From mboxrd@z Thu Jan 1 00:00:00 1970 From: swarren@wwwdotorg.org (Stephen Warren) Date: Fri, 23 Aug 2013 13:36:23 -0600 Subject: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM In-Reply-To: <20130823091052.GG3535@ulmo> References: <1377054462-6283-1-git-send-email-Li.Xiubo@freescale.com> <1377054462-6283-5-git-send-email-Li.Xiubo@freescale.com> <20130823091052.GG3535@ulmo> Message-ID: <5217B9B7.9080802@wwwdotorg.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 08/23/2013 03:10 AM, Thierry Reding wrote: > On Wed, Aug 21, 2013 at 11:07:42AM +0800, Xiubo Li wrote: >> Signed-off-by: Xiubo Li --- >> .../devicetree/bindings/pwm/fsl-ftm-pwm.txt | 52 >> ++++++++++++++++++++++ 1 file changed, 52 insertions(+) create >> mode 100644 >> Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt >> diff --git >> a/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt >> b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt >> +Required properties: +- compatible: should be >> "fsl,vf610-ftm-pwm" +- reg: physical base address and length of >> the controller's registers +- #pwm-cells: Should be 3. Number of >> cells being used to specify PWM property. + First cell specifies >> the per-chip channel index of the PWM to use, the + second cell >> is the period in nanoseconds and bit 0 in the third cell is + >> used to encode the polarity of PWM output. Set bit 0 of the third >> in PWM + specifier to 1 for inverse polarity & set to 0 for >> normal polarity. Lines 2..n of a property description should be indented so it's easier to see where each entry in the list starts. >> +- fsl,pwm-clk-ps: the ftm0 pwm clock's prescaler, divide-by >> 2^n(n = 0 ~ 7). +- fsl,pwm-cpwm: Center-Aligned PWM (CPWM) mode. >> +- fsl,pwm-number: the number of PWM devices, and is must equal >> to the number + of "fsl,pwm-channels". Isn't that value a static facet of the HW, and hence it can be determined solely from the compatible value? >> +- fsl,pwm-channels: the channels' order which is be used for pwm >> in ftm0 + module, and they must be one or some of 0 ~ 7, because >> the ftm0 only has + 8 channels can be used. Why is there a need to re-order the channels? Why not simply reference the actual physical channel IDs in client nodes? >> +- for very channel, the revlatived the pinctrl should be at >> least two state + {"enN", "dsN"}, which "en" means "enable", >> "ds" means "disable" and "N" + means the order of the channel. revlatived?? Why is there a need for pinctrl interaction at all? Is the "N" in these property names the index into fsl,pwm-channels, or the physical channel number in the controller HW, or something else? "dis" would be better than "ds", although "enable-chN", "disable-chN" would be even better. Note that it's not possible to enable multiple pinctrl states at once, so what happens when channel 0 is enabled, yet channel 1 is disabled, and you want to enable "en0" and "ds1" at the same time?