RE: [PATCH v10 3/5] CPM/QE: use genalloc to manage CPM/QE muram

Zhao Qiang
2015-09-23T02:21:00Z

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On Wen, Sep 23, 2015 at 8:19 AM +0800, Wood Scott-B07421 wrote:

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Wednesday, September 23, 2015 8:19 AM
> To: Zhao Qiang-B45475
> Cc: linux-kernel@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
> lauraa@codeaurora.org; Xie Xiaobo-R63061; benh@kernel.crashing.org; Li
> Yang-Leo-R58472; paulus@samba.org
> Subject: Re: [PATCH v10 3/5] CPM/QE: use genalloc to manage CPM/QE muram
>
> On Tue, 2015-09-22 at 03:10 -0500, Zhao Qiang-B45475 wrote:
> > On Tue, Sep 22, 2015 at 06:47 AM +0800, Wood Scott-B07421 wrote:
> > > -----Original Message-----
> > > From: Wood Scott-B07421
> > > Sent: Tuesday, September 22, 2015 6:47 AM
> > > To: Zhao Qiang-B45475
> > > Cc: linux-kernel@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
> > > lauraa@codeaurora.org; Xie Xiaobo-R63061; benh@kernel.crashing.org;
> > > Li Yang-Leo-R58472; paulus@samba.org
> > > Subject: Re: [PATCH v10 3/5] CPM/QE: use genalloc to manage CPM/QE
> > > muram
> > >
> > > On Fri, Sep 18, 2015 at 03:15:19PM +0800, Zhao Qiang wrote:
> > > > Use genalloc to manage CPM/QE muram instead of rheap.
> > > >
> > > > Signed-off-by: Zhao Qiang <qiang.zhao@freescale.com>
> > > > ---
> > > > Changes for v9:
> > > > - splitted from patch 3/5, modify cpm muram management functions.
> > > > Changes for v10:
> > > > - modify cpm muram first, then move to qe_common
> > > > - modify commit.
> > > >
> > > > arch/powerpc/platforms/Kconfig | 1 +
> > > > arch/powerpc/sysdev/cpm_common.c | 150
> > > > +++++++++++++++++++++++++++------------
> > > > 2 files changed, 107 insertions(+), 44 deletions(-)
> > > >
> > > > diff --git a/arch/powerpc/platforms/Kconfig
> > > > b/arch/powerpc/platforms/Kconfig index b7f9c40..01f98a2 100644
> > > > --- a/arch/powerpc/platforms/Kconfig
> > > > +++ b/arch/powerpc/platforms/Kconfig
> > > > @@ -276,6 +276,7 @@ config QUICC_ENGINE
> > > > bool "Freescale QUICC Engine (QE) Support"
> > > > depends on FSL_SOC && PPC32
> > > > select PPC_LIB_RHEAP
> > > > + select GENERIC_ALLOCATOR
> > > > select CRC32
> > > > help
> > > > The QUICC Engine (QE) is a new generation of communications
> > > > diff --git a/arch/powerpc/sysdev/cpm_common.c
> > > > b/arch/powerpc/sysdev/cpm_common.c
> > > > index 4f78695..453d18c 100644
> > > > --- a/arch/powerpc/sysdev/cpm_common.c
> > > > +++ b/arch/powerpc/sysdev/cpm_common.c
> > > > @@ -17,6 +17,7 @@
> > > > * published by the Free Software Foundation.
> > > > */
> > > >
> > > > +#include <linux/genalloc.h>
> > > > #include <linux/init.h>
> > > > #include <linux/of_device.h>
> > > > #include <linux/spinlock.h>
> > > > @@ -27,7 +28,6 @@
> > > >
> > > > #include <asm/udbg.h>
> > > > #include <asm/io.h>
> > > > -#include <asm/rheap.h>
> > > > #include <asm/cpm.h>
> > > >
> > > > #include <mm/mmu_decl.h>
> > > > @@ -65,14 +65,24 @@ void __init udbg_init_cpm(void) } #endif
> > > >
> > > > +static struct gen_pool *muram_pool; static struct
> > > > +genpool_data_align muram_pool_data; static struct
> > > > +genpool_data_fixed muram_pool_data_fixed;
> > >
> > > Why are these global? If you keep the data local to the caller (and
> > > use
> > > gen_pool_alloc_data()) then you probably don't need cpm_muram_lock.
> >
> > Ok
> >
> > >
> > > > static spinlock_t cpm_muram_lock; -static rh_block_t
> > > > cpm_boot_muram_rh_block[16]; -static rh_info_t cpm_muram_info;
> > > > static u8 __iomem *muram_vbase; static phys_addr_t muram_pbase;
> > > >
> > > > -/* Max address size we deal with */
> > > > +struct muram_block {
> > > > + struct list_head head;
> > > > + unsigned long start;
> > > > + int size;
> > > > +};
> > > > +
> > > > +static LIST_HEAD(muram_block_list);
> > > > +
> > > > +/* max address size we deal with */
> > > > #define OF_MAX_ADDR_CELLS 4
> > > > +#define GENPOOL_OFFSET 4096
> > >
> > > Is 4096 bytes the maximum alignment you'll ever need? Wouldn't it
> > > be safer to use a much larger offset?
> >
> > Yes, 4096 is the maximum alignment I ever need.
>
> Still, I'd be more comfortable with a larger offset.

