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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-22 12:04:39 -0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-22 12:04:39 -0400 |
| commit | d0440c59f52d31aa7f74ba8e35cc22ee96acea84 (patch) | |
| tree | 199470b64cdc30e9f0f7ecd5286ff7cc2e0a969d /Documentation/arm | |
| parent | 38eb1dbb0d7d190bdfe2ea824e94dab19e32737f (diff) | |
| parent | c4c14f393fe4991a423c21516511ff1011140143 (diff) | |
Merge tag 'armsoc-cleanup' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
Pull ARM SoC cleanups from Olof Johansson:
"We've got a fairly large cleanup branch this time. The bulk of this
is removal of non-DT platforms of several flavors:
- Atmel at91 platforms go full-DT, with removal of remaining
board-file based support
- OMAP removes legacy board files for three more platforms
- removal of non-DT mach-msm, newer Qualcomm platforms now live in
mach-qcom
- Freescale i.MX25 also removes non-DT platform support"
Most of the rest of the changes here are fallout from the above, i.e. for
example removal of drivers that now lack platforms, etc.
* tag 'armsoc-cleanup' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (58 commits)
mmc: Remove msm_sdcc driver
gpio: Remove gpio-msm-v1 driver
ARM: Remove mach-msm and associated ARM architecture code
ARM: shmobile: cpuidle: Remove the pointless default driver
ARM: davinci: dm646x: Add interrupt resource for McASPs
ARM: davinci: irqs: Correct McASP1 TX interrupt definition for DM646x
ARM: davinci: dm646x: Clean up the McASP DMA resources
ARM: davinci: devices-da8xx: Add support for McASP2 on da830
ARM: davinci: devices-da8xx: Clean up and correct the McASP device creation
ARM: davinci: devices-da8xx: Add interrupt resource to McASP structs
ARM: davinci: devices-da8xx: Add resource name for the McASP DMA request
ARM: OMAP2+: Remove legacy support for omap3 TouchBook
ARM: OMAP3: Remove legacy support for devkit8000
ARM: OMAP3: Remove legacy support for EMA-Tech Stalker board
ARM: shmobile: Consolidate the pm code for R-Car Gen2
ARM: shmobile: r8a7791: Correct SYSCIER value
ARM: shmobile: r8a7790: Correct SYSCIER value
ARM: at91: remove old setup
ARM: at91: sama5d4: remove useless map_io
ARM: at91: sama5 use SoC detection infrastructure
...
Diffstat (limited to 'Documentation/arm')
| -rw-r--r-- | Documentation/arm/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/arm/msm/gpiomux.txt | 176 |
2 files changed, 0 insertions, 178 deletions
diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index 8edb9007844e..dea011c8d7c7 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX | |||
| @@ -10,8 +10,6 @@ IXP4xx | |||
| 10 | - Intel IXP4xx Network processor. | 10 | - Intel IXP4xx Network processor. |
| 11 | Makefile | 11 | Makefile |
| 12 | - Build sourcefiles as part of the Documentation-build for arm | 12 | - Build sourcefiles as part of the Documentation-build for arm |
| 13 | msm/ | ||
| 14 | - MSM specific documentation | ||
| 15 | Netwinder | 13 | Netwinder |
| 16 | - Netwinder specific documentation | 14 | - Netwinder specific documentation |
| 17 | Porting | 15 | Porting |
diff --git a/Documentation/arm/msm/gpiomux.txt b/Documentation/arm/msm/gpiomux.txt deleted file mode 100644 index 67a81620adf6..000000000000 --- a/Documentation/arm/msm/gpiomux.txt +++ /dev/null | |||
| @@ -1,176 +0,0 @@ | |||
| 1 | This document provides an overview of the msm_gpiomux interface, which | ||
| 2 | is used to provide gpio pin multiplexing and configuration on mach-msm | ||
| 3 | targets. | ||
| 4 | |||
| 5 | History | ||
| 6 | ======= | ||
| 7 | |||
| 8 | The first-generation API for gpio configuration & multiplexing on msm | ||
| 9 | is the function gpio_tlmm_config(). This function has a few notable | ||
| 10 | shortcomings, which led to its deprecation and replacement by gpiomux: | ||
| 11 | |||
| 12 | The 'disable' parameter: Setting the second parameter to | ||
| 13 | gpio_tlmm_config to GPIO_CFG_DISABLE tells the peripheral | ||
| 14 | processor in charge of the subsystem to perform a look-up into a | ||
| 15 | low-power table and apply the low-power/sleep setting for the pin. | ||
| 16 | As the msm family evolved this became problematic. Not all pins | ||
| 17 | have sleep settings, not all peripheral processors will accept requests | ||
| 18 | to apply said sleep settings, and not all msm targets have their gpio | ||
