From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH RFC 5/5] ahci_imx: add disable for spread-spectrum Date: Wed, 16 Apr 2014 23:57:21 +0100 Message-ID: <20140416225721.GP24070@n2100.arm.linux.org.uk> References: <20140416084227.GD24070@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-ide-owner@vger.kernel.org To: Rob Herring Cc: "linux-arm-kernel@lists.infradead.org" , Shawn Guo , Sascha Hauer , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Tejun Heo , "devicetree@vger.kernel.org" , linux-ide@vger.kernel.org List-Id: devicetree@vger.kernel.org On Wed, Apr 16, 2014 at 05:46:47PM -0500, Rob Herring wrote: > On Wed, Apr 16, 2014 at 3:43 AM, Russell King > wrote: > > Spread-spectrum doesn't work with Cubox-i hardware, so we have to > > disable this feature. Add a DT property so that platforms can > > indicate that this feature should not be enabled. > > This is for spread-spectrum tx or rx? Transmit SS is optional to > support, but the receiver must support SS. Otherwise random drives > won't work which makes for a good user experience. Is this really a > board quirk rather than a Si issue? No idea. This bit controls clock generation, and one reason given to disable it is if the reference clock being supplied is already spread spectrum. I don't think that applies here. It doesn't say which clock(s) this is applied to - I would guess it's the transmit clock. All I know is that with SS enabled, the drive is not detected, and SolidRun's original port disables SS. Disabling SS allows the external drive to be detected. I have no capability to check the eye pattern, so I've no idea if there's a problem with the electrical setup which stops SS from working. All I know is with the parameters I give here (which are those which SolidRun's original port uses) and with SS disabled, it works. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it.