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[109.252.193.159]) by smtp.googlemail.com with ESMTPSA id r66sm835570lff.265.2020.11.08.21.29.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 08 Nov 2020 21:29:51 -0800 (PST) Subject: Re: [PATCH 2/2] opp: Don't create an OPP table from dev_pm_opp_get_opp_table() To: Viresh Kumar Cc: "Rafael J. Wysocki" , Kevin Hilman , Ulf Hansson , Len Brown , Pavel Machek , Greg Kroah-Hartman , Viresh Kumar , Nishanth Menon , Stephen Boyd , linux-pm@vger.kernel.org, Vincent Guittot , linux-kernel@vger.kernel.org References: <684ff01900180c0a40ec307dacc673b24eab593b.1604643714.git.viresh.kumar@linaro.org> <1012a98950355bd5a52424668050a17c3430cbe0.1604643714.git.viresh.kumar@linaro.org> <20201109043457.xf55kufhjjz2fvct@vireshk-i7> <20201109045740.y5kpd6tjscoqxhi5@vireshk-i7> From: Dmitry Osipenko Message-ID: <7a0a904d-8ee2-d1d6-509c-950bb408e0c5@gmail.com> Date: Mon, 9 Nov 2020 08:29:50 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201109045740.y5kpd6tjscoqxhi5@vireshk-i7> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 09.11.2020 07:57, Viresh Kumar пишет: > On 09-11-20, 07:41, Dmitry Osipenko wrote: >> 09.11.2020 07:34, Viresh Kumar пишет: >>> On 06-11-20, 16:18, Dmitry Osipenko wrote: >>>> 06.11.2020 09:24, Viresh Kumar пишет: >>>>> It has been found that some users (like cpufreq-dt and others on LKML) >>>>> have abused the helper dev_pm_opp_get_opp_table() to create the OPP >>>>> table instead of just finding it, which is the wrong thing to do. This >>>>> routine was meant for OPP core's internal working and exposed the whole >>>>> functionality by mistake. >>>>> >>>>> Change the scope of dev_pm_opp_get_opp_table() to only finding the >>>>> table. The internal helpers _opp_get_opp_table*() are thus renamed to >>>>> _add_opp_table*(), dev_pm_opp_get_opp_table_indexed() is removed (as we >>>>> don't need the index field for finding the OPP table) and so the only >>>>> user, genpd, is updated. >>>>> >>>>> Note that the prototype of _add_opp_table() was already left in opp.h by >>>>> mistake when it was removed earlier and so we weren't required to add it >>>>> now. >>>> >>>> Hello Viresh, >>>> >>>> It looks like this is not an entirely correct change because previously >>>> it was possible to get an empty opp_table in order to use it for the >>>> dev_pm_opp_set_rate(), which would fall back to clk_set_rate if table is >>>> empty. >>>> >>>> Now it's not possible to get an empty table and >>>> dev_pm_opp_of_add_table() would error out if OPPs are missing in a >>>> device-tree. Hence it's not possible to implement a fall back without >>>> abusing opp_set_regulators() or opp_set_supported_hw() for getting the >>>> empty table. Or am I missing something? >>> >>> For that case you were always required to call >>> dev_pm_opp_set_clkname(), otherwise how would the OPP core know which >>> clock to set ? And the same shall work now as well. >> >> Why _allocate_opp_table() grabs the first default clk of a device and >> assigns it to the created table? > > Right, it was there so everybody isn't required to call > dev_pm_opp_set_clkname() if they don't need to pass a connection id > while getting the clock. But for the case of supporting empty OPP > tables for cases where we just want dev_pm_opp_set_rate() to act as > clk_set_rate() (in order for the drivers to avoid supporting two > different ways of doing so), we do need that call to be made. > > We need to add the OPP table explicitly and what happened with > dev_pm_opp_get_opp_table() was accidental and not what I wanted. > > drivers/mmc/host/sdhci-msm.c has an example of how this is done. > Alright, thank you for the clarification.