kernel/linux.git/drivers/base/regmap/internal.h, branch v6.6.132

regmap: maple: Provide lockdep (sub)class for maple tree's internal lock

2024-12-14T19:00:01+00:00

[ Upstream commit 1ed9b927e7dd8b8cff13052efe212a8ff72ec51d ] In some cases when using the maple tree register cache, the lockdep validator might complain about invalid deadlocks: [7.131886] Possible interrupt unsafe locking scenario: [7.131890] CPU0 CPU1 [7.131893] ---- ---- [7.131896] lock(&mt->ma_lock); [7.131904] local_irq_disable(); [7.131907] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock); [7.131916] lock(&mt->ma_lock); [7.131925] [7.131928] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock); [7.131936] *** DEADLOCK *** [7.131939] no locks held by swapper/0/0. [7.131944] the shortest dependencies between 2nd lock and 1st lock: [7.131950] -> (&mt->ma_lock){+.+.}-{2:2} { [7.131966] HARDIRQ-ON-W at: [7.131973] lock_acquire+0x200/0x330 [7.131986] _raw_spin_lock+0x50/0x70 [7.131998] regcache_maple_write+0x68/0xe0 [7.132010] regcache_write+0x6c/0x90 [7.132019] _regmap_read+0x19c/0x1d0 [7.132029] _regmap_update_bits+0xc0/0x148 [7.132038] regmap_update_bits_base+0x6c/0xa8 [7.132048] rk8xx_probe+0x22c/0x3d8 [7.132057] rk8xx_spi_probe+0x74/0x88 [7.132065] spi_probe+0xa8/0xe0 [...] [7.132675] } [7.132678] ... key at: [] __key.0+0x0/0x10 [7.132691] ... acquired at: [7.132695] _raw_spin_lock+0x50/0x70 [7.132704] regcache_maple_write+0x68/0xe0 [7.132714] regcache_write+0x6c/0x90 [7.132724] _regmap_read+0x19c/0x1d0 [7.132732] _regmap_update_bits+0xc0/0x148 [7.132741] regmap_field_update_bits_base+0x74/0xb8 [7.132751] vop2_plane_atomic_update+0x480/0x14d8 [rockchipdrm] [7.132820] drm_atomic_helper_commit_planes+0x1a0/0x320 [drm_kms_helper] [...] [7.135112] -> (rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock){-...}-{2:2} { [7.135130] IN-HARDIRQ-W at: [7.135136] lock_acquire+0x200/0x330 [7.135147] _raw_spin_lock_irqsave+0x6c/0x98 [7.135157] regmap_lock_spinlock+0x20/0x40 [7.135166] regmap_read+0x44/0x90 [7.135175] vop2_isr+0x90/0x290 [rockchipdrm] [7.135225] __handle_irq_event_percpu+0x124/0x2d0 In the example above, the validator seems to get the scope of dependencies wrong, since the regmap instance used in rk8xx-spi driver has nothing to do with the instance from vop2. Improve validation by sharing the regmap's lockdep class with the maple tree's internal lock, while also providing a subclass for the latter. Signed-off-by: Cristian Ciocaltea Link: https://patch.msgid.link/20241031-regmap-maple-lockdep-fix-v2-1-06a3710f3623@collabora.com Signed-off-by: Mark Brown Signed-off-by: Sasha Levin

regmap: Add debugfs file for forcing field writes

2023-06-13T12:15:04+00:00

`_regmap_update_bits()` checks if the current register value differs from the new value, and only writes to the register if they differ. When testing hardware drivers, it might be desirable to always force a register write, for example when writing to a `regmap_field`. This enables and simplifies testing and verification of the hardware interaction. For example, when using a hardware mock/simulation model, one can then more easily verify that the driver makes the correct expected register writes during certain events. Add a bool variable `force_write_field` and a corresponding debugfs entry to enable this. Since this feature could interfere with driver operation, guard it with a macro. Signed-off-by: Waqar Hameed Link: https://lore.kernel.org/r/pnd1qifa7sj.fsf@axis.com Signed-off-by: Mark Brown

regmap: Provide basic test coverage for raw I/O

2023-06-12T17:14:53+00:00

Merge series from Mark Brown : Our existing coverage only deals with buses that provide single register read and write operations, extend it to cover raw buses using a similar approach with a RAM backed register map that the tests can inspect to check operations. This coverage could be more complete but provides a good start.

