summaryrefslogtreecommitdiff
path: root/Documentation/pwm.txt
diff options
context:
space:
mode:
authorScott Wood <scottwood@freescale.com>2013-12-14 01:15:24 (GMT)
committerScott Wood <scottwood@freescale.com>2013-12-14 01:15:24 (GMT)
commitb7c81aa3ab2ac2c140e278b6d0e9a0b95112cf0b (patch)
tree87828aaf5f82c7042bfc0307bc4ac499e10f93fb /Documentation/pwm.txt
parent22c782a4b14773fab7eab3c1db54ad7ad077e9b8 (diff)
parent78fd82238d0e5716578c326404184a27ba67fd6e (diff)
downloadlinux-fsl-qoriq-b7c81aa3ab2ac2c140e278b6d0e9a0b95112cf0b.tar.xz
Merge remote-tracking branch 'linus/master' into merge
Conflicts: Documentation/hwmon/ina2xx arch/powerpc/Kconfig arch/powerpc/boot/dts/b4860emu.dts arch/powerpc/boot/dts/b4qds.dtsi arch/powerpc/boot/dts/fsl/b4si-post.dtsi arch/powerpc/boot/dts/fsl/qoriq-sec6.0-0.dtsi arch/powerpc/boot/dts/p1023rdb.dts arch/powerpc/boot/dts/t4240emu.dts arch/powerpc/boot/dts/t4240qds.dts arch/powerpc/configs/85xx/p1023_defconfig arch/powerpc/configs/corenet32_smp_defconfig arch/powerpc/configs/corenet64_smp_defconfig arch/powerpc/configs/mpc85xx_smp_defconfig arch/powerpc/include/asm/cputable.h arch/powerpc/include/asm/device.h arch/powerpc/include/asm/epapr_hcalls.h arch/powerpc/include/asm/kvm_host.h arch/powerpc/include/asm/mpic.h arch/powerpc/include/asm/pci.h arch/powerpc/include/asm/ppc-opcode.h arch/powerpc/include/asm/ppc_asm.h arch/powerpc/include/asm/reg_booke.h arch/powerpc/kernel/epapr_paravirt.c arch/powerpc/kernel/process.c arch/powerpc/kernel/prom.c arch/powerpc/kernel/setup-common.c arch/powerpc/kernel/setup_32.c arch/powerpc/kernel/setup_64.c arch/powerpc/kernel/smp.c arch/powerpc/kernel/swsusp_asm64.S arch/powerpc/kernel/swsusp_booke.S arch/powerpc/kvm/book3s_pr.c arch/powerpc/kvm/booke.c arch/powerpc/kvm/booke.h arch/powerpc/kvm/e500.c arch/powerpc/kvm/e500.h arch/powerpc/kvm/e500_emulate.c arch/powerpc/kvm/e500mc.c arch/powerpc/kvm/powerpc.c arch/powerpc/perf/e6500-pmu.c arch/powerpc/platforms/85xx/Kconfig arch/powerpc/platforms/85xx/Makefile arch/powerpc/platforms/85xx/b4_qds.c arch/powerpc/platforms/85xx/c293pcie.c arch/powerpc/platforms/85xx/corenet_ds.c arch/powerpc/platforms/85xx/corenet_ds.h arch/powerpc/platforms/85xx/p1023_rds.c arch/powerpc/platforms/85xx/p2041_rdb.c arch/powerpc/platforms/85xx/p3041_ds.c arch/powerpc/platforms/85xx/p4080_ds.c arch/powerpc/platforms/85xx/p5020_ds.c arch/powerpc/platforms/85xx/p5040_ds.c arch/powerpc/platforms/85xx/smp.c arch/powerpc/platforms/85xx/t4240_qds.c arch/powerpc/platforms/Kconfig arch/powerpc/sysdev/Makefile arch/powerpc/sysdev/fsl_mpic_timer_wakeup.c arch/powerpc/sysdev/fsl_msi.c arch/powerpc/sysdev/fsl_pci.c arch/powerpc/sysdev/fsl_pci.h arch/powerpc/sysdev/fsl_soc.h arch/powerpc/sysdev/mpic.c arch/powerpc/sysdev/mpic_timer.c drivers/Kconfig drivers/clk/Kconfig drivers/clk/clk-ppc-corenet.c drivers/cpufreq/Kconfig.powerpc drivers/cpufreq/Makefile drivers/cpufreq/ppc-corenet-cpufreq.c drivers/crypto/caam/Kconfig drivers/crypto/caam/Makefile drivers/crypto/caam/ctrl.c drivers/crypto/caam/desc_constr.h drivers/crypto/caam/intern.h drivers/crypto/caam/jr.c drivers/crypto/caam/regs.h drivers/dma/fsldma.c drivers/hwmon/ina2xx.c drivers/iommu/Kconfig drivers/iommu/fsl_pamu.c drivers/iommu/fsl_pamu.h drivers/iommu/fsl_pamu_domain.c drivers/iommu/fsl_pamu_domain.h drivers/misc/Makefile drivers/mmc/card/block.c drivers/mmc/core/core.c drivers/mmc/host/sdhci-esdhc.h