Hi Paul, On 03/02/2016 10:22 AM, Franklin S Cooper Jr. wrote: > Hi Paul > > On 03/01/2016 02:50 PM, Tony Lindgren wrote: >> * Paul Walmsley <paul@xxxxxxxxx> [160301 10:59]: >>> On Tue, 1 Mar 2016, Tony Lindgren wrote: >>> >>>> * Franklin S Cooper Jr <fcooper@xxxxxx> [160225 14:37]: >>>>> From: Vignesh R <vigneshr@xxxxxx> >>>>> >>>>> Add hwmod entries for the PWMSS on DRA7. >>>>> >>>>> Set l4_root_clk_div as the main_clk of PWMSS. It is fixed-factored clock >>>>> equal to L4PER2_L3_GICLK/2(l3_iclk_div/2). >>>>> As per AM57x TRM SPRUHZ6[1], October 2014, Section 29.1.3 Table 29-4, >>>>> clock source to PWMSS is L4PER2_L3_GICLK. But it is actually >>>>> L4PER2_L3_GICLK/2. The TRM does not show the division by 2. >>>>> >>>>> [1] www.ti.com/lit/ug/spruhz6/spruhz6.pdf >>>> Looks OK to me, assuming Paul will pick this one or ack it. >>> Well I've already sent comments on it, it doesn't look quite ready for me >>> yet. I would hold off on the whole series because the hwmod comments also >>> impact the DT files. >> OK will drop the dt related patches then. > Sorry you previously asked this question about why hwmod is > used for eCap, ePWM and eQEP before and it wasn't addressed. > I'll take a look at this and I will get back to you. 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. 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? 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. > >> Regards, >> >> Tony -- 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