regmap: Don't check for changes in regcache_set_val()

2023-06-12T13:51:07+00:00

The only user of regcache_set_val() ignores the return value so we may as well not bother checking if the value we are trying to set is the same as the value already stored. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230609-regcache-set-val-no-ret-v1-1-9a6932760cf8@kernel.org Signed-off-by: Mark Brown

regmap: maple: Implement block sync for the maple tree cache

2023-06-12T13:51:06+00:00

For register maps where we can write multiple values in a single bus operation it is generally much faster to do so. Improve the performance of maple tree cache syncs on such devices by identifying blocks of adjacent registers that need to be written out and combining them into a single operation. Combining writes does mean that we need to allocate a scratch buffer and format the data into it but it is expected that for most cases where caches are in use the cost of I/O will be much greater than the cost of doing the allocation and format. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230609-regcache-maple-sync-raw-v1-1-8ddeb4e2b9ab@kernel.org Signed-off-by: Mark Brown

regmap: Provide a ram backed regmap with raw support

2023-06-12T13:47:54+00:00

Provide a simple, 16 bit only, RAM backed regmap which supports raw I/O for use in testing. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230610-regcache-raw-kunit-v1-1-583112cd28ac@kernel.org Signed-off-by: Mark Brown

regmap: allow upshifting register addresses before performing operations

2023-04-07T16:28:19+00:00

Similar to the existing reg_downshift mechanism, that is used to translate register addresses on busses that have a smaller address stride, it's also possible to want to upshift register addresses. Such a case was encountered when network PHYs and PCS that usually sit on a MDIO bus (16-bits register with a stride of 1) are integrated directly as memory-mapped devices. Here, the same register layout defined in 802.3 is used, but the register now have a larger stride. Introduce a mechanism to also allow upshifting register addresses. Re-purpose reg_downshift into a more generic, signed reg_shift, whose sign indicates the direction of the shift. To avoid confusion, also introduce macros to explicitly indicate if we want to downshift or upshift. For bisectability, change any use of reg_downshift to use reg_shift. Signed-off-by: Maxime Chevallier Tested-by: Colin Foster Link: https://lore.kernel.org/r/20230407152604.105467-1-maxime.chevallier@bootlin.com Signed-off-by: Mark Brown

regmap: Add maple tree based register cache

2023-04-03T11:53:44+00:00

The current state of the art for sparse register maps is the rbtree cache. This works well for most applications but isn't always ideal for sparser register maps since the rbtree can get deep, requiring a lot of walking. Fortunately the kernel has a data structure intended to address this very problem, the maple tree. Provide an initial implementation of a register cache based on the maple tree to start taking advantage of it. The entries stored in the maple tree are arrays of register values, with the maple tree keys holding the register addresses. We store data in host native format rather than device native format as we do for rbtree, this will be a benefit for devices where we don't marshal data within regmap and simplifies the code but will result in additional CPU overhead when syncing the cache on devices where we do marshal data in regmap. This should work well for a lot of devices, though there's some additional areas that could be looked at such as caching the last accessed entry like we do for rbtree and trying to minimise the maple tree level locking. We should also use bulk writes rather than single register writes when resyncing the cache where possible, even if we don't store in device native format. Very small register maps may continue to to better with rbtree longer term. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230325-regcache-maple-v3-2-23e271f93dc7@kernel.org Signed-off-by: Mark Brown

regmap: Factor out single value register syncing

2023-04-03T11:53:43+00:00

In order to support sparse caches that don't store data in raw format factor out the parts of the raw block sync implementation that deal with writing a single register via _regmap_write(). Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230325-regcache-maple-v3-1-23e271f93dc7@kernel.org Signed-off-by: Mark Brown

regmap: Add RAM backed register map

2023-03-30T11:25:42+00:00

Add a register map that is a simple array of memory, for use in KUnit testing of the framework. This is not exposed in regmap.h since I can't think of a non-test use case, it is purely for use internally. To facilitate testing we track if registers have been read or written to. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230324-regmap-kunit-v2-1-b208801dc2c8@kernel.org