On Thu, 3 Mar 2016, Franklin S Cooper Jr. wrote: > So I looked into this more and verified that the eCAP and > ePWM doesn't have their own unique clock. The PWMSS receives > a clock L4PER2_L3_GICLK/2 which is passed through to its > sub-devices (ePWM, eCAP and eQEP). The PWMSS is responsible > for handling its clock internally while the subdevices have > no role in managing this clock. So this explains why we have > hwmod entries for PWMSS and why we are planning on removing > it from the various subdevices. It's not whether they have their own unique clock, but whether the submodules have OCP integration registers, speak the idle/standby protocols, have direct L3/L4 ports, etc. > Since ePWM, eCAP and eQEP are subdevices of PWMSS they > shouldn't have their own concept of their "own" clock. The > ePWM , eCAP and eQEP clocks are all shared and managed by > their parent PWMSS. Once the PWMSS is enabled and has its > clock running then ePWM, eCAP and eQEP from their main clock > perspective have everything they need. > > So my plan is to strip all references of clocks (including > hwmod entries) for ePWM, eCAP and eQEP. The devm_clk_get > calls made in the ePWM and eCAP will simply point to their > parent's dev (PWMSS). I did a couple of quick test using > this approach and it works. I have more testing to do but if > that checks out are you ok with the above approach? I don't know if that should be done or not. I haven't stared at the code yet, but based on your description, it sounds to me that it probably shouldn't be done. In any case, it's not what I meant... > Also I'm not sure how simple-bus fits in this picture. The > eCAP, eQEP and ePWM are all separate devices. The only thing > that they share is a single clock from their parent. So it > doesn't seem like the right approach. I'm basing this on the > info in this thread > https://www.mail-archive.com/linuxppc-dev@xxxxxxxxxxxxxxxx/msg27979.html > that talks about the usage of simple-bus. So if its outdated > or I"m misinterpreting it incorrectly please let me know. What I meant is that the ECAP*, EQEP*, EHRPWM* devices don't need to be registered through the hwmod code, due to the fact that they don't have the integration mentioned above. Instead, I think those three subdevices should be listed as child nodes of epwmss* in the DT. Looking at the DT data from Vignesh, it looks like he's already got ehrpwm1 as a child node of the epwmss1: + epwmss1: epwmss@48440000 { + compatible = "ti,dra7xx-pwmss", "ti,am33xx-pwmss"; + reg = <0x48440000 0x30>; + ti,hwmods = "epwmss1"; + #address-cells = <1>; + #size-cells = <1>; + status = "disabled"; + ranges = <0x48440100 0x48440100 0x80 /* ECAP */ + 0x48440180 0x48440180 0x80 /* EQEP */ + 0x48440200 0x48440200 0x80>; /* EHRPWM */ + + ehrpwm1: ehrpwm@48440200 { + compatible = "ti,dra7xx-ehrpwm", + "ti,am33xx-ehrpwm"; + #pwm-cells = <3>; + reg = <0x48440200 0x80>; + ti,hwmods = "ehrpwm1"; So, drop the above line, since the subdevices don't have corresponding hwmods any more. + status = "disabled"; + }; Then, here, you'd add nodes similar to ehrpwm1 for ecap1 and eqep1. I can't remember at the moment if adding "simple-bus" to the epwmss1 string would be sufficient to register the subdevices after the epwmss1 is probed. If so, maybe that's all you need. + }; Then repeat for epwmss0, epwmss2. - Paul -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
