From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754708AbcFTMHC (ORCPT ); Mon, 20 Jun 2016 08:07:02 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:60786 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753874AbcFTMG7 (ORCPT ); Mon, 20 Jun 2016 08:06:59 -0400 Message-ID: <1466424354.6070.41.camel@pengutronix.de> Subject: Re: [PATCH 2/2] mtd: nand: sunxi: add reset line support From: Philipp Zabel To: Boris Brezillon Cc: Icenowy Zheng , maxime.ripard@free-electrons.com, wens@csie.org, robh+dt@kernel.org, richard@nod.at, dwmw2@infradead.org, computersforpeace@gmail.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-sunxi@googlegroups.com Date: Mon, 20 Jun 2016 14:05:54 +0200 In-Reply-To: <20160619140652.07ab03c9@bbrezillon> References: <20160619113739.30362-1-icenowy@aosc.xyz> <20160619113739.30362-2-icenowy@aosc.xyz> <20160619140652.07ab03c9@bbrezillon> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.9-1+b1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:100:96de:80ff:fec2:9969 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Sonntag, den 19.06.2016, 14:06 +0200 schrieb Boris Brezillon: > +Philipp > > On Sun, 19 Jun 2016 19:37:39 +0800 > Icenowy Zheng wrote: > > > The NAND controller on some sun8i chips needs its reset line to be deasserted > > before they can enter working state. This commit added the reset line process > > to the driver. > > > > Signed-off-by: Icenowy Zheng > > --- > > drivers/mtd/nand/sunxi_nand.c | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c > > index a83a690..1502748 100644 > > --- a/drivers/mtd/nand/sunxi_nand.c > > +++ b/drivers/mtd/nand/sunxi_nand.c > > @@ -39,6 +39,7 @@ > > #include > > #include > > #include > > +#include > > > > #define NFC_REG_CTL 0x0000 > > #define NFC_REG_ST 0x0004 > > @@ -269,6 +270,7 @@ struct sunxi_nfc { > > void __iomem *regs; > > struct clk *ahb_clk; > > struct clk *mod_clk; > > + struct reset_control *reset; > > unsigned long assigned_cs; > > unsigned long clk_rate; > > struct list_head chips; > > @@ -1871,6 +1873,18 @@ static int sunxi_nfc_probe(struct platform_device *pdev) > > if (ret) > > goto out_ahb_clk_unprepare; > > > > + nfc->reset = devm_reset_control_get_optional(dev, "ahb"); > > + if (PTR_ERR(nfc->reset) == -EPROBE_DEFER) > > + return PTR_ERR(nfc->reset); > > Actually you should test for != -ENOENT, because all error codes except > this one should stop the ->probe(). > > BTW, this devm_reset_control_get_optional() is really weird. While most > _optional() methods return NULL when the element is not defined in the > DT, this one returns -ENOTENT, which makes it impossible to > differentiate a real error from a undefined reset line (which is a > valid case for _optional()). Of course it's possible, -ENOENT is only returned if the reset line is not defined in the device tree. Note that gpiod_get_(index_)optional do nothing more that replacing -ENOENT with NULL. And phydev_optional_get replaces -ENODEV with NULL. And regulator_get_optional, if I understand it correctly, never returns NULL. > Philipp, is there a good reason for doing that? Historically, NULL has not been a valid value for rstc. I suppose we could add NULL checks to the reset_control_assert/deassert/reset/status functions and align the reset API a bit with gpiod. I just wouldn't want to see any IS_ERR_OR_NULL error handling in the drivers. regards Philipp