[PATCH 7/9] drm/i915: Use memcpy_from_page() in gt/uc/intel_uc_fw.c

From: Zhao Liu
Date: Mon Oct 17 2022 - 05:33:24 EST


From: Zhao Liu <zhao1.liu@xxxxxxxxx>

The use of kmap_atomic() is being deprecated in favor of
kmap_local_page()[1].

The main difference between atomic and local mappings is that local
mappings doesn't disable page faults or preemption.

In drm/i915/gt/uc/intel_us_fw.c, the function intel_uc_fw_copy_rsa()
just use the mapping to do memory copy so it doesn't need to disable
pagefaults and preemption for mapping. Thus the local mapping without
atomic context (not disable pagefaults / preemption) is enough.

Therefore, intel_uc_fw_copy_rsa() is a function where the use of
memcpy_from_page() with kmap_local_page() in place of memcpy() with
kmap_atomic() is correctly suited.

Convert the calls of memcpy() with kmap_atomic() / kunmap_atomic() to
memcpy_from_page() which uses local mapping to copy.

[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@xxxxxxxxx/T/#u

Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
Signed-off-by: Zhao Liu <zhao1.liu@xxxxxxxxx>
---
Suggested by credits:
Ira: Referred to his task document and suggestions about using
memcpy_from_page() directly.
Fabio: Referred to his boiler plate commit message.
---
drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
index b91ad4aede1f..64d56f175d32 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
@@ -962,16 +962,13 @@ size_t intel_uc_fw_copy_rsa(struct intel_uc_fw *uc_fw, void *dst, u32 max_len)

for_each_sgt_page(page, iter, uc_fw->obj->mm.pages) {
u32 len = min_t(u32, size, PAGE_SIZE - offset);
- void *vaddr;

if (idx > 0) {
idx--;
continue;
}

- vaddr = kmap_atomic(page);
- memcpy(dst, vaddr + offset, len);
- kunmap_atomic(vaddr);
+ memcpy_from_page(dst, page, offset, len);

offset = 0;
dst += len;
--
2.34.1