From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko Stuebner Subject: Re: [PATCH] i2c: rk3x: init module as subsys call Date: Tue, 05 Jan 2016 08:02:41 +0100 Message-ID: <2513923.8oltbpbAin@phil> References: <1451962938-17398-1-git-send-email-jay.xu@rock-chips.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: Received: from gloria.sntech.de ([95.129.55.99]:56083 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751722AbcAEHC4 (ORCPT ); Tue, 5 Jan 2016 02:02:56 -0500 In-Reply-To: <1451962938-17398-1-git-send-email-jay.xu@rock-chips.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: "jianqun.xu" Cc: wsa@the-dreams.de, wdc@rock-chips.com, huangtao@rock-chips.com, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Hi Jianqun, Am Dienstag, 5. Januar 2016, 11:02:18 schrieb jianqun.xu: > From: Xu Jianqun > > There is a requirement from pmic device, which is on the i2c bus, > that the pmic needs to be called earlier then devices powered by > the outputs of the pmic, if not, the devices maybe fail to probe. > > For example, a pmic on i2c0, and touchscreen device on i2c2, > i2c0: - pmic(rk818) > i2c2: - ts(gt911), powered by rk818 on i2c0 > > The problem will happen if the i2c2 node in dts file is ordered > before i2c0 node, then ts(gt911) will be probed before pmic(rk818), > since the power from the pmic(rk818) for ts(gt911) hasn't enabled, > so ts(gt911) will fail to probe due to the failure of i2c test. > > But if we set the i2c0 node before i2c2, there is no this issue. > > The stable way to make sure that pmic can be intalized before other > peripher devices is to make the pmic module be subsys call, the i2c > module need to be subsys call firstly. I do believe that came up in the past already and the direction from then was (and most likely still is) that drivers should make use of the probe- deferral mechanism instead of wiggling with the initcall ordering. Your touchscreen will have a "xyz-supply" property and I think the regulator-framework should already emit a -EPROBE_DEFER at regulator_get, when the regulator is specified but not available yet. Heiko > > Signed-off-by: Xu Jianqun > --- > drivers/i2c/busses/i2c-rk3x.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c > index c1935eb..00e5959 100644 > --- a/drivers/i2c/busses/i2c-rk3x.c > +++ b/drivers/i2c/busses/i2c-rk3x.c > @@ -1037,7 +1037,17 @@ static struct platform_driver rk3x_i2c_driver = { > }, > }; > > -module_platform_driver(rk3x_i2c_driver); > +static int __init rk3x_i2c_init(void) > +{ > + return platform_driver_register(&rk3x_i2c_driver); > +} > +subsys_initcall(rk3x_i2c_init); > + > +static void __exit rk3x_i2c_exit(void) > +{ > + platform_driver_unregister(&rk3x_i2c_driver); > +} > +module_exit(rk3x_i2c_exit); > > MODULE_DESCRIPTION("Rockchip RK3xxx I2C Bus driver"); > MODULE_AUTHOR("Max Schwarz ");