On Fri, Jan 28, 2022 at 10:39:49AM +0100, Thomas Zimmermann wrote: > Hi > > Am 28.01.22 um 10:24 schrieb Lucas De Marchi: > > On Fri, Jan 28, 2022 at 09:53:59AM +0100, Thomas Zimmermann wrote: > > > Hi > > > > > > Am 28.01.22 um 09:36 schrieb Lucas De Marchi: > > > > Add a new type, struct iosys_map, to eventually replace > > > > struct dma_buf_map and its helpers defiend in > > > > include/linux/dma-buf-map.h. > > > > > > > > This is mostly a copy of dma-buf-map with the renames in place and > > > > slightly different wording to avoid tying iosys_map to dma-buf: in fact > > > > it's just a shim layer to abstract system memory, that can be accessed > > > > via regular load and store, from IO memory that needs to be acessed via > > > > arch helpers. Over time the dma-buf-map proved useful outside of buffer > > > > sharing among drivers and started to be used in helper functions for > > > > allocation and generic use. See e.g. > > > > > > > > drivers/gpu/drm/drm_gem_shmem_helper.c > > > > drivers/gpu/drm/drm_gem_framebuffer_helper.c > > > > drivers/gpu/drm/drm_fb_helper.c > > > > > > Well, that was the original motivation: framebuffer memory can be > > > located in system or I/O memory, and even change their location. For > > > some architectures this makes difference. IIRC the framebuffer > > > console crashed on sparc64 because we didn't access I/O memory in > > > the correct way. Hence, we added dma_buf_map to return the type of > > > memory from dma_buf_vmap/dma_buf_vunmap. And because everything is > > > tied together, we had quite a bit of churn throughout the DRM/media > > > code. There are > > > > Thanks for the history on this. It's helpful. My motivation for starting > > using dma_buf_map was very similar: i915 is full of direct load/store. > > It works on x86 for IO memory. While testing it on arm64 the story > > was not kind the same. Since we want to support archs other than x86 we > > need to start using some abstractions and dma_buf_map seemed a nice fit > > :) > > > > > still places in DRM where we access the raw pointers within > > > dma_buf_map. We need to clean this up at some point. > > > > at least those are easier to find than just the raw pointers without > > the abstraction > > > > > > > > > > > > > In the i915 driver it's also desired to share the implementation for > > > > integrated graphics, which uses mostly system memory, with discrete > > > > graphics, which may need to access IO memory. > > > > > > > > Once all the drivers using dma_buf_map are converted, the dma_buf_map > > > > can be retired and iosys_map extended to cover new use cases. > > > > > > Wrt the renaming: the old name isn't good and the new one isn't good > > > either. But I don't have strong feelings for either of them. > > > > :(. As the quote: "There are only two hard things in Computer Science: > > cache invalidation and naming things." > > :D > > > > > [ oh, and I'm also having to deal with cache invalidation to properly > > support other archs. ] > > > > At least I had 2 people saying the name was ok. > > > > > > > > > > > > > Signed-off-by: Lucas De Marchi <lucas.demar...@intel.com> > > > > --- > > > > MAINTAINERS | 1 + > > > > include/linux/dma-buf-map.h | 3 + > > > > include/linux/iosys-map.h | 254 ++++++++++++++++++++++++++++++++++++ > > > > 3 files changed, 258 insertions(+) > > > > create mode 100644 include/linux/iosys-map.h > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > index ea3e6c914384..27ebaded85f8 100644 > > > > --- a/MAINTAINERS > > > > +++ b/MAINTAINERS > > > > @@ -5734,6 +5734,7 @@ F: Documentation/driver-api/dma-buf.rst > > > > F: drivers/dma-buf/ > > > > F: include/linux/*fence.h > > > > F: include/linux/dma-buf* > > > > +F: include/linux/iosys-map.h > > > > > > If anything, I'd complain tha twe now have something in dma-buf that > > > isn't obviously connected to dma-buf. > > > > Let's see if others come with a better name > > Maybe we can move that file into some other module? Driver core or memory > management?