| 19 | subsystems managed by a peripheral processor. In order to get consistent | ||
| 20 | behavior on all targets, drivers are forced to ignore this parameter, | ||
| 21 | rendering it useless. | ||
| 22 | |||
| 23 | The 'direction' flag: for all mux-settings other than raw-gpio (0), | ||
| 24 | the output-enable bit of a gpio is hard-wired to a known | ||
| 25 | input (usually VDD or ground). For those settings, the direction flag | ||
| 26 | is meaningless at best, and deceptive at worst. In addition, using the | ||
| 27 | direction flag to change output-enable (OE) directly can cause trouble in | ||
| 28 | gpiolib, which has no visibility into gpio direction changes made | ||
| 29 | in this way. Direction control in gpio mode should be made through gpiolib. | ||
| 30 | |||
| 31 | Key Features of gpiomux | ||
| 32 | ======================= | ||
| 33 | |||
| 34 | - A consistent interface across all generations of msm. Drivers can expect | ||
| 35 | the same results on every target. | ||
| 36 | - gpiomux plays nicely with gpiolib. Functions that should belong to gpiolib | ||
| 37 | are left to gpiolib and not duplicated here. gpiomux is written with the | ||
| 38 | intent that gpio_chips will call gpiomux reference-counting methods | ||
| 39 | from their request() and free() hooks, providing full integration. | ||
| 40 | - Tabular configuration. Instead of having to call gpio_tlmm_config | ||
| 41 | hundreds of times, gpio configuration is placed in a single table. | ||
| 42 | - Per-gpio sleep. Each gpio is individually reference counted, allowing only | ||
| 43 | those lines which are in use to be put in high-power states. | ||
| 44 | - 0 means 'do nothing': all flags are designed so that the default memset-zero | ||
| 45 | equates to a sensible default of 'no configuration', preventing users | ||
| 46 | from having to provide hundreds of 'no-op' configs for unused or | ||
| 47 | unwanted lines. | ||
| 48 | |||
| 49 | Usage | ||
| 50 | ===== | ||
| 51 | |||
| 52 | To use gpiomux, provide configuration information for relevant gpio lines | ||
| 53 | in the msm_gpiomux_configs table. Since a 0 equates to "unconfigured", | ||
| 54 | only those lines to be managed by gpiomux need to be specified. Here | ||
| 55 | is a completely fictional example: | ||
| 56 | |||
| 57 | struct msm_gpiomux_config msm_gpiomux_configs[GPIOMUX_NGPIOS] = { | ||
| 58 | [12] = { | ||
| 59 | .active = GPIOMUX_VALID | GPIOMUX_DRV_8MA | GPIOMUX_FUNC_1, | ||
| 60 | .suspended = GPIOMUX_VALID | GPIOMUX_PULL_DOWN, | ||
| 61 | }, | ||
| 62 | [34] = { | ||
| 63 | .suspended = GPIOMUX_VALID | GPIOMUX_PULL_DOWN, | ||
| 64 | }, | ||
| 65 | }; | ||
| 66 | |||
| 67 | To indicate that a gpio is in use, call msm_gpiomux_get() to increase | ||
| 68 | its reference count. To decrease the reference count, call msm_gpiomux_put(). | ||
| 69 | |||
| 70 | The effect of this configuration is as follows: | ||
| 71 | |||
| 72 | When the system boots, gpios 12 and 34 will be initialized with their | ||
| 73 | 'suspended' configurations. All other gpios, which were left unconfigured, | ||
| 74 | will not be touched. | ||
| 75 | |||
| 76 | When msm_gpiomux_get() is called on gpio 12 to raise its reference count | ||
| 77 | above 0, its active configuration will be applied. Since no other gpio | ||
| 78 | line has a valid active configuration, msm_gpiomux_get() will have no | ||
| 79 | effect on any other line. | ||
| 80 | |||
| 81 | When msm_gpiomux_put() is called on gpio 12 or 34 to drop their reference | ||
| 82 | count to 0, their suspended configurations will be applied. | ||
| 83 | Since no other gpio line has a valid suspended configuration, no other | ||
| 84 | gpio line will be effected by msm_gpiomux_put(). Since gpio 34 has no valid | ||
| 85 | active configuration, this is effectively a no-op for gpio 34 as well, | ||
| 86 | with one small caveat, see the section "About Output-Enable Settings". | ||
| 87 | |||
| 88 | All of the GPIOMUX_VALID flags may seem like unnecessary overhead, but | ||
| 89 | they address some important issues. As unused entries (all those | ||
| 90 | except 12 and 34) are zero-filled, gpiomux needs a way to distinguish | ||
| 91 | the used fields from the unused. In addition, the all-zero pattern | ||
| 92 | is a valid configuration! Therefore, gpiomux defines an additional bit | ||
