From: Russell King - ARM Linux <firstname.lastname@example.org> To: Stephen Boyd <email@example.com> Cc: Dmitry Torokhov <firstname.lastname@example.org>, Guenter Roeck <email@example.com>, Michael Turquette <firstname.lastname@example.org>, Viresh Kumar <email@example.com>, Andy Shevchenko <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org Subject: Re: [PATCH v3] clk: add more managed APIs Date: Tue, 14 Feb 2017 20:01:13 +0000 [thread overview] Message-ID: <20170214200113.GA27312@n2100.armlinux.org.uk> (raw) In-Reply-To: <20170214194408.GW25384@codeaurora.org> On Tue, Feb 14, 2017 at 11:44:08AM -0800, Stephen Boyd wrote: > I'd prefer we didn't do this. Instead, make clk_put() drop any > prepare or enables that were done via that clk pointer. Mike > started to do this before, but we have some code that assumes > it can do: > > clk = clk_get(...) > clk_prepare_enable(clk) > clk_put(clk) > > and have the clk stay on. Those would need to be changed. Yes, I've seen from time to time code that plays this game over the years. However, from my simple grepping, it seems that we only have a small number of cases: arch/mips/alchemy/devboards/db1200.c: clk_prepare_enable(c); arch/mips/alchemy/devboards/db1200.c- clk_put(c); arch/mips/alchemy/devboards/db1300.c: clk_prepare_enable(c); arch/mips/alchemy/devboards/db1300.c- clk_put(c); arch/mips/alchemy/devboards/db1550.c: clk_prepare_enable(c); arch/mips/alchemy/devboards/db1550.c- clk_put(c); drivers/base/power/clock_ops.c: clk_prepare_enable(clk); drivers/base/power/clock_ops.c- clk_put(clk); drivers/mtd/nand/orion_nand.c: clk_prepare_enable(clk); drivers/mtd/nand/orion_nand.c- clk_put(clk); I've always hated that - and it goes against the API: * Note: drivers must ensure that all clk_enable calls made on this * clock source are balanced by clk_disable calls prior to calling * this function. (That comment should have been updated when clk_prepare() & clk_unprepare() was added to include balancing those.) So really, all the cases above are buggy. However, the statement in the API doesn't give permission for what you're suggesting! The suggestion requires that we also cast in stone that every "struct clk" which is handed out from clk_get() becomes unique _everywhere_, because that's the only way to really track the prepare/enable state on a per- clk_get() basis, so we can properly clean up at clk_put(). However, I think we still have some non-CCF clock API implementations around, which hand out shared "struct clk"s. Changing this requirement will impact those, since they would need to be updated before the change could be made. So, although it would be a nice change to make (which would rule out the abuse) I don't think it's one that could be practically made at this stage without (a) fixing all instances like those quoted above and (b) converting all non-CCF implementations to either CCF or making them hand out unique struct clk's. (I do have patches which converts sa11x0 to CCF... which would be one less non-CCF implementation.) -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
prev parent reply other threads:[~2017-02-14 20:01 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-01-28 18:40 [PATCH] " Dmitry Torokhov 2017-01-28 19:03 ` Russell King - ARM Linux 2017-01-28 19:22 ` Dmitry Torokhov 2017-01-28 21:44 ` Guenter Roeck 2017-01-28 23:39 ` Russell King - ARM Linux 2017-01-29 16:00 ` Guenter Roeck 2017-01-29 18:07 ` [PATCH v2] " Dmitry Torokhov 2017-01-29 18:31 ` Guenter Roeck 2017-01-30 18:55 ` Stephen Boyd 2017-01-30 19:22 ` Guenter Roeck 2017-01-30 21:42 ` Russell King - ARM Linux 2017-01-30 21:58 ` Dmitry Torokhov 2017-01-30 22:25 ` Russell King - ARM Linux 2017-01-30 22:51 ` Guenter Roeck 2017-01-31 8:43 ` Geert Uytterhoeven 2017-01-31 0:59 ` Dmitry Torokhov 2017-01-31 17:20 ` Guenter Roeck 2017-01-31 18:26 ` Dmitry Torokhov 2017-01-31 19:34 ` Guenter Roeck 2017-01-31 0:57 ` [PATCH v3] " Dmitry Torokhov 2017-02-07 3:51 ` Dmitry Torokhov 2017-02-14 19:44 ` Stephen Boyd 2017-02-14 19:55 ` Dmitry Torokhov 2017-02-14 20:31 ` Guenter Roeck 2017-02-14 20:01 ` Russell King - ARM Linux [this message]
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