Greg tends to be the fallback for random drivers stuff. Maybe also a good idea to move the kerneldoc include to the driver writer's handbook. Or well it's there already, but into a new separate section. Adding Greg for input, also maybe he has a good idea on the bikeshed :-) -Daniel > > Best regards > Thomas > > > > > thanks > > Lucas De Marchi > > > > > > > > Best regards > > > Thomas > > > > > > > F: include/linux/dma-resv.h > > > > K: \bdma_(?:buf|fence|resv)\b > > > > diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h > > > > index 19fa0b5ae5ec..4b4b2930660b 100644 > > > > --- a/include/linux/dma-buf-map.h > > > > +++ b/include/linux/dma-buf-map.h > > > > @@ -263,4 +263,7 @@ static inline void dma_buf_map_incr(struct > > > > dma_buf_map *map, size_t incr) > > > > map->vaddr += incr; > > > > } > > > > +/* Temporary include for API migration */ > > > > +#include <linux/iosys-map.h> > > > > + > > > > #endif /* __DMA_BUF_MAP_H__ */ > > > > diff --git a/include/linux/iosys-map.h b/include/linux/iosys-map.h > > > > new file mode 100644 > > > > index 000000000000..ad1f08f8f97f > > > > --- /dev/null > > > > +++ b/include/linux/iosys-map.h > > > > @@ -0,0 +1,254 @@ > > > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > > > +/* > > > > + * Pointer abstraction for IO/system memory > > > > + */ > > > > + > > > > +#ifndef __IOSYS_MAP_H__ > > > > +#define __IOSYS_MAP_H__ > > > > + > > > > +#include <linux/io.h> > > > > +#include <linux/string.h> > > > > + > > > > +/* Temporary include while user of dma-buf-map are converted to > > > > iosys-map */ > > > > +#include <linux/dma-buf-map.h> > > > > + > > > > +/** > > > > + * DOC: overview > > > > + * > > > > + * When accessing a memory region, depending on the its > > > > location, users may have > > > > + * to access it with I/O operations or memory load/store > > > > operations. For > > > > + * example, copying to system memory could be done with > > > > memcpy(), copying to I/O > > > > + * memory would be done with memcpy_toio(). > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * void *vaddr = ...; // pointer to system memory > > > > + * memcpy(vaddr, src, len); > > > > + * > > > > + * void *vaddr_iomem = ...; // pointer to I/O memory > > > > + * memcpy_toio(vaddr, _iomem, src, len); > > > > + * > > > > + * The user of such pointer may not have information about the > > > > mapping of that > > > > + * region or may want to have a single code path to handle > > > > operations on that > > > > + * buffer, regardless if it's located in system or IO memory. The type > > > > + * :c:type:`struct iosys_map <iosys_map>` and its helpers > > > > abstract that so the > > > > + * buffer can be passed around to other drivers or have > > > > separate duties inside > > > > + * the same driver for allocation, read and write operations. > > > > + * > > > > + * Open-coding access to :c:type:`struct iosys_map <iosys_map>` > > > > is considered > > > > + * bad style. Rather then accessing its fields directly, use > > > > one of the provided > > > > + * helper functions, or implement your own. For example, instances of > > > > + * :c:type:`struct iosys_map <iosys_map>` can be initialized > > > > statically with > > > > + * IOSYS_MAP_INIT_VADDR(), or at runtime with > > > > iosys_map_set_vaddr(). These > > > > + * helpers will set an address in system memory. > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * struct iosys_map map = IOSYS_MAP_INIT_VADDR(0xdeadbeaf); > > > > + * > > > > + * iosys_map_set_vaddr(&map, 0xdeadbeaf); > > > > + * > > > > + * To set an address in I/O memory, use iosys_map_set_vaddr_iomem(). > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * iosys_map_set_vaddr_iomem(&map, 0xdeadbeaf); > > > > + * > > > > + * Instances of struct iosys_map do not have to