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Fri, 19 Jul 2019 01:19:26 +0000 (GMT) Subject: Re: [PATCH v4 11/24] PM / devfreq: tegra30: Add debug messages To: Dmitry Osipenko Cc: Thierry Reding , MyungJoo Ham , Kyungmin Park , Jonathan Hunter , Tomeu Vizoso , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org From: Chanwoo Choi Organization: Samsung Electronics Message-ID: Date: Fri, 19 Jul 2019 10:22:37 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190719041357.0a80a2dc@dimatab> Content-Language: en-US Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA02Se2xLcRTH/Xpvb1uUnzI7Gma7Dckq23pXnUts8YpVmEwkgqi5Wa9u1t42 vZ2MSbwfW2yIP8RlNjbmMTYzsi1kNmQm8SYRy2i8HzOqHlsQ2l5i/33O8/s753fUhO4MpVfn Cj7eK3BOmhpIXrgSn5RQrmdspr6nBvZU4Dlit0hHSPbmpm4Ve7/5IMUGS64ituiLRLGdG49T bF/zIZItPX2PmqaxNnZVIWuT1KWylmzuoaylDSeRNVgfk6lcmjc1h+fsvDeWF7Ld9lzBkUrP XZg1M8uSYmISmMnsJDpW4Fx8Kj1rXmbC7Fxn6EF07GrOmR9yZXKiSCelTfW68318bI5b9KXS vMfu9Ez2JIqcS8wXHInZbtcUxmRKtoQSV+Tl/Apgzy1DQeBCjXIDqhldjDRqwBNBelKmKEYD 1TrciCAYeP/X+Iygt+WMUja+IdjUWkkWI3Wk5FPTBNl/CcGr1xWkbHxEUF3aSob7DsfpULf7 uCLMI/B4qL72M9KJwGcV0F5XEwlQ2Agtbx5RYR6K4+Bh73MUZi1Og0fPNqrCTOJx4P90Wxnm KLwYPvuvKOWcYdCx/0VETIMTof51ZcRP4Gh4/KJcIfNY2Hz+ABEWBvybgmO1pwh5hFnQfcIm L2A4vGtvUMmsh2DPJUrmQjjRcZWSa3cgaGi5o5QDZmg5ulcR7kPgeKhtTpLdcdD0owzJukOg 5+tOpSylhR3bdHKKAe77uxQyj4LK7UXUbkRL/aaR+k0g9ZtA+i9WgciTaCTvEV0OXmQ8yf0/ ux5FbtWY0oiO3JrXhrAa0YO1vatMNp2SWy2ucbUhUBP0CG3n2ySbTmvn1qzlve4sb76TF9uQ JbTsPYQ+KtsdunzBl8VYks1mMzuRSbEwDB2tPfQz3qbDDs7H5/G8h/f+q1OoNfoNaPld86Dp +4pe5kbFF0QXlmekZWcstaxfX3e5SrBu7SwjYto/SMmGi27XvqIlF1uXGbe0N/lrzOf4G4a3 txfZm990rMyLOzzKpekrGV3hWBc0rjivRdcCwq5a/6Tu712mOSljHg9VFcaUVJcvum6YNr+g rlHlZAak7/pyVPPg44IZNpoUczjGSHhF7g+QS6K0wQMAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprJIsWRmVeSWpSXmKPExsWy7bCSnO58KcNYg6Wr2S1Wf3zMaNEyaxGL xdmmN+wWl3fNYbP43HuE0aLzyyw2i9uNK9gsfu6ax2LRt/YSmwOnx467Sxg9ds66y+7R2/yO zaNvyypGj8+b5AJYo7hsUlJzMstSi/TtErgy/n4UKDinXPFx2xrWBsY1Ml2MHBwSAiYSH3Zq dzFycQgJ7GaU2LRuFmMXIydQXFJi2sWjzBA1whKHDxdD1LxllJh97A87SI2wgLvEhgkrmEBs EQE1ieVH/7CCFDELbGaSOHtqNRtEx11miSUHe8Cq2AS0JPa/uMEGYvMLKEpc/fEYbBuvgJ3E jUeNYFNZBFQlHnw4zwpiiwpESBzeMQuqRlDi5MwnLCA2p4CexKbni8FqmAXUJf7Mu8QMYYtL 3HoynwnClpdo3jqbeQKj8Cwk7bOQtMxC0jILScsCRpZVjJKpBcW56bnFhgWGeanlesWJucWl eel6yfm5mxjBEaaluYPx8pL4Q4wCHIxKPLwBuQaxQqyJZcWVuYcYJTiYlUR4b7/UjxXiTUms rEotyo8vKs1JLT7EKM3BoiTO+zTvWKSQQHpiSWp2ampBahFMlomDU6qBUbwxVeq7LntL74Vl QsvXq5r+8e1zzt636HtV4wGOo5VzynKcNhsv0nvy7OpEtw9PVUMc9d60WX1Q8eg6Xe6b+SR+ exh7dD//XJO7citZZt2sXnGEtdF8TpnbcaYDzX2i56Rzw1oluIKC/4t5srBEKWjPvrLT8/E5 UzPbnEi545MZ8yd4pP9UYinOSDTUYi4qTgQAoUyDVawCAAA= X-CMS-MailID: 20190719011927epcas1p1a5bd6d20763dd44bffe8472e037a2b47 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20190707223640epcas4p15337f40466342832b731ad6a53be946e References: <20190707223303.6755-1-digetx@gmail.com> <20190707223303.6755-12-digetx@gmail.com> <53cd0ba5-f814-cd9b-19c5-1d42717ca58c@gmail.com> <922c9178-71de-46ad-eafd-805af461bedb@samsung.com> <20190719041357.0a80a2dc@dimatab> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19. 7. 19. 오전 10:13, Dmitry Osipenko wrote: > В Thu, 18 Jul 2019 18:07:05 +0900 > Chanwoo Choi пишет: > >> On 19. 7. 18. 오전 12:46, Dmitry Osipenko wrote: >>> 17.07.2019 9:45, Chanwoo Choi пишет: >>>> On 19. 7. 16. 