From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Turquette Subject: Re: [PATCH 1/2] clk: of: helper for determining flags properties Date: Wed, 14 May 2014 21:47:28 -0700 Message-ID: <20140515044728.19795.43070@quantum> References: <1399982253-21079-1-git-send-email-gabriel.fernandez@linaro.org> <1399982253-21079-2-git-send-email-gabriel.fernandez@linaro.org> <20140513122054.GA2419@e106331-lin.cambridge.arm.com> <5372363B.4080608@gmail.com> <20140513204924.5943.24086@quantum> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Gabriel Fernandez Cc: Mark Rutland , "devicetree@vger.kernel.org" , "kernel@stlinux.com" , Pawel Moll , "ijc+devicetree@hellion.org.uk" , "rdunlap@infradead.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "robh+dt@kernel.org" , "galak@codeaurora.org" , Lee Jones , Gabriel FERNANDEZ , "linux-arm-kernel@lists.infradead.org" , Sebastian Hesselbarth List-Id: devicetree@vger.kernel.org Quoting Gabriel Fernandez (2014-05-14 00:53:58) > Hi, > > On 13 May 2014 22:49, Mike Turquette wrote: > > Quoting Sebastian Hesselbarth (2014-05-13 08:11:55) > >> On 05/13/2014 02:20 PM, Mark Rutland wrote: > >> > On Tue, May 13, 2014 at 12:57:32PM +0100, Gabriel FERNANDEZ wrote: > >> >> The patch provides a helper to get flags properties of > >> >> a clock node. > >> >> > >> >> Signed-off-by: Gabriel Fernandez > >> >> --- > >> >> drivers/clk/clk.c | 11 +++++++++++ > >> >> include/linux/clk-provider.h | 6 ++++++ > >> >> 2 files changed, 17 insertions(+) > >> >> > >> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > >> >> index 4d56220..cae8985 100644 > >> >> --- a/drivers/clk/clk.c > >> >> +++ b/drivers/clk/clk.c > >> >> @@ -2528,6 +2528,17 @@ const char *of_clk_get_parent_name(struct device_node *np, int index) > >> >> } > >> >> EXPORT_SYMBOL_GPL(of_clk_get_parent_name); > >> >> > >> >> +unsigned long of_clk_get_flags(struct device_node *np) > >> >> +{ > >> >> + unsigned long flags = 0; > >> >> + > >> >> + if (of_property_read_bool(np, "set-rate-parent")) > >> >> + flags |= CLK_SET_RATE_PARENT; > >> > > >> > NAK. > >> > > >> > This is _not_ a hardware property. This flag describes internals of the > >> > Linux clock framework, and is thus not suitable for DT. > >> > >> Mark, > >> > >> while I agree above property is not a hardware property, it is at least > >> some kind of use-case property. If not by DT, we will have to allow some > >> way to describe master-slave relationships between clocks in a driver > >> independent way. > > > > I agree with Mark. > > > > Generally this stuff belongs in a clock driver. Of course there are the > > integration issues you pointed out. More on that below. > > > > As an aside, CLK_SET_RATE_PARENT is a headache, since propagation of the > > operation up to the parent clock really should be the default behavior > > for .set_rate (and in fact this is the case for the new-ish > > .determine_rate op). Some history on those decisions can be found at [1] > > and [2]. > > > > > My issue is exactly the same as Marc, it's for solve some case with > PCM and HDMI clocks. > > >> > >> > You've also failed to document the property. > >> > > >> > What are you trying to achieve here, and why do you think this is the > >> > best way of achieving that? > >> > >> I cannot tell from the commit msgs, but consider clk-si5351 which is a > >> driver for an external programmable clock with N PLLs and M outputs. Now > >> connect a video clock consumer and an audio clock consumer to two > >> different outputs and those to one PLL (as you want audio clock derived > >> from video clock, typical HDMI scenario). > >> > >> Now, there should be a way to tell the generic driver which outputs are > >> allowed to change the PLLs rate and which don't. Otherwise, the clock > >> chip would be pretty useless as e.g. your audio clock consumer will > >> overwrite the rate the video clock consumer has chosen. > > > > This is really a job for the "coordinated clock rate changes" that are > > currently in development. These specify clock sub-tree snapshots of > > parent and rate configurations that are predefined. These combinations > > can be specified in DT. That helps a lot with clock configurations that > > change per board, or for cases where many combinations of parents and > > dividers can yield the same output rate, but only a subset of those were > > validated by the silicon validation team or had proper timing closure so > > we don't want to rely on the "walk up the tree" algorithm. > > > > Regards, > > Mike > > Ok i think this work will be the best solutions for my issue. > > Where i can find some threads about that ? Hi Gabriel, Glad that it sounds interesting to you. There isn't a dedicated discussion thread but I did outline some of the ideas earlier today on a separate thread[1]. It's being actively worked on and maybe an RFC can hit the list soon. Regards, Mike [1] http://www.spinics.net/lists/arm-kernel/msg331462.html > > Thanks a lot. > > Best Regards. > > Gabriel.