be cleaned up, but > > > > + * can be cleared to NULL with iosys_map_clear(). Cleared mappings > > > > + * always refer to system memory. > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * iosys_map_clear(&map); > > > > + * > > > > + * Test if a mapping is valid with either iosys_map_is_set() or > > > > + * iosys_map_is_null(). > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * if (iosys_map_is_set(&map) != iosys_map_is_null(&map)) > > > > + * // always true > > > > + * > > > > + * Instances of :c:type:`struct iosys_map <iosys_map>` can be > > > > compared for > > > > + * equality with iosys_map_is_equal(). Mappings that point to > > > > different memory > > > > + * spaces, system or I/O, are never equal. That's even true if > > > > both spaces are > > > > + * located in the same address space, both mappings contain the > > > > same address > > > > + * value, or both mappings refer to NULL. > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * struct iosys_map sys_map; // refers to system memory > > > > + * struct iosys_map io_map; // refers to I/O memory > > > > + * > > > > + * if (iosys_map_is_equal(&sys_map, &io_map)) > > > > + * // always false > > > > + * > > > > + * A set up instance of struct iosys_map can be used to access > > > > or manipulate the > > > > + * buffer memory. Depending on the location of the memory, the > > > > provided helpers > > > > + * will pick the correct operations. Data can be copied into > > > > the memory with > > > > + * iosys_map_memcpy_to(). The address can be manipulated with > > > > iosys_map_incr(). > > > > + * > > > > + * .. code-block:: c > > > > + * > > > > + * const void *src = ...; // source buffer > > > > + * size_t len = ...; // length of src > > > > + * > > > > + * iosys_map_memcpy_to(&map, src, len); > > > > + * iosys_map_incr(&map, len); // go to first byte after the memcpy > > > > + */ > > > > + > > > > +/** > > > > + * struct iosys_map - Pointer to IO/system memory > > > > + * @vaddr_iomem: The buffer's address if in I/O memory > > > > + * @vaddr: The buffer's address if in system memory > > > > + * @is_iomem: True if the buffer is located in I/O > > > > memory, or false > > > > + * otherwise. > > > > + */ > > > > +#define iosys_map dma_buf_map > > > > + > > > > +/** > > > > + * IOSYS_MAP_INIT_VADDR - Initializes struct iosys_map to an > > > > address in system memory > > > > + * @vaddr_: A system-memory address > > > > + */ > > > > +#define IOSYS_MAP_INIT_VADDR(vaddr_) \ > > > > + { \ > > > > + .vaddr = (vaddr_), \ > > > > + .is_iomem = false, \ > > > > + } > > > > + > > > > +/** > > > > + * iosys_map_set_vaddr - Sets a iosys mapping structure to an > > > > address in system memory > > > > + * @map: The iosys_map structure > > > > + * @vaddr: A system-memory address > > > > + * > > > > + * Sets the address and clears the I/O-memory flag. > > > > + */ > > > > +static inline void iosys_map_set_vaddr(struct iosys_map *map, > > > > void *vaddr) > > > > +{ > > > > + map->vaddr = vaddr; > > > > + map->is_iomem = false; > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_set_vaddr_iomem - Sets a iosys mapping structure > > > > to an address in I/O memory > > > > + * @map: The iosys_map structure > > > > + * @vaddr_iomem: An I/O-memory address > > > > + * > > > > + * Sets the address and the I/O-memory flag. > > > > + */ > > > > +static inline void iosys_map_set_vaddr_iomem(struct iosys_map *map, > > > > + void __iomem *vaddr_iomem) > > > > +{ > > > > + map->vaddr_iomem = vaddr_iomem; > > > > + map->is_iomem = true; > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_is_equal - Compares two iosys mapping structures > > > > for equality > > > > + * @lhs: The iosys_map structure > > > > + * @rhs: A iosys_map structure to compare with > > > > + * > > > > + * Two iosys mapping structures are equal if they both refer to > > > > the same type of memory > > > > + * and to the