오후 10:26, Dmitry Osipenko wrote: >>>>> 16.07.2019 15:23, Chanwoo Choi пишет: >>>>>> Hi Dmitry, >>>>>> >>>>>> Usually, the kernel log print for all users >>>>>> such as changing the frequency, fail or success. >>>>>> >>>>>> But, if the log just show the register dump, >>>>>> it is not useful for all users. It is just used >>>>>> for only specific developer. >>>>>> >>>>>> I recommend that you better to add more exception handling >>>>>> code on many points instead of just showing the register dump. >>>>> >>>>> The debug messages are not users, but for developers. Yes, I >>>>> primarily made the debugging to be useful for myself and will be >>>>> happy to change the way debugging is done if there will be any >>>>> other active developer for this driver. The registers dump is >>>>> more than enough in order to understand what's going on, I don't >>>>> see any real need to change anything here for now. >>>> >>>> Basically, we have to develop code and add the log for anyone. >>>> As you commented, even if there are no other developer, we never >>>> guarantee this assumption forever. And also, if added debug message >>>> for only you, you can add them when testing it temporarily. >>>> >>>> If you want to add the just register dump log for you, >>>> I can't agree. Once again, I hope that anyone understand >>>> the meaning of debug message as much possible as. >>>> >>> >>> The registers dump should be good for everyone because it's a >>> self-explanatory information for anyone who is familiar with the >>> hardware. I don't think there is a need for anything else than what >>> is proposed in this patch, at least for now. I also simply don't >>> see any other better way to debug the state of this particular >>> hardware, again this logging is for the driver developers and not >>> for users. >>> >>> Initially, I was temporarily adding the debug messages. Now they are >>> pretty much mandatory for verifying that driver is working >>> properly. And of course the debugging messages got into the shape >>> of this patch after several iterations of refinements. So again, I >>> suppose that this should be good enough for everyone who is >>> familiar with the hardware. And of course I'm open to the >>> constructive suggestions, the debugging aid is not an ABI and could >>> be changed/improved at any time. >>> >>> You're suggesting to break down the debugging into several smaller >>> pieces, but I'm finding that as not a constructive suggestion >>> because the information about the full hardware state is actually >>> necessary for the productive debugging. >>> >>> >> >> Sorry for that as I saie, I cannot agree this patch. In my case, >> I don't understand what is meaning of register dump of this patch. >> I knew that just register dump are useful for real developer. > > It's not only a registers dump, as you may see there is also a dump of > other properties like boosting value, OPPs selection and etc. > > It looks to me that you're also missing important detail that debug > messages are compiled out unless DEBUG is defined for the drivers > build. So in order to get the debug message a user shall explicitly add > #define DEBUG macro to the code or enable debug messages globally in > the kernel's config. There is also an option for dynamic debug messages > in the kernel, but it doesn't matter now because all these messages are > turned into tracepoints later in the patch #17. Right. But, this patch could not the split up between register dump and others. As I said repeatly, I hope to add the log that anyone can understand. > >> If you want to show the register dump, you better to add some feature >> with debugfs for devfreq framework in order to read the register dump. >> As I knew, sound framework (alsa) has the similar feature for checking >> the register dump. >> > > The intent was to have an option for dynamic debugging of the driver and > initially debug messages were good enough, but then it became not enough > and hence the debug messages were turned into tracepoints in the patch > #17. Would it be acceptable to squash this patch and #17? > > > -- Best Regards, Chanwoo Choi Samsung Electronics