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

[Lukasz Majewski]

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 Calls to malloc() have been replaced by memalign.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 at samsung.com>
> > Cc: Marek Vasut <marex at 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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