From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [PATCH] mfd: twl6040: Optional clk32k clock handling Date: Mon, 28 Apr 2014 13:50:52 +0100 Message-ID: <20140428125052.GK21279@lee--X1> References: <1396522482-32036-1-git-send-email-peter.ujfalusi@ti.com> <20140428103629.GI21279@lee--X1> <535E319A.9050104@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <535E319A.9050104@ti.com> Sender: linux-doc-owner@vger.kernel.org To: Peter Ujfalusi Cc: sameo@linux.intel.com, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: devicetree@vger.kernel.org On Mon, 28 Apr 2014, Peter Ujfalusi wrote: > On 04/28/2014 01:36 PM, Lee Jones wrote: > >> In certain boards the source for the clk32k clock can be gated. In= these > >> boards the clk32k clock can be provided to the driver and it is go= ing to be > >> enabled/disabled when it is needed. > >> If the clk32k clock is not provided the driver will assume that it= is always > >> running. > >> > >> Signed-off-by: Peter Ujfalusi > >> --- > >> Documentation/devicetree/bindings/mfd/twl6040.txt | 2 ++ > >> drivers/mfd/twl6040.c | 10 ++++++++++ > >> include/linux/mfd/twl6040.h | 2 ++ > >> 3 files changed, 14 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/mfd/twl6040.txt b/D= ocumentation/devicetree/bindings/mfd/twl6040.txt > >> index 0f5dd709d752..a41157b5d930 100644 > >> --- a/Documentation/devicetree/bindings/mfd/twl6040.txt > >> +++ b/Documentation/devicetree/bindings/mfd/twl6040.txt > >> @@ -19,6 +19,8 @@ Required properties: > >> =20 > >> Optional properties, nodes: > >> - enable-active-high: To power on the twl6040 during boot. > >> +- clocks: phandle to the clk32k clock provider > >> +- clock-names: Must be "clk32k" > >> =20 > >> Vibra functionality > >> Required properties: > >> diff --git a/drivers/mfd/twl6040.c b/drivers/mfd/twl6040.c > >> index 2e6504a8e1e3..12b314ea48dc 100644 > >> --- a/drivers/mfd/twl6040.c > >> +++ b/drivers/mfd/twl6040.c > >> @@ -291,6 +291,8 @@ int twl6040_power(struct twl6040 *twl6040, int= on) > >> if (twl6040->power_count++) > >> goto out; > >> =20 > >> + clk_prepare_enable(twl6040->clk32k); > >> + > >> /* Allow writes to the chip */ > >> regcache_cache_only(twl6040->regmap, false); > >> =20 > >> @@ -346,6 +348,8 @@ int twl6040_power(struct twl6040 *twl6040, int= on) > >> =20 > >> twl6040->sysclk =3D 0; > >> twl6040->mclk =3D 0; > >> + > >> + clk_disable_unprepare(twl6040->clk32k); > >> } > >> =20 > >> out: > >> @@ -644,6 +648,12 @@ static int twl6040_probe(struct i2c_client *c= lient, > >> =20 > >> i2c_set_clientdata(client, twl6040); > >> =20 > >> + twl6040->clk32k =3D devm_clk_get(&client->dev, "clk32k"); > >> + if (IS_ERR(twl6040->clk32k)) { > >> + dev_info(&client->dev, "clk32k is not handled\n"); > >> + twl6040->clk32k =3D NULL; > >=20 > > So what happens if you pass a NULL clk reference to clk_prepare_ena= ble()? >=20 > We have checks for !clk in all cases within the clk_* API. If we pass= NULL, > nothing will happen and from the calling driver point of view it will= look > like a success. > AFAIK this is the way to handle non esential/optional clocks without = if()s in > the driver code around the clock handling. Okay, so long as those checks are there, we're all good. --=20 Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org =E2=94=82 Open source software for ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog