diff options
Diffstat (limited to 'debian/patches-rt/0044-Documentation-io-mapping-Remove-outdated-blurb.patch')
| -rw-r--r-- | debian/patches-rt/0044-Documentation-io-mapping-Remove-outdated-blurb.patch | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/debian/patches-rt/0044-Documentation-io-mapping-Remove-outdated-blurb.patch b/debian/patches-rt/0044-Documentation-io-mapping-Remove-outdated-blurb.patch new file mode 100644 index 000000000..4ea660fff --- /dev/null +++ b/debian/patches-rt/0044-Documentation-io-mapping-Remove-outdated-blurb.patch @@ -0,0 +1,48 @@ +From edd5c644d78fbd912f6386c97ed2b4eaf2b58b47 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Tue, 3 Nov 2020 10:27:33 +0100 +Subject: [PATCH 044/323] Documentation/io-mapping: Remove outdated blurb +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +The implementation details in the documentation are outdated and not really +helpful. Remove them. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + Documentation/driver-api/io-mapping.rst | 22 ---------------------- + 1 file changed, 22 deletions(-) + +diff --git a/Documentation/driver-api/io-mapping.rst b/Documentation/driver-api/io-mapping.rst +index a966239f04e4..e33b88268554 100644 +--- a/Documentation/driver-api/io-mapping.rst ++++ b/Documentation/driver-api/io-mapping.rst +@@ -73,25 +73,3 @@ for pages mapped with io_mapping_map_wc. + At driver close time, the io_mapping object must be freed:: + + void io_mapping_free(struct io_mapping *mapping) +- +-Current Implementation +-====================== +- +-The initial implementation of these functions uses existing mapping +-mechanisms and so provides only an abstraction layer and no new +-functionality. +- +-On 64-bit processors, io_mapping_create_wc calls ioremap_wc for the whole +-range, creating a permanent kernel-visible mapping to the resource. The +-map_atomic and map functions add the requested offset to the base of the +-virtual address returned by ioremap_wc. +- +-On 32-bit processors with HIGHMEM defined, io_mapping_map_atomic_wc uses +-kmap_atomic_pfn to map the specified page in an atomic fashion; +-kmap_atomic_pfn isn't really supposed to be used with device pages, but it +-provides an efficient mapping for this usage. +- +-On 32-bit processors without HIGHMEM defined, io_mapping_map_atomic_wc and +-io_mapping_map_wc both use ioremap_wc, a terribly inefficient function which +-performs an IPI to inform all processors about the new mapping. This results +-in a significant performance penalty. +-- +2.43.0 + |