[RFC PATCH v2] dma-coherent: use KiB in DMA allocation logs

[RFC PATCH v2] dma-coherent: use KiB in DMA allocation logs

[Vova Sharaienko]

We are proposing to update DMA reserved memory pool allocation log
messages to display sizes in KiB instead of MiB. Using MiB caused
allocations less than 1 MiB to be logged as 0 MiB due to integer
truncation. KiB provides better precision for smaller memory regions
specified in the Device Tree.

This is currently marked as an RFC because we would like feedback on
a KiB unit change.

Signed-off-by: Vova Sharaienko <sharaienko@google.com>
---
v1: https://lore.kernel.org/all/20260624000516.597555-1-sharaienko@google.com/
Addressed feedback from v1: changed %ld to %llu for size in KiB
to avoid truncation for sizes (which can be 64-bit on a 32-bit kernel)
larger than 4 GiB.

 kernel/dma/coherent.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
index bcdc0f76d2e8..67f9a88ec4fe 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -69,8 +69,8 @@ static struct dma_coherent_mem *dma_init_coherent_memory(phys_addr_t phys_addr,
 	kfree(dma_mem);
 out_unmap_membase:
 	memunmap(mem_base);
-	pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %zd MiB\n",
-		&phys_addr, size / SZ_1M);
+	pr_err("Reserved memory: failed to init DMA memory pool at %pa, size %zu KiB\n",
+		&phys_addr, size / SZ_1K);
 	return ERR_PTR(-ENOMEM);
 }

@@ -384,8 +384,8 @@ static int __init rmem_dma_setup(unsigned long node, struct reserved_mem *rmem)
 	}
 #endif

-	pr_info("Reserved memory: created DMA memory pool at %pa, size %ld MiB\n",
-		&rmem->base, (unsigned long)rmem->size / SZ_1M);
+	pr_info("Reserved memory: created DMA memory pool at %pa, size %llu KiB\n",
+		&rmem->base, (unsigned long long)(rmem->size / SZ_1K));
 	return 0;
 }

--
2.55.0.rc0.799.gd6f94ed593-goog