[U-Boot] [PATCH v2 1/6] usb:gadget:ums: Replace malloc calls with memalign to fix cache buffer alignment

Lukasz Majewski
2014-02-06T06:33:07Z

Hi Marek,

> On Wednesday, February 05, 2014 at 10:10:41 AM, Lukasz Majewski wrote:
> > Calls to malloc() have been replaced by memalign. It now provides
> > proper buffer alignment.
> >
> > Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
> > Cc: Marek Vasut <marex@denx.de>
> >
> > ---
> > Changes for v2:
> > - Remove Change-Id.
> > ---
> > drivers/usb/gadget/f_mass_storage.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/f_mass_storage.c
> > b/drivers/usb/gadget/f_mass_storage.c index b1fe8bd..f896169 100644
> > --- a/drivers/usb/gadget/f_mass_storage.c
> > +++ b/drivers/usb/gadget/f_mass_storage.c
> > @@ -2515,7 +2515,7 @@ static struct fsg_common
> > *fsg_common_init(struct fsg_common *common, buffhds_first_it:
> > bh->inreq_busy = 0;
> > bh->outreq_busy = 0;
> > - bh->buf = kmalloc(FSG_BUFLEN, GFP_KERNEL);
> > + bh->buf = memalign(CONFIG_SYS_CACHELINE_SIZE,
> > FSG_BUFLEN); if (unlikely(!bh->buf)) {
> > rc = -ENOMEM;
> > goto error_release;
> > @@ -2622,7 +2622,7 @@ usb_copy_descriptors(struct
> > usb_descriptor_header **src) bytes += (*tmp)->bLength;
> > bytes += (n_desc + 1) * sizeof(*tmp);
> >
> > - mem = kmalloc(bytes, GFP_KERNEL);
> > + mem = memalign(CONFIG_SYS_CACHELINE_SIZE, bytes);
>
> I wonder, does this align the begining of the buffer as well or only
> the size? Can we rely on the fact the begining is also
> cacheline-aligned ?

In this case, the memalign assures, that beginning of the buffer is
aligned to a cache line.

It is the programmer's responsibility to either have "bytes" aligned to
cache line size or use a wrapper like DEFINE_CACHE_ALIGN_BUFFER().

>
> > if (!mem)
> > return NULL;
>
> Best regards,
> Marek Vasut

--
Best regards,

Lukasz Majewski

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