From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] i2c: aspeed: Retain delay/setup/hold values when
 configuring bus frequency
Date: Wed, 16 Aug 2017 16:59:38 +1000
Message-ID: <1502866778.4493.84.camel@kernel.crashing.org>
References: <20170815072102.23067-1-andrew@aj.id.au>
         <CACPK8XeNDxo14KRsAqo3a0Rs26h-1vRsLyqSX+bt2jfZHq=5yA@mail.gmail.com>
         <247768a3-074f-70ad-6132-39d1443ce210@kaod.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Return-path: <linux-i2c-owner@vger.kernel.org>
Received: from gate.crashing.org ([63.228.1.57]:60332 "EHLO gate.crashing.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751530AbdHPHAh (ORCPT <rfc822;linux-i2c@vger.kernel.org>);
        Wed, 16 Aug 2017 03:00:37 -0400
In-Reply-To: <247768a3-074f-70ad-6132-39d1443ce210@kaod.org>
Sender: linux-i2c-owner@vger.kernel.org
List-Id: linux-i2c@vger.kernel.org
To: =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>, Joel Stanley <joel@jms.id.au>, Andrew Jeffery <andrew@aj.id.au>
Cc: Ryan Chen <ryan_chen@aspeedtech.com>, linux-aspeed@lists.ozlabs.org, Wolfram Sang <wsa@the-dreams.de>, OpenBMC Maillist <openbmc@lists.ozlabs.org>, Brendan Higgins <brendanhiggins@google.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-i2c@vger.kernel.org

On Wed, 2017-08-16 at 08:53 +0200, Cédric Le Goater wrote:
> > >          divisor = DIV_ROUND_UP(bus->parent_clk_frequency, bus->bus_frequency);
> > > -       clk_reg_val = bus->get_clk_reg_val(divisor);
> > > +       clk_reg_val = readl(bus->base + ASPEED_I2C_AC_TIMING_REG1);
> > > +       clk_reg_val &= (ASPEED_I2CD_TIME_TBUF_MASK |
> > > +                       ASPEED_I2CD_TIME_THDSTA_MASK |
> > > +                       ASPEED_I2CD_TIME_TACST_MASK);
> > 
> > Instead of keeping the u-boot values (which appear to be hard-coded),
> > should we instead put the known working values in the register?
> 
> Yes. I was wondering where the initial setting was from on the AST400.

Well, the AST2500 hard codes them in HW, so it makes some amount of
sense to use whatever aspeed platform.S hard codes in u-boot for the
2400. The values look reasonably sane.

If we ever see a need to change them, we can add DT props etc... but
for now I'd just not bother.

The way it is now, at least, if I have problems, I can tweak the values
with devmem and try again without the driver overwriting them :-)

Cheers,
Ben.