drivers/mmc/host/sdhci-pltfm.c drivers/mtd/nand/fsl_ifc_nand.c drivers/net/ethernet/freescale/gianfar.c drivers/net/ethernet/freescale/gianfar.h drivers/net/ethernet/freescale/gianfar_ethtool.c drivers/net/phy/at803x.c drivers/net/phy/phy_device.c drivers/net/phy/vitesse.c drivers/pci/msi.c drivers/staging/Kconfig drivers/staging/Makefile drivers/uio/Kconfig drivers/uio/Makefile drivers/uio/uio.c drivers/usb/host/ehci-fsl.c drivers/vfio/Kconfig drivers/vfio/Makefile include/crypto/algapi.h include/linux/iommu.h include/linux/mmc/sdhci.h include/linux/msi.h include/linux/netdev_features.h include/linux/phy.h include/linux/skbuff.h include/net/ip.h include/uapi/linux/vfio.h net/core/ethtool.c net/ipv4/route.c net/ipv6/route.c
Diffstat (limited to 'Documentation/pwm.txt')
-rw-r--r--Documentation/pwm.txt41
1 files changed, 39 insertions, 2 deletions
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 7d2b4c9..93cb979 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -39,12 +39,49 @@ New users should use the pwm_get() function and pass to it the consumer
device or a consumer name. pwm_put() is used to free the PWM device. Managed
variants of these functions, devm_pwm_get() and devm_pwm_put(), also exist.
-After being requested a PWM has to be configured using:
+After being requested, a PWM has to be configured using:
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
+Using PWMs with the sysfs interface
+-----------------------------------
+
+If CONFIG_SYSFS is enabled in your kernel configuration a simple sysfs
+interface is provided to use the PWMs from userspace. It is exposed at
+/sys/class/pwm/. Each probed PWM controller/chip will be exported as
+pwmchipN, where N is the base of the PWM chip. Inside the directory you
+will find:
+
+npwm - The number of PWM channels this chip supports (read-only).
+
+export - Exports a PWM channel for use with sysfs (write-only).
+
+unexport - Unexports a PWM channel from sysfs (write-only).
+
+The PWM channels are numbered using a per-chip index from 0 to npwm-1.
+
+When a PWM channel is exported a pwmX directory will be created in the
+pwmchipN directory it is associated with, where X is the number of the
+channel that was exported. The following properties will then be available:
+
+period - The total period of the PWM signal (read/write).
+ Value is in nanoseconds and is the sum of the active and inactive
+ time of the PWM.
+
+duty_cycle - The active time of the PWM signal (read/write).
+ Value is in nanoseconds and must be less than the period.
+
+polarity - Changes the polarity of the PWM signal (read/write).
+ Writes to this property only work if the PWM chip supports changing
+ the polarity. The polarity can only be changed if the PWM is not
+ enabled. Value is the string "normal" or "inversed".
+
+enable - Enable/disable the PWM signal (read/write).
+ 0 - disabled
+ 1 - enabled
+
Implementing a PWM driver
-------------------------
@@ -57,7 +94,7 @@ for new drivers to use the generic PWM framework.
A new PWM controller/chip can be added using pwmchip_add() and removed
again with pwmchip_remove(). pwmchip_add() takes a filled in struct
pwm_chip as argument which provides a description of the PWM chip, the
-number of PWM devices provider by the chip and the chip-specific
+number of PWM devices provided by the chip and the chip-specific
implementation of the supported PWM operations to the framework.
Locking