From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753733AbaBDJPN (ORCPT ); Tue, 4 Feb 2014 04:15:13 -0500 Received: from top.free-electrons.com ([176.31.233.9]:55124 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751310AbaBDJPE (ORCPT ); Tue, 4 Feb 2014 04:15:04 -0500 Date: Tue, 4 Feb 2014 10:13:16 +0100 From: Maxime Ripard To: Chen-Yu Tsai Cc: Emilio Lopez , Mike Turquette , linux-arm-kernel , linux-sunxi , devicetree , linux-kernel Subject: Re: [PATCH v3 2/8] ARM: dts: sun7i: Add GMAC clock node to sun7i DTSI Message-ID: <20140204091316.GJ25625@lukather> References: <1391398346-5094-1-git-send-email-wens@csie.org> <1391398346-5094-3-git-send-email-wens@csie.org> <20140203193431.GD25625@lukather> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="VSaCG/zfRnOiPJtU" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --VSaCG/zfRnOiPJtU Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 04, 2014 at 11:06:24AM +0800, Chen-Yu Tsai wrote: > On Tue, Feb 4, 2014 at 3:34 AM, Maxime Ripard > wrote: > > On Mon, Feb 03, 2014 at 11:32:20AM +0800, Chen-Yu Tsai wrote: > >> The GMAC uses 1 of 2 sources for its transmit clock, depending on the > >> PHY interface mode. Add both sources as dummy clocks, and as parents > >> to the GMAC clock node. > >> > >> Signed-off-by: Chen-Yu Tsai > >> --- > >> arch/arm/boot/dts/sun7i-a20.dtsi | 28 ++++++++++++++++++++++++++++ > >> 1 file changed, 28 insertions(+) > >> > >> diff --git a/arch/arm/boot/dts/sun7i-a20.dtsi b/arch/arm/boot/dts/sun7= i-a20.dtsi > >> index 1595e9a..fc7f470 100644 > >> --- a/arch/arm/boot/dts/sun7i-a20.dtsi > >> +++ b/arch/arm/boot/dts/sun7i-a20.dtsi > >> @@ -314,6 +314,34 @@ > >> }; > >> > >> /* > >> + * The following two are dummy clocks, placeholders used > >> + * on gmac_tx clock. The actual frequency and availabili= ty > >> + * depends on the external PHY, operation mode and link > >> + * speed. > >> + */ > > > > If it depends on the external PHY, I guess that means it also depends > > on the board, right? Or is the GMAC supposed to always have that clock > > running at 25MHz, no matter what PHY is connected to it? >=20 > What I meant in the comment is that we cannot control the actual clock > rate of the TX clock. We can only select the source, and this is what > gmac_tx clock does. It is just a clock mux. The 125MHz and 25MHz clock > rates are used by the clk_set_rate in the stmmac glue layer to do > auto-reparenting. >=20 > The board dependent factor is what _type_ of PHY it is using, i.e. > MII, GMII, or RGMII. If it's MII, the PHY should provide the clock. > If it's RGMII, the internal clock would be used. GMII is a mix of > both. The actual clock rate depends on the link speed. >=20 > I should rephrase the comment along the lines of: >=20 > The following two are dummy clocks, placeholders used in the gmac_tx > clock. The gmac driver will choose one parent depending on the PHY > interface mode, using clk_set_rate auto-reparenting. > The actual TX clock rate is not controlled by the gmac_tx clock. Ok, thanks for the clarification. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --VSaCG/zfRnOiPJtU Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) iQIcBAEBAgAGBQJS8K8sAAoJEBx+YmzsjxAgiPwP/1AO1R8VKNB3hj+0BogRrf/k 7LK0/RlU1y+/hKJk4XxNOKvNcNkKCn9hoWBZ14HFJYNLjCSHKspb+9axRLtsCxLe g4k2Tq2ci7gNEYSXMq05yCg3hHX8o9eszNHhuQ4bfkX0qgv8mpSMA25T2d4ghB21 kkiEymtnaeMjOw6OWwkydtX57JFTT+Yz6dS0h0XCnXEEL2FojYQbdYYq+Hz1D3Ga EjtowC56W+jfzotuPkhq9YPx8djyIt2e+hc4Om7Lq3r/bi2ZlIyLgvY4TCcfRiam xNw7bUjOjGfijsLepGseV9RPpwa4ocOLI9FljCf7IkSCEx1tyJxe4ocbq/IY+Kyk /Wo8QS3XE3pRs40ZuAd9yxXk+9bqX5izlaslNEG1CrQTFlf67njHYhcCrhlvtq6x J2R79CaS4KBMSNDCZtUcX50bwOGbZ0VJeUafEvTAb5SYVsAkZExkO15P6TzzSoUo 9FyKXSOEsyvYCW00M8nIkMgfKtv1Yf9ZSanqSUOGp6UjVP+rRyLIZoMQYIWTAdgV LKmRuePoubeJ6DLk1sMY/1sCNU2FLaV6/twDi9xKzbRtHnG3BqCG/XjqyVtRj6mG JbcvC9q4VI1RK7D9XTBxEOOJIYXKe8xXyOvx0GVRJaFw8w4sAeXgJhz19TQoCccl YYtkxunK+jxWS1HMBNli =iFvB -----END PGP SIGNATURE----- --VSaCG/zfRnOiPJtU--