Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932173AbaD1KrA (ORCPT ); Mon, 28 Apr 2014 06:47:00 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:39117 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932084AbaD1Kq5 (ORCPT ); Mon, 28 Apr 2014 06:46:57 -0400 Message-ID: <535E319A.9050104@ti.com> Date: Mon, 28 Apr 2014 13:46:50 +0300 From: Peter Ujfalusi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Lee Jones CC: , , , Subject: Re: [PATCH] mfd: twl6040: Optional clk32k clock handling References: <1396522482-32036-1-git-send-email-peter.ujfalusi@ti.com> <20140428103629.GI21279@lee--X1> In-Reply-To: <20140428103629.GI21279@lee--X1> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 going 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/Documentation/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: >> >> 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" >> >> 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; >> >> + clk_prepare_enable(twl6040->clk32k); >> + >> /* Allow writes to the chip */ >> regcache_cache_only(twl6040->regmap, false); >> >> @@ -346,6 +348,8 @@ int twl6040_power(struct twl6040 *twl6040, int on) >> >> twl6040->sysclk = 0; >> twl6040->mclk = 0; >> + >> + clk_disable_unprepare(twl6040->clk32k); >> } >> >> out: >> @@ -644,6 +648,12 @@ static int twl6040_probe(struct i2c_client *client, >> >> i2c_set_clientdata(client, twl6040); >> >> + twl6040->clk32k = devm_clk_get(&client->dev, "clk32k"); >> + if (IS_ERR(twl6040->clk32k)) { >> + dev_info(&client->dev, "clk32k is not handled\n"); >> + twl6040->clk32k = NULL; > > So what happens if you pass a NULL clk reference to clk_prepare_enable()? 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. -- Péter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/