From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Lunn Subject: Re: [PATCH v2 3/5] drivers: net: phy: Add MDIO driver Date: Thu, 7 Jul 2016 16:03:02 +0200 Message-ID: <20160707140302.GP19800@lunn.ch> References: <1464739840-21971-1-git-send-email-isubramanian@apm.com> <1464739840-21971-4-git-send-email-isubramanian@apm.com> <20160601011148.GD31982@lunn.ch> <20160705134950.GC5230@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Iyappan Subramanian Cc: David Miller , netdev , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , patches , Matthias Brugger List-Id: devicetree@vger.kernel.org > Wed, Jul 06, 2016 at 04:44:44PM -0700, Iyappan Subramanian wrote: > Hi Andrew, > > On Tue, Jul 5, 2016 at 6:49 AM, Andrew Lunn wrote: > > On Mon, Jun 06, 2016 at 10:12:35AM -0700, Iyappan Subramanian wrote: > >> Hi Andrew, > >> > >> Thanks for the review. > >> > >> On Tue, May 31, 2016 at 6:11 PM, Andrew Lunn wrote: > >> > On Tue, May 31, 2016 at 05:10:38PM -0700, Iyappan Subramanian wrote: > >> >> +static int xgene_mdio_reset(struct xgene_mdio_pdata *pdata) > >> >> +{ > >> >> + int ret; > >> >> + > >> >> + if (pdata->mdio_id == XGENE_MDIO_RGMII) { > >> >> + if (pdata->dev->of_node) { > >> >> + clk_prepare_enable(pdata->clk); > >> >> + clk_disable_unprepare(pdata->clk); > >> >> + clk_prepare_enable(pdata->clk); > >> > > >> > Hi Iyappan > >> > > >> > Is that a workaround for a hardware problem? If so, i would suggest > >> > adding a comment, to stop people submitting a patch simplifying it. > >> > >> Hardware expects this clock sequence. I'll add comment as you suggested. > > > > What exactly does the hardware require? Is this a workaround for a bug > > in the clock generator? Or a workaround for a bug in the MDIO device? > > Hardware requires a clock pulse. There is no bug. And how are you guaranteeing a pulse? You enable/disable/enable without any sleeps, so it could all happen within a single clock cycle? Andrew -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html