From mboxrd@z Thu Jan 1 00:00:00 1970 From: Krzysztof Kozlowski Subject: Re: [PATCH v5 05/14] clk: Add generic driver for Maxim PMIC clocks Date: Wed, 02 Jul 2014 12:19:57 +0200 Message-ID: <1404296397.12439.2.camel@AMDC1943> References: <1403806546-31122-1-git-send-email-javier.martinez@collabora.co.uk> <1403806546-31122-6-git-send-email-javier.martinez@collabora.co.uk> <20140701172616.32686.44374@quantum> <53B3DB49.6020604@collabora.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-reply-to: <53B3DB49.6020604@collabora.co.uk> Sender: linux-samsung-soc-owner@vger.kernel.org To: Javier Martinez Canillas Cc: Mike Turquette , Yadwinder Singh Brar , Lee Jones , Samuel Ortiz , Mark Brown , Liam Girdwood , Alessandro Zummo , Kukjin Kim , Doug Anderson , Olof Johansson , Sjoerd Simons , Daniel Stone , Tomeu Vizoso , "linux-arm-kernel@lists.infradead.org" , devicetree , linux-samsung-soc , linux-kernel List-Id: devicetree@vger.kernel.org On =C5=9Bro, 2014-07-02 at 12:13 +0200, Javier Martinez Canillas wrote: > Hello Mike, >=20 > On 07/01/2014 07:26 PM, Mike Turquette wrote: > > Quoting Yadwinder Singh Brar (2014-06-29 21:01:36) > >> Hi Javier, > >>=20 > >> On Thu, Jun 26, 2014 at 11:45 PM, Javier Martinez Canillas > >> wrote: > >> > Maxim Integrated Power Management ICs are very similar with > >> > regard to their clock outputs. Most of the clock drivers for > >> > these chips are duplicating code and are simpler enough that > >> > can be converted to use a generic driver to consolidate code > >> > and avoid duplication. > >> > > >> > Signed-off-by: Javier Martinez Canillas > >> > Reviewed-by: Krzysztof Kozlowski > >> > --- > >> > > >> > Changes since v4: > >> > - Return recalc 0 if clock isn't enabled in Suggested by Yadwin= der Singh Brar. > >> > > >>=20 > >> It seems you didn't implement or posted same patch again :) . > >>=20 > >> > Changes since v3: > >> > - Add current copyright information. Suggested by Krzysztof Koz= lowski > >> > - Do a single allocation for struct max_gen_clk. Suggested by K= rzysztof Kozlowski > >> > - Add EXPORT_SYMBOL() for exported symbols. Suggested by Krzysz= tof Kozlowski > >> > > >> > drivers/clk/Kconfig | 3 + > >> > drivers/clk/Makefile | 1 + > >> > drivers/clk/clk-max-gen.c | 195 +++++++++++++++++++++++++++++++= +++++++++++++++ > >> > drivers/clk/clk-max-gen.h | 32 ++++++++ > >> > 4 files changed, 231 insertions(+) > >> > create mode 100644 drivers/clk/clk-max-gen.c > >> > create mode 100644 drivers/clk/clk-max-gen.h > >> > > >>=20 > >> [ .. ] > >>=20 > >> > + > >> > +static unsigned long max_gen_recalc_rate(struct clk_hw *hw, > >> > + unsigned long parent_ra= te) > >> > +{ > >> > + return 32768; > >> > +} > >>=20 > >> Its still same here. > >=20 > > Changing this would be a new behavior. I do not know of any other c= lock > > drivers that conditionally returns a rate of 0 based on whether or = not > > the clock is gated. > >=20 >=20 > After Yadwinder feedback I searched for clock drivers that returned 0= when the > clock was not enabled/prepared and found for example drivers/clk/clk-= s2mps11.c: >=20 >=20 > static unsigned long s2mps11_clk_recalc_rate(struct clk_hw *hw, > unsigned long parent_rat= e) > { > struct s2mps11_clk *s2mps11 =3D to_s2mps11_clk(hw); > if (s2mps11->enabled) > return 32768; > else > return 0; > } >=20 > > It is also buggy since calls to clk_enable and clk_disable do not i= nvoke > > .recalc_rate, so the rate of your clock would not be updated from t= he > > framework's perspective until some later point where you call > > clk_set_rate or something. > > >=20 > s2ps11->enabled is set in the driver's clk_ops .prepare and .unprepar= e function > handlers and calls to clk_prepare and clk_unprepare also don't seems = to invoke > .recalc_rate so I guess that driver is wrong as well and should just = return the > clock rate unconditionally? The s2mps11 may be not a best example for proper clock driver :). Karol Wrona already sent a patch for s2mps11: https://lkml.org/lkml/2014/7/1/389 Best regards, Krzysztof >=20 > > If your driver needs to know whether or not the clock is enabled th= en we > > could introduce a new bool clk_is_enabled(struct clk *clk); to clk.= h, > > but I'd rather not do that. Instead if a driver needs a clock then = it > > calls clk_enable on it without any knowledge about the internal sta= te of > > the clock enable_count. > >=20 > > Regards, > > Mike > > >=20 > Thanks a lot for the explanation, I'll revert that change then and re= turn the > clock rate unconditionally on the next version of the patch-set. >=20 > Best regards, > Javier