On 14.09.2021 17:10, Roman Skakun wrote:
From: Roman Skakun <redacted>
It is possible when default IO TLB size is not
enough to fit a long buffers as described here [1].
This patch makes a way to set this parameter
using cmdline instead of recompiling a kernel.
[1] https://www.xilinx.com/support/answers/72694.html
I'm not convinced the swiotlb use describe there falls under "intended
use" - mapping a 1280x720 framebuffer in a single chunk? (As an aside,
the bottom of this page is also confusing, as following "Then we can
confirm the modified swiotlb size in the boot log:" there is a log
fragment showing the same original size of 64Mb.
quoted hunk ↗ jump to hunk
--- a/arch/mips/cavium-octeon/dma-octeon.c
+++ b/arch/mips/cavium-octeon/dma-octeon.c
@@ -237,7 +237,7 @@ void __init plat_swiotlb_setup(void)
swiotlbsize = 64 * (1<<20);
#endif
swiotlb_nslabs = swiotlbsize >> IO_TLB_SHIFT;
- swiotlb_nslabs = ALIGN(swiotlb_nslabs, IO_TLB_SEGSIZE);
+ swiotlb_nslabs = ALIGN(swiotlb_nslabs, swiotlb_io_seg_size());
In order to be sure to catch all uses like this one (including ones
which make it upstream in parallel to yours), I think you will want
to rename the original IO_TLB_SEGSIZE to e.g. IO_TLB_DEFAULT_SEGSIZE.
quoted hunk ↗ jump to hunk
@@ -81,15 +86,30 @@ static unsigned int max_segment;
static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
static int __init
-setup_io_tlb_npages(char *str)
+setup_io_tlb_params(char *str)
{
+ unsigned long tmp;
+
if (isdigit(*str)) {
- /* avoid tail segment of size < IO_TLB_SEGSIZE */
- default_nslabs =
- ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
+ default_nslabs = simple_strtoul(str, &str, 0);
}
if (*str == ',')
++str;
+
+ /* get max IO TLB segment size */
+ if (isdigit(*str)) {
+ tmp = simple_strtoul(str, &str, 0);
+ if (tmp)
+ io_tlb_seg_size = ALIGN(tmp, IO_TLB_SEGSIZE);
From all I can tell io_tlb_seg_size wants to be a power of 2. Merely
aligning to a multiple of IO_TLB_SEGSIZE isn't going to be enough.
Jan