RE: [PATCH] powerpc/44x: Support OCM(On Chip Memory) for APM821xx SoC and Bluestone board

[Vinh Huu Tuong Nguyen <vhtnguyen@apm.com>]

> -----Original Message-----
> From: Josh Boyer [mailto:jwboyer@gmail.com]
> Sent: Friday, June 15, 2012 12:47 AM
> To: Vinh Nguyen Huu Tuong
> Cc: Benjamin Herrenschmidt; Paul Mackerras; Matt Porter; Grant Likely;
> Rob Herring; Duc Dang; David S. Miller; Kumar Gala; Li Yang; Ashish
> Kalra; Anatolij Gustschin; Liu Gang; linuxppc-dev@lists.ozlabs.org;
> linux-kernel@vger.kernel.org; devicetree-discuss@lists.ozlabs.org
> Subject: Re: [PATCH] powerpc/44x: Support OCM(On Chip Memory) for
> APM821xx SoC and Bluestone board
>
> On Sun, May 6, 2012 at 11:52 PM, Vinh Nguyen Huu Tuong
> <vhtnguyen@apm.com> wrote:
> > This patch consists of:
> > - Add driver for OCM component
> > - Export OCM Information at /sys/class/ocm/ocminfo
>
> Again, apologies for the delay.  Aside from the incorrect sysfs usage I
> pointed out in my other reply, I have just a few comments/questions
> below.
[Vinh Nguyen] You're welcome. About the files on sysfs, the first place of
ocm is in procfs, but procfs is deprecated and replaced by sysfs, then I
decided to move it to sysfs. With your comments, I think I can move it to
debugfs.
>
> > diff --git a/arch/powerpc/boot/dts/bluestone.dts
> > b/arch/powerpc/boot/dts/bluestone.dts
> > index 7bda373..2687c11 100644
> > --- a/arch/powerpc/boot/dts/bluestone.dts
> > +++ b/arch/powerpc/boot/dts/bluestone.dts
> > @@ -107,6 +107,14 @@
> >                interrupt-parent = <&UIC0>;
> >        };
> >
> > +       OCM1: ocm@400040000 {
> > +               compatible = "ibm,ocm";
> > +               status = "ok";
> > +               cell-index = <1>;
> > +               /* configured in U-Boot */
> > +               reg = <4 0x00040000 0x8000>; /* 32K */
> > +       };
> > +
> >        SDR0: sdr {
> >                compatible = "ibm,sdr-apm821xx";
> >                dcr-reg = <0x00e 0x002>; diff --git
> > a/arch/powerpc/include/asm/ppc4xx_ocm.h
> > b/arch/powerpc/include/asm/ppc4xx_ocm.h
> > new file mode 100644
> > index 0000000..ff7f386
> > --- /dev/null
> > +++ b/arch/powerpc/include/asm/ppc4xx_ocm.h
> > @@ -0,0 +1,47 @@
> > +/*
> > + * PowerPC 4xx OCM memory allocation support
> > + *
> > + * (C) Copyright 2009, Applied Micro Circuits Corporation
> > + * Victor Gallardo (vgallardo@amcc.com)
> > + *
> > + * See file CREDITS for list of people who contributed to this
> > + * project.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation; either version 2 of
> > + * the License, or (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write to the Free Software
> > + * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
> > + * MA 02111-1307 USA
> > + */
> > +
> > +#ifndef __ASM_POWERPC_PPC4xx_OCM_H__
> > +#define __ASM_POWERPC_PPC4xx_OCM_H__
> > +
> > +#include <linux/types.h>
> > +
> > +#define OCM_NON_CACHED 0
> > +#define OCM_CACHED     1
> > +
> > +#if defined(CONFIG_PPC4xx_OCM)
> > +
> > +void *ocm_alloc(phys_addr_t *phys, int size, int align,
> > +                 int flags, const char *owner); void ocm_free(const
> > +void *virt);
> > +
> > +#else
> > +
> > +#define ocm_alloc(phys, size, align, flags, owner)     NULL #define
> > +ocm_free(addr) ((void)0)
> > +
> > +#endif /* CONFIG_PPC4xx_OCM */
> > +
> > +#endif  /* __ASM_POWERPC_PPC4xx_OCM_H__ */
>
> I don't see any users of this header included in the patch.  I'm going
> to guess that follow-on drivers/users are queued once this is in the
> tree?  Also, you might want to name these 'ppc4xx_ocm_alloc' or
> similar.  The concept of OCM isn't limited to ppc4xx or even SoCs, so
> just using 'ocm' in the global kernel namespace might not be great.
>
[Vinh Nguyen] With our plan, the next submit of IBM NEW EMAC will use it
for speedup. About the naming convention, I will change as your comments.

> > diff --git a/arch/powerpc/sysdev/ppc4xx_ocm.c
> > b/arch/powerpc/sysdev/ppc4xx_ocm.c
> > new file mode 100644
> > index 0000000..ba3e450
> > --- /dev/null
> > +++ b/arch/powerpc/sysdev/ppc4xx_ocm.c
> > @@ -0,0 +1,420 @@
> > +#include <linux/kernel.h>
> > +#include <linux/errno.h>
> > +#include <linux/proc_fs.h>
>
> Why do you need proc_fs.h?
[Vinh Nguyen] I will remove it.
>
> > +#include <linux/seq_file.h>
> > +#include <linux/spinlock.h>
> > +#include <linux/dma-mapping.h>
> > +#include <linux/list.h>
> > +#include <asm/uaccess.h>
> > +#include <asm/prom.h>
> > +#include <asm/dcr.h>
> > +#include <asm/rheap.h>
> > +#include <asm/mmu.h>
> > +#include <asm/ppc4xx_ocm.h>
> > +#include <linux/export.h>
> > +
> > +#define OCM_DISABLED   0
> > +#define OCM_ENABLED            1
> > +
> > +struct ocm_block {
> > +       struct list_head        list;
> > +       void __iomem            *addr;
> > +       int                                     size;
> > +       const char                      *owner; };
> > +
> > +/* non-cached or cached region */
> > +struct ocm_region {
> > +       phys_addr_t                     phys;
> > +       void __iomem            *virt;
> > +
> > +       int                                     memtotal;
> > +       int                                     memfree;
> > +
> > +       rh_info_t                       *rh;
> > +       struct list_head        list;
> > +};
>
> There's some interesting whitespace usage in these struct definitions.
[Vinh Nguyen] I'll check again and remove them. I used the scripts check
in kernel but it can't remove them all.
>
> josh

I'll update the patch soon but I need send out to internal review first
before sending out to community. It takes one or two week, please be
patient for the next review.

Best regards,
Vinh Nguyen