From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anatolij Gustschin Subject: Re: i2c-mpc.c clock/speed Date: Wed, 5 Mar 2014 18:00:24 +0100 Message-ID: <20140305180024.0844df2d@crub> References: <5316EE78.2080808@antcom.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5316EE78.2080808-uj/7R2tJ6VmzQB+pC5nmwQ@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Roland Stigge Cc: "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , gsi-ynQEQJNshbs@public.gmane.org, Wolfram Sang List-Id: linux-i2c@vger.kernel.org Hi Roland, On Wed, 05 Mar 2014 10:29:28 +0100 Roland Stigge wrote: > Hi, > > in mpc_i2c_get_fdr_8xxx(), we have: > > ... > if (of_device_is_compatible(node, "fsl,mpc8544-i2c")) > prescaler = mpc_i2c_get_sec_cfg_8xxx() ? 3 : 2; > if (!prescaler) > prescaler = 1; > ... > > By restricting to "fsl,mpc8544-i2c", measured I2C speed on fsl p2020 is > only half as fast as configured (w/ prescaler = 1). > > In DT (arch/powerpc/boot/dts/fsl/pq3-i2c-0.dtsi), we have "fsl-i2c" > (i.e., generic), for Freescale boards. > > What would be the best solution here? Additional "compatible" strings, > e.g. "fsl,p1020-i2c" and adjusting i2c-mpc.c and DT? Or removing the > restriction to "fsl,mpc8544-i2c", i.e. calling > mpc_i2c_get_sec_cfg_8xxx() unconditionally? we can't remove this mpc8544e specific check here, it checks the SEC_CFG bit 24 in the PORDEVSR2 register, on other mpc8xxx cpus this register is either not present or the meaning of the bit 24 in this register is different. Adding "fsl,p1020-i2c" compatible and adjusting the driver would be okay. Thanks, Anatolij