| 93 | which is used to indicate when a field is used. This has the pleasant | ||
| 94 | side-effect of allowing calls to msm_gpiomux_write to use '0' to indicate | ||
| 95 | that a value should not be changed: | ||
| 96 | |||
| 97 | msm_gpiomux_write(0, GPIOMUX_VALID, 0); | ||
| 98 | |||
| 99 | replaces the active configuration of gpio 0 with an all-zero configuration, | ||
| 100 | but leaves the suspended configuration as it was. | ||
| 101 | |||
| 102 | Static Configurations | ||
| 103 | ===================== | ||
| 104 | |||
| 105 | To install a static configuration, which is applied at boot and does | ||
| 106 | not change after that, install a configuration with a suspended component | ||
| 107 | but no active component, as in the previous example: | ||
| 108 | |||
| 109 | [34] = { | ||
| 110 | .suspended = GPIOMUX_VALID | GPIOMUX_PULL_DOWN, | ||
| 111 | }, | ||
| 112 | |||
| 113 | The suspended setting is applied during boot, and the lack of any valid | ||
| 114 | active setting prevents any other setting from being applied at runtime. | ||
| 115 | If other subsystems attempting to access the line is a concern, one could | ||
| 116 | *really* anchor the configuration down by calling msm_gpiomux_get on the | ||
| 117 | line at initialization to move the line into active mode. With the line | ||
| 118 | held, it will never be re-suspended, and with no valid active configuration, | ||
| 119 | no new configurations will be applied. | ||
| 120 | |||
| 121 | But then, if having other subsystems grabbing for the line is truly a concern, | ||
| 122 | it should be reserved with gpio_request instead, which carries an implicit | ||
| 123 | msm_gpiomux_get. | ||
| 124 | |||
| 125 | gpiomux and gpiolib | ||
| 126 | =================== | ||
| 127 | |||
| 128 | It is expected that msm gpio_chips will call msm_gpiomux_get() and | ||
| 129 | msm_gpiomux_put() from their request and free hooks, like this fictional | ||
| 130 | example: | ||
| 131 | |||
| 132 | static int request(struct gpio_chip *chip, unsigned offset) | ||
| 133 | { | ||
| 134 | return msm_gpiomux_get(chip->base + offset); | ||
| 135 | } | ||
| 136 | |||
| 137 | static void free(struct gpio_chip *chip, unsigned offset) | ||
| 138 | { | ||
| 139 | msm_gpiomux_put(chip->base + offset); | ||
| 140 | } | ||
| 141 | |||
| 142 | ...somewhere in a gpio_chip declaration... | ||
| 143 | .request = request, | ||
| 144 | .free = free, | ||
| 145 | |||
| 146 | This provides important functionality: | ||
| 147 | - It guarantees that a gpio line will have its 'active' config applied | ||
| 148 | when the line is requested, and will not be suspended while the line | ||
| 149 | remains requested; and | ||
| 150 | - It guarantees that gpio-direction settings from gpiolib behave sensibly. | ||
| 151 | See "About Output-Enable Settings." | ||
| 152 | |||
| 153 | This mechanism allows for "auto-request" of gpiomux lines via gpiolib | ||
| 154 | when it is suitable. Drivers wishing more exact control are, of course, | ||
| 155 | free to also use msm_gpiomux_set and msm_gpiomux_get. | ||
| 156 | |||
| 157 | About Output-Enable Settings | ||
| 158 | ============================ | ||
| 159 | |||
| 160 | Some msm targets do not have the ability to query the current gpio | ||
| 161 | configuration setting. This means that changes made to the output-enable | ||
| 162 | (OE) bit by gpiolib cannot be consistently detected and preserved by gpiomux. | ||
| 163 | Therefore, when gpiomux applies a configuration setting, any direction | ||
| 164 | settings which may have been applied by gpiolib are lost and the default | ||
| 165 | input settings are re-applied. | ||
| 166 | |||
| 167 | For this reason, drivers should not assume that gpio direction settings | ||
| 168 | continue to hold if they free and then re-request a gpio. This seems like | ||
| 169 | common sense - after all, anybody could have obtained the line in the | ||
| 170 | meantime - but it needs saying. | ||
| 171 | |||
| 172 | This also means that calls to msm_gpiomux_write will reset the OE bit, | ||
| 173 | which means that if the gpio line is held by a client of gpiolib and | ||
| 174 | msm_gpiomux_write is called, the direction setting has been lost and | ||
| 175 | gpiolib's internal state has been broken. | ||
| 176 | Release gpio lines before reconfiguring them. | ||
