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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH v2 22/65] clk: davinci: da8xx-cfgchip: Add a determine_rate hook Content-Language: en-US To: Maxime Ripard , Stephen Boyd , Maxime Coquelin , Chen-Yu Tsai , Daniel Vetter , Nicolas Ferre , Thierry Reding , Jaroslav Kysela , Shawn Guo , Fabio Estevam , Ulf Hansson , Claudiu Beznea , Michael Turquette , Dinh Nguyen , Paul Cercueil , Chunyan Zhang , Manivannan Sadhasivam , =?UTF-8?Q?Andreas_F=c3=a4rber?= , Jonathan Hunter , Abel Vesa , Charles Keepax , Alessandro Zummo , Peter De Schrijver , Orson Zhai , Alexandre Torgue , Prashant Gaikwad , Liam Girdwood , Alexandre Belloni , Samuel Holland , Matthias Brugger , Richard Fitzgerald , Vinod Koul , NXP Linux Team , Sekhar Nori , Kishon Vijay Abraham I , Linus Walleij , Takashi Iwai , David Airlie , Luca Ceresoli , Jernej Skrabec , Pengutronix Kernel Team , Baolin Wang , Sascha Hauer , Mark Brown , Max Filippov , Geert Uytterhoeven References: <20221018-clk-range-checks-fixes-v2-0-f6736dec138e@cerno.tech> <20221018-clk-range-checks-fixes-v2-22-f6736dec138e@cerno.tech> From: David Lechner In-Reply-To: <20221018-clk-range-checks-fixes-v2-22-f6736dec138e@cerno.tech> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - vern.gendns.com X-AntiAbuse: Original Domain - alsa-project.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lechnology.com X-Get-Message-Sender-Via: vern.gendns.com: authenticated_id: davidmain+lechnology.com/only user confirmed/virtual account not confirmed X-Authenticated-Sender: vern.gendns.com: davidmain@lechnology.com X-Source: X-Source-Args: X-Source-Dir: X-Mailman-Approved-At: Sat, 05 Nov 2022 08:03:30 +0100 Cc: linux-rtc@vger.kernel.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, patches@opensource.cirrus.com, linux-actions@lists.infradead.org, linux-mips@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-clk@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-tegra@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-phy@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, AngeloGioacchino Del Regno X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On 11/4/22 8:17 AM, Maxime Ripard wrote: > The Davinci DA8xxx cfgchip "clk48" clock implements a mux with a > set_parent hook, but doesn't provide a determine_rate implementation. > > This is a bit odd, since set_parent() is there to, as its name implies, > change the parent of a clock. However, the most likely candidate to > trigger that parent change is a call to clk_set_rate(), with > determine_rate() figuring out which parent is the best suited for a > given rate. > > The other trigger would be a call to clk_set_parent(), but it's far less > used, and it doesn't look like there's any obvious user for that clock. > > So, the set_parent hook is effectively unused, possibly because of an > oversight. However, it could also be an explicit decision by the > original author to avoid any reparenting but through an explicit call to > clk_set_parent(). > > The latter case would be equivalent to setting the flag > CLK_SET_RATE_NO_REPARENT, together with setting our determine_rate hook > to __clk_mux_determine_rate(). Indeed, if no determine_rate > implementation is provided, clk_round_rate() (through > clk_core_round_rate_nolock()) will call itself on the parent if > CLK_SET_RATE_PARENT is set, and will not change the clock rate > otherwise. __clk_mux_determine_rate() has the exact same behavior when > CLK_SET_RATE_NO_REPARENT is set. > > And if it was an oversight, then we are at least explicit about our > behavior now and it can be further refined down the line. The parent is defined in the device tree and is not expected to change at runtime, so if I am understanding the patch correctly, setting the CLK_SET_RATE_NO_REPARENT flag seems correct. > > Signed-off-by: Maxime Ripard > --- > drivers/clk/davinci/da8xx-cfgchip.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/clk/davinci/da8xx-cfgchip.c b/drivers/clk/davinci/da8xx-cfgchip.c > index c04276bc4051..4c1cc59bba53 100644 > --- a/drivers/clk/davinci/da8xx-cfgchip.c > +++ b/drivers/clk/davinci/da8xx-cfgchip.c > @@ -565,6 +565,7 @@ static u8 da8xx_usb1_clk48_get_parent(struct clk_hw *hw) > } > > static const struct clk_ops da8xx_usb1_clk48_ops = { > + .determine_rate = __clk_mux_determine_rate, > .set_parent = da8xx_usb1_clk48_set_parent, > .get_parent = da8xx_usb1_clk48_get_parent, > }; > @@ -589,6 +590,7 @@ da8xx_cfgchip_register_usb1_clk48(struct device *dev, > > init.name = "usb1_clk48"; > init.ops = &da8xx_usb1_clk48_ops; > + init.flags = CLK_SET_RATE_NO_REPARENT; > init.parent_names = parent_names; > init.num_parents = 2; > >