From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Wed, 09 Jun 2021 10:56:40 +0200 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by lore.white.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1lqu0u-0005eN-Lg for lore@lore.pengutronix.de; Wed, 09 Jun 2021 10:56:40 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:e::133]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lqu0t-00060W-8c for lore@pengutronix.de; Wed, 09 Jun 2021 10:56:40 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:Cc:To:Subject:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; 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Wed, 09 Jun 2021 10:04:55 +0200 To: Sascha Hauer Cc: Barebox List References: <20210607141057.23255-1-s.hauer@pengutronix.de> <20210607222233.GB5267@pengutronix.de> <2166dc52-64da-14bb-987c-7000c31c6882@pengutronix.de> <20210608085817.GD5267@pengutronix.de> From: Ahmad Fatoum Message-ID: <9d974bdd-ec8f-fc6f-473c-19f2110917f0@pengutronix.de> Date: Wed, 9 Jun 2021 10:04:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210608085817.GD5267@pengutronix.de> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210609_010457_434894_5CAADC2F X-CRM114-Status: GOOD ( 35.96 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:e::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.ext.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-4.6 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 1/2] net: designware: eqos: reset phy X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.ext.pengutronix.de) On 08.06.21 10:58, Sascha Hauer wrote: > On Tue, Jun 08, 2021 at 09:31:03AM +0200, Ahmad Fatoum wrote: >> Hello Sascha, >> >> On 08.06.21 00:22, Sascha Hauer wrote: >>> On Mon, Jun 07, 2021 at 05:59:02PM +0200, Ahmad Fatoum wrote: >>>> Hello Sascha, >>>> >>>> On 07.06.21 16:10, Sascha Hauer wrote: >>>>> The designware eqos DT binding has support for specifying reset GPIOs. >>>>> Add support for them. >>>>> >>>>> Signed-off-by: Sascha Hauer >>>>> --- >>>>> drivers/net/designware_eqos.c | 33 +++++++++++++++++++++++++++++++++ >>>>> drivers/of/of_gpio.c | 7 +++++++ >>>>> 2 files changed, 40 insertions(+) >>>>> >>>>> diff --git a/drivers/net/designware_eqos.c b/drivers/net/designware_eqos.c >>>>> index d2baaeaf63..0321024169 100644 >>>>> --- a/drivers/net/designware_eqos.c >>>>> +++ b/drivers/net/designware_eqos.c >>>>> @@ -8,9 +8,11 @@ >>>>> >>>>> #include >>>>> #include >>>>> +#include >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>>> #include >>>>> #include >>>>> #include >>>>> @@ -189,6 +191,33 @@ struct eqos_desc { >>>>> >>>>> #define MII_BUSY (1 << 0) >>>>> >>>>> +static int eqos_phy_reset(struct device_d *dev, struct eqos *eqos) >>>>> +{ >>>>> + int phy_reset; >>>>> + int ret; >>>>> + u32 delays[3] = { 0, 0, 0 }; >>>>> + >>>>> + phy_reset = of_get_named_gpio(dev->device_node, "snps,reset-gpio", 0); >>>>> + >>>>> + if (!gpio_is_valid(phy_reset)) >>>>> + return 0; >>>> >>>> Whitespace is wrong. >>>> >>>>> + >>>>> + ret = gpio_request(phy_reset, "phy-reset"); >>>>> + if (ret) >>>>> + return ret; >>>> >>>> Can you use gpiod_get instead? This would reduce the boilerplate here. >>> >>> Sure. I didn't realize I don't honour the active high/low flags the way >>> I did it. >>> >>>> >>>>> + >>>>> + of_property_read_u32_array(dev->device_node, >>>>> + "snps,reset-delays-us", >>>>> + delays, ARRAY_SIZE(delays)); >>>>> + >>>> >>>> Looks strange to read out a delay and not act on it. I'd prefer >>>> waiting delays[0] here. >>> >>> Yes, it looks strange, but that's because the binding doesn't make much >>> sense. Why should I insert a delay before doing anything? >> >> .--------. >> >> POR --------->|R flip |---- Regulator ----> PHY VDD >> >> .->|S flop | >> >> | `--------' >> >> | >> >> | >> >> | >> >> RESET GPIO -----'`-------------------------------> PHY Reset >> >> (active low) >> >> It's stupid, but it works with Linux and wouldn't with barebox >> (if PHY VDD takes too long to stabilize)... ^^' > > What we are doing is: > > 1) RESET_GPIO has unknown state > 2) gpio_request() > 3) RESET_GPIO has the same unknown state Linux requests with devm_gpiod_get_optional(..., GPIOD_OUT_LOW), so it's inactive here (== HIGH, which enables flip flop) > 4) udelay(delays[0]) > 5) RESET_GPIO still has the same unknown state Voltage has a while to stabilize while RESET GPIO is inactive here. > 6) gpio_set_active() > 7) RESET_GPIO puts phy into reset > > Your FLIPFLOP will also only set its output at step 7), so your > regulator stabilization time begins at 7), you would still have > to make delays[1] long enough for the regulator to stabilize and > the phy come up. > What matters here is the point where we put RESET_GPIO into a known > state. Whether you do step 4) or leave it out makes no difference. > >> >>> I can a delay here, it wouldn't make much difference as all users except >>> one specify zero delay here anyway. For the one exception I would bet >>> someone has inserted the first delay without a good reason, they are all >>> 10000. >> >> That's probably true. I still think mimicking Linux' interpretation >> of bindings is a good general rule to follow. > > As long as they make sense, yes. > >> >>>> >>>>> + gpio_direction_active(phy_reset, 0); >>>> >>>> This always sets logical zero, because gpio_request above doesn't >>>> accept a flag telling it otherwise. You'll need of_get_named_gpio_flags >>>> here, at which point, you'll have basically open-coded gpiod_get(), so >>>> you could use that. >>> >>> Right. >>> >>>> >>>>> + udelay(delays[1]); >>>> >>>> Linux rounds up to 1 msec granularity here. We should do likewise. >>> >>> I don't see a good reason for that. The Linux driver used udelay() >>> initially, that was changed to msleep as the times were too long for >>> busy waiting. I have no clue why the author didn't use usleep_range >>> instead. >> >> Same reason: Device trees are tested with Linux. They've a better chance >> of just working when we round up wait times the same way. > > I am generally with you, but in this case the binding is very clear and > if you find a bug in the dts with this case, then be happy and fix it. > > Sascha > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox