx-global-resources"
> > +#define MAX_RESOURCES			128
> > +#define INST_AVAILABLE			-88
> > +#define OWNER				0xbadc0de
> > +
> > +struct global_resource_entry {
> > +	struct global_resource_tag tag;
> > +	u64 phys_addr;
> > +	u64 size;
> > +};
> > +
> > +struct global_resources {
> > +#ifdef __LITTLE_ENDIAN_BITFIELD
> > +	u32 rlock;
> > +	u32 pad;
> > +#else
> > +	u32 pad;
> > +	u32 rlock;
> > +#endif
> > +	u64 entry_cnt;
> > +	struct global_resource_entry resource_entry[];
> > +};
> > +
> > +static struct global_resources *res_mgr_info;
> > +
> > +
> > +/*
> > + * The resource manager interacts with software running outside of the
> > + * Linux kernel, which necessitates locking to maintain data structure
> > + * consistency.  These custom locking functions implement the locking
> > + * protocol, and cannot be replaced by kernel locking functions that
> > + * may use different in-memory structures.
> > + */
> > +
> > +static void res_mgr_lock(void)
> > +{
> > +	unsigned int tmp;
> > +	u64 lock = (u64)&res_mgr_info->rlock;
>
> presumably this could be a u32 *, avoid the cast to u64, and still work
> just fine below.

I will rewrite to just use cmpxchg()


> > +
> > +	__asm__ __volatile__(
> > +		".set noreorder\n"
> > +		"1: ll   %[tmp], 0(%[addr])\n"
> > +		"   bnez %[tmp], 1b\n"
> > +		"   li   %[tmp], 1\n"
>
> I believe the convention for .S files is for instructions in branch
> delay slots to be indented an additional space for readability. Maybe
> that would be worthwhile here.
>
> > +		"   sc   %[tmp], 0(%[addr])\n"
> > +		"   beqz %[tmp], 1b\n"
> > +		"   nop\n"
>
> and here also.
>
> > +		".set reorder\n" :
>
> nit: strictly speaking there's no need for \n on the last line.
>
> > +		[tmp] "=&r"(tmp) :
> > +		[addr] "r"(lock) :
> > +		"memory");
>
> minor style thing: its far more common to have : at the beginning of the
> line rather than the end.
>
> > +}
> > +
> > +static void res_mgr_unlock(void)
> > +{
> > +	u64 lock = (u64)&res_mgr_info->rlock;
>
> same again

Will rewrite to use WRITE_ONCE().

> > +
> > +	/* Wait until all resource operations finish before unlocking. */
> > +	mb();
> > +	__asm__ __volatile__(
> > +		"sw $0, 0(%[addr])\n" : :
> > +		[addr] "r"(lock) :
> > +		"memory");
> > +
> > +	/* Force a write buffer flush. */
> > +	mb();
> > +}
> > +
> > +static int res_mgr_find_resource(struct global_resource_tag tag)
> > +{
> > +	struct global_resource_entry *res_entry;
> > +	int i;
> > +
> > +	for (i = 0; i < res_mgr_info->entry_cnt; i++) {
> > +		res_entry = &res_mgr_info->resource_entry[i];
> > +		if (res_entry->tag.lo == tag.lo && res_entry->tag.hi == tag.hi)
> > +			return i;
> > +	}
> > +	return -1;
> > +}
> > +
> > +/**
> > + * res_mgr_create_resource - Create a resource.
> > + * @tag: Identifies the resource.
> > + * @inst_cnt: Number of resource instances to create.
> > + *
> > + * Returns 0 if the source was created successfully.
> > + * Returns <0 for error codes.
>
> Only -1 seems to be returned. Is it worth returning some standard Linux
> error codes instead?

Yep.  I fixed this and everything below for the next version of the 
patch set.

Thanks,
David Daney