Larger offset is good.

>
> Better yet would be using gen_pool_add_virt() and using virtual addresses
> for the allocations, similar to http://patchwork.ozlabs.org/patch/504000/
>
> > > > int cpm_muram_init(void)
> > > > {
> > > > @@ -86,113 +96,165 @@ int cpm_muram_init(void)
> > > > if (muram_pbase)
> > > > return 0;
> > > >
> > > > - spin_lock_init(&cpm_muram_lock);
> > >
> > > Why are you eliminating the lock init, given that you're not getting
> > > rid of the lock?
> > >
> > > > - /* initialize the info header */
> > > > - rh_init(&cpm_muram_info, 1,
> > > > - sizeof(cpm_boot_muram_rh_block) /
> > > > - sizeof(cpm_boot_muram_rh_block[0]),
> > > > - cpm_boot_muram_rh_block);
> > > > -
> > > > np = of_find_compatible_node(NULL, NULL, "fsl,cpm-muram-data");
> > > > if (!np) {
> > > > /* try legacy bindings */
> > > > np = of_find_node_by_name(NULL, "data-only");
> > > > if (!np) {
> > > > - printk(KERN_ERR "Cannot find CPM muram data
> node");
> > > > + pr_err("Cannot find CPM muram data node");
> > > > ret = -ENODEV;
> > > > goto out;
> > > > }
> > > > }
> > > >
> > > > + muram_pool = gen_pool_create(1, -1);
> > >
> > > Do we really need byte-granularity?
> >
> > It is 2byte-granularity, 4byte-granularity is needed
> >
> > >
> > > > muram_pbase = of_translate_address(np, zero);
> > > > if (muram_pbase == (phys_addr_t)OF_BAD_ADDR) {
> > > > - printk(KERN_ERR "Cannot translate zero through CPM muram
> > > node");
> > > > + pr_err("Cannot translate zero through CPM muram node");
> > > > ret = -ENODEV;
> > > > - goto out;
> > > > + goto err;
> > > > }
> > > >
> > > > while (of_address_to_resource(np, i++, &r) == 0) {
> > > > if (r.end > max)
> > > > max = r.end;
> > > > + ret = gen_pool_add(muram_pool, r.start - muram_pbase +
> > > > + GENPOOL_OFFSET, resource_size(&r), -1);
> > > > + if (ret) {
> > > > + pr_err("QE: couldn't add muram to
> pool!\n");
> > > > + goto err;
> > > > + }
> > > >
> > > > - rh_attach_region(&cpm_muram_info, r.start - muram_pbase,
> > > > - resource_size(&r));
> > > > }
> > > >
> > > > muram_vbase = ioremap(muram_pbase, max - muram_pbase + 1);
> > > > if (!muram_vbase) {
> > > > - printk(KERN_ERR "Cannot map CPM muram");
> > > > + pr_err("Cannot map QE muram");
> > > > ret = -ENOMEM;
> > > > + goto err;
> > > > }
> > > > -
> > > > + goto out;
> > > > +err:
> > > > + gen_pool_destroy(muram_pool);
> > > > out:
> > > > of_node_put(np);
> > > > return ret;
> > >
> > > Having both "err" and "out" is confusing. Instead call it
> > > "out_pool" or similar.
> >
> > Ok
> >
> > > > {
> > > > - int ret;
> > > > +
> > > > + unsigned long start;
> > > > unsigned long flags;
> > > > + unsigned long size_alloc = size; struct muram_block *entry; int
> > > > + end_bit; int order = muram_pool->min_alloc_order;
> > > >
> > > > spin_lock_irqsave(&cpm_muram_lock, flags);
> > > > - ret = rh_free(&cpm_muram_info, offset);
> > > > + end_bit = (offset >> order) + ((size + (1UL << order) - 1) >>
> > > order);
> > > > + if ((offset + size) > (end_bit << order))
> > > > + size_alloc = size + (1UL << order);
> > >
> > > Why do you need to do all these calculations here?
> >
> > So do it in gen_pool_fixed_alloc?
>
> Could you explain why they're needed at all?

Why it does the calculations?
If the min block of gen_pool is 8 bytes, and I want to allocate a
Region with offset=7, size=8bytes, I actually need block 0 and block 1,
And the allocation will give me block 0.

>
> > gen_pool_fixed_alloc just
> > Can see numbers of blocks. It can't do calculations in
> gen_pool_fixed_alloc.
>
> Are you saying that this:
>
> struct genpool_data_fixed {
> unsigned long offset; /* The offset of the specific
> region */
> };
>
> refers to blocks and not bytes? And you didn't even mention that in the
> comment?

Offset is bytes.

>
> It should be bytes. Actually, it should be an address, not an offset.
> It should be the same value that you receive back from the allocator.
> And I'm not sure how this is going to work with genalloc chunks that
> don't start at zero. I think it really does need to be a separate
> toplevel function, and not just an allocation algorithm (or else the
> allocation algorithm is going to need more context on what chunk it's
> working on).
>
> Speaking of chunks and the allocation function, I wonder what happens if
> you hit "if (start_bit >= end_bit) continue;" and then enter the loop
> with a new chunk and start_bit != 0...
>
> -Scott

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