same address within that memory. > > > > + * > > > > + * Returns: > > > > + * True is both structures are equal, or false otherwise. > > > > + */ > > > > +static inline bool iosys_map_is_equal(const struct iosys_map *lhs, > > > > + const struct iosys_map *rhs) > > > > +{ > > > > + if (lhs->is_iomem != rhs->is_iomem) > > > > + return false; > > > > + else if (lhs->is_iomem) > > > > + return lhs->vaddr_iomem == rhs->vaddr_iomem; > > > > + else > > > > + return lhs->vaddr == rhs->vaddr; > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_is_null - Tests for a iosys mapping to be NULL > > > > + * @map: The iosys_map structure > > > > + * > > > > + * Depending on the state of struct iosys_map.is_iomem, tests if the > > > > + * mapping is NULL. > > > > + * > > > > + * Returns: > > > > + * True if the mapping is NULL, or false otherwise. > > > > + */ > > > > +static inline bool iosys_map_is_null(const struct iosys_map *map) > > > > +{ > > > > + if (map->is_iomem) > > > > + return !map->vaddr_iomem; > > > > + return !map->vaddr; > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_is_set - Tests if the iosys mapping has been set > > > > + * @map: The iosys_map structure > > > > + * > > > > + * Depending on the state of struct iosys_map.is_iomem, tests if the > > > > + * mapping has been set. > > > > + * > > > > + * Returns: > > > > + * True if the mapping is been set, or false otherwise. > > > > + */ > > > > +static inline bool iosys_map_is_set(const struct iosys_map *map) > > > > +{ > > > > + return !iosys_map_is_null(map); > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_clear - Clears a iosys mapping structure > > > > + * @map: The iosys_map structure > > > > + * > > > > + * Clears all fields to zero, including struct iosys_map.is_iomem, so > > > > + * mapping structures that were set to point to I/O memory are > > > > reset for > > > > + * system memory. Pointers are cleared to NULL. This is the default. > > > > + */ > > > > +static inline void iosys_map_clear(struct iosys_map *map) > > > > +{ > > > > + if (map->is_iomem) { > > > > + map->vaddr_iomem = NULL; > > > > + map->is_iomem = false; > > > > + } else { > > > > + map->vaddr = NULL; > > > > + } > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_memcpy_to - Memcpy into iosys mapping > > > > + * @dst: The iosys_map structure > > > > + * @src: The source buffer > > > > + * @len: The number of byte in src > > > > + * > > > > + * Copies data into a iosys mapping. The source buffer is in system > > > > + * memory. Depending on the buffer's location, the helper picks > > > > the correct > > > > + * method of accessing the memory. > > > > + */ > > > > +static inline void iosys_map_memcpy_to(struct iosys_map *dst, > > > > const void *src, > > > > + size_t len) > > > > +{ > > > > + if (dst->is_iomem) > > > > + memcpy_toio(dst->vaddr_iomem, src, len); > > > > + else > > > > + memcpy(dst->vaddr, src, len); > > > > +} > > > > + > > > > +/** > > > > + * iosys_map_incr - Increments the address stored in a iosys mapping > > > > + * @map: The iosys_map structure > > > > + * @incr: The number of bytes to increment > > > > + * > > > > + * Increments the address stored in a iosys mapping. Depending on the > > > > + * buffer's location, the correct value will be updated. > > > > + */ > > > > +static inline void iosys_map_incr(struct iosys_map *map, size_t incr) > > > > +{ > > > > + if (map->is_iomem) > > > > + map->vaddr_iomem += incr; > > > > + else > > > > + map->vaddr += incr; > > > > +} > > > > + > > > > +#endif /* __IOSYS_MAP_H__ */ > > > > > > -- > > > Thomas Zimmermann > > > Graphics Driver Developer > > > SUSE Software Solutions Germany GmbH > > > Maxfeldstr. 5, 90409 Nürnberg, Germany > > > (HRB 36809, AG Nürnberg) > > > Geschäftsführer: Ivo Totev > > > > > > > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Ivo Totev -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch