Re: [PATCH 02/10] irqchip/gic-v3-its: Consolidate LPI_PENDBASE_SZ usage

[Julien Thierry]

On 24/09/18 11:54, Suzuki K Poulose wrote:
> On 24/09/18 11:50, Julien Thierry wrote:
> > Hi,
> >
> > On 24/09/18 11:33, Suzuki K Poulose wrote:
> > > Hi Marc,
> > >
> > > On 21/09/18 20:59, Marc Zyngier wrote:
> > > > LPI_PENDING_SZ is always used in conjunction with a max(). Let's
> > > > factor this in the definition of the macro, and simplify the rest
> > > > of the code.
> > > >
> > > > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> > > > ---
> > > > Â drivers/irqchip/irq-gic-v3-its.c | 12 ++++--------
> > > > Â 1 file changed, 4 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> > > > b/drivers/irqchip/irq-gic-v3-its.c
> > > > index c2df341ff6fa..ed6aab11e019 100644
> > > > --- a/drivers/irqchip/irq-gic-v3-its.c
> > > > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > > > @@ -62,7 +62,7 @@ static u32 lpi_id_bits;
> > > > ÂÂ */
> > > > Â #define LPI_NRBITSÂÂÂÂÂÂÂ lpi_id_bits
> > > > Â #define LPI_PROPBASE_SZÂÂÂÂÂÂÂ ALIGN(BIT(LPI_NRBITS), SZ_64K)
> > > > -#define LPI_PENDBASE_SZÂÂÂÂÂÂÂ ALIGN(BIT(LPI_NRBITS) / 8, SZ_64K)
> > > > +#define LPI_PENDBASE_SZÂÂÂÂÂÂÂ max_t(u32, SZ_64K, 
> > > > ALIGN(BIT(LPI_NRBITS) / 8, SZ_64K))
> > >
> > > minor nit: The ALIGN() already aligns the given value up to the required
> > > alignment. So, if the LPI_NRBITS is guaranteed to be non-zero,
> > > we could simply drop the max_t().
> >
> > Hmmm, Doesn't ALIGN only aligns down? So if "BIT(LPI_NR_BITS) / 8 < 
> > SZ_64K" (i.e. LPI_NRBITS < 20) The ALIGN(..., SZ_64K) would give 0.
>
> Isn't it the ALIGN_DOWN(), which aligns it down ? Following the kernel
> definitions :
> linux/kernel.h -> uapi/linux/kernel.h
> ALIGN(x,a) =>ÂÂÂÂ __ALIGN_KERNEL(x, a)
>  ÂÂÂÂÂÂÂ \ => __ALIGN_KERNEL_MASK(x, (a -1)
>  ÂÂÂÂÂÂÂ \ => (((x + (a - 1)) & ~ (a - 1))

Oh, yes you're right, made the wrong assumption.
Your suggestion makes sense. Sorry for the noise.

Thanks,

> Cheers
> Suzuki
>
>
> > Thanks,
> >
> > > Rest looks good to me.
> > >
> > > Suzuki
> > >
> > > > Â #define LPI_PROP_DEFAULT_PRIOÂÂÂ 0xa0
> > > > @@ -1924,12 +1924,9 @@ static int its_alloc_collections(struct 
> > > > its_node *its)
> > > > Â static struct page *its_allocate_pending_table(gfp_t gfp_flags)
> > > > Â {
> > > > ÂÂÂÂÂ struct page *pend_page;
> > > > -ÂÂÂ /*
> > > > -ÂÂÂÂ * The pending pages have to be at least 64kB aligned,
> > > > -ÂÂÂÂ * hence the 'max(LPI_PENDBASE_SZ, SZ_64K)' below.
> > > > -ÂÂÂÂ */
> > > > +
> > > > ÂÂÂÂÂ pend_page = alloc_pages(gfp_flags | __GFP_ZERO,
> > > > -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ get_order(max_t(u32, LPI_PENDBASE_SZ, SZ_64K)));
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ get_order(LPI_PENDBASE_SZ));
> > > > ÂÂÂÂÂ if (!pend_page)
> > > > ÂÂÂÂÂÂÂÂÂ return NULL;
> > > > @@ -1941,8 +1938,7 @@ static struct page 
> > > > *its_allocate_pending_table(gfp_t gfp_flags)
> > > > Â static void its_free_pending_table(struct page *pt)
> > > > Â {
> > > > -ÂÂÂ free_pages((unsigned long)page_address(pt),
> > > > -ÂÂÂÂÂÂÂÂÂÂ get_order(max_t(u32, LPI_PENDBASE_SZ, SZ_64K)));
> > > > +ÂÂÂ free_pages((unsigned long)page_address(pt), 
> > > > get_order(LPI_PENDBASE_SZ));
> > > > Â }
> > > > Â static void its_cpu_init_lpis(void)

--
Julien Thierry