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dma: swiotlb: Consolidate slab rounding

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Pass the area count explicitly to swiotlb_calc_nslabs() and keep the
calculation separate from updates to the default_nslabs . Move the
default_nslabs update into swiotlb_adjust_nareas().

Round slabs to a power of two even before the area count is initialized.
For early swiotlb_adjust_size() calls, this moves rounding from area
initialization to size adjustment, so early queries see the rounded
size.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
Link: https://lore.kernel.org/r/20260924060756.1325156-3-aneesh.kumar@kernel.org
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Aneesh Kumar K.V (Arm) 2026-09-24 11:37:50 +05:30 committed by Marek Szyprowski
parent 5b944c3674
commit d5093dbca7
1 changed files with 20 additions and 24 deletions
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44
kernel/dma/swiotlb.c
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@ -117,27 +117,20 @@ struct io_tlb_area {
spinlock_t lock;
};
/*
* Round up number of slabs to the next power of 2. The last area is going
* be smaller than the rest if default_nslabs is not power of two.
* The number of slot in an area should be a multiple of IO_TLB_SEGSIZE,
* otherwise a segment may span two or more areas. It conflicts with free
* contiguous slots tracking: free slots are treated contiguous no matter
* whether they cross an area boundary.
*
* Return true if default_nslabs is rounded up.
*/
static bool round_up_default_nslabs(void)
/* Return a power-of-two number of slabs that can be split between areas. */
static unsigned long swiotlb_calc_nslabs(unsigned long size,
unsigned long nareas)
{
if (!default_nareas)
return false;
unsigned long nslabs;
if (default_nslabs < IO_TLB_SEGSIZE * default_nareas)
default_nslabs = IO_TLB_SEGSIZE * default_nareas;
else if (is_power_of_2(default_nslabs))
return false;
default_nslabs = roundup_pow_of_two(default_nslabs);
return true;
nslabs = ALIGN(DIV_ROUND_UP(size, IO_TLB_SIZE), IO_TLB_SEGSIZE);
if (nareas && nslabs < IO_TLB_SEGSIZE * nareas)
nslabs = IO_TLB_SEGSIZE * nareas;
if (!is_power_of_2(nslabs))
nslabs = roundup_pow_of_two(nslabs);
return nslabs;
}
/**
@ -150,6 +143,8 @@ static bool round_up_default_nslabs(void)
*/
static void swiotlb_adjust_nareas(unsigned int nareas)
{
unsigned long nslabs;
if (!nareas)
nareas = 1;
else if (!is_power_of_2(nareas))
@ -158,9 +153,12 @@ static void swiotlb_adjust_nareas(unsigned int nareas)
default_nareas = nareas;
pr_info("area num %d.\n", nareas);
if (round_up_default_nslabs())
nslabs = swiotlb_calc_nslabs(default_nslabs << IO_TLB_SHIFT, nareas);
if (nslabs != default_nslabs) {
default_nslabs = nslabs;
pr_info("SWIOTLB bounce buffer size roundup to %luMB",
(default_nslabs << IO_TLB_SHIFT) >> 20);
}
}
/**
@ -300,10 +298,8 @@ void __init swiotlb_adjust_size(unsigned long size)
if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
return;
size = ALIGN(size, IO_TLB_SIZE);
default_nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
if (round_up_default_nslabs())
size = default_nslabs << IO_TLB_SHIFT;
default_nslabs = swiotlb_calc_nslabs(size, default_nareas);
size = default_nslabs << IO_TLB_SHIFT;
pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
}