Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755269AbbHFJA4 (ORCPT ); Thu, 6 Aug 2015 05:00:56 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:52865 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1754890AbbHFJAw (ORCPT ); Thu, 6 Aug 2015 05:00:52 -0400 X-Listener-Flag: 11101 Message-ID: <1438851644.27884.21.camel@mtksdaap41> Subject: Re: [PATCH v6 7/9] clk: mediatek: Add subsystem clocks of MT8173 From: James Liao To: Sascha Hauer , Daniel Kurtz CC: , Heiko Stubner , , Mike Turquette , Stephen Boyd , , "Ricky Liang" , Rob Herring , , Sascha Hauer , Matthias Brugger , Date: Thu, 6 Aug 2015 17:00:44 +0800 In-Reply-To: <20150806085354.GN18700@pengutronix.de> References: <1438676218-11310-1-git-send-email-jamesjj.liao@mediatek.com> <1438676218-11310-8-git-send-email-jamesjj.liao@mediatek.com> <20150805064605.GZ18700@pengutronix.de> <1438849431.27884.9.camel@mtksdaap41> <20150806085354.GN18700@pengutronix.de> Content-Type: text/plain; charset="us-ascii" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2983 Lines: 62 Hi Sascha, On Thu, 2015-08-06 at 10:53 +0200, Sascha Hauer wrote: > On Thu, Aug 06, 2015 at 04:23:51PM +0800, James Liao wrote: > > On Wed, 2015-08-05 at 08:46 +0200, Sascha Hauer wrote: > > > On Tue, Aug 04, 2015 at 04:16:56PM +0800, James Liao wrote: > > > > static const struct mtk_fixed_clk fixed_clks[] __initconst = { > > > > FIXED_CLK(CLK_TOP_CLKPH_MCK_O, "clkph_mck_o", "clk26m", 400 * MHZ), > > > > FIXED_CLK(CLK_TOP_USB_SYSPLL_125M, "usb_syspll_125m", "clk26m", 125 * MHZ), > > > > + FIXED_CLK(CLK_TOP_DSI0_DIG, "dsi0_dig", "clk26m", 130 * MHZ), > > > > + FIXED_CLK(CLK_TOP_DSI1_DIG, "dsi1_dig", "clk26m", 130 * MHZ), > > > > + FIXED_CLK(CLK_TOP_LVDS_PXL, "lvds_pxl", "lvdspll", 148.5 * MHZ), > > > > + FIXED_CLK(CLK_TOP_LVDS_CTS, "lvds_cts", "lvdspll", 51.975 * MHZ), > > > > > > I would expect 51975 * KHZ here to avoid fractional numbers. Probably > > > gcc calculates that during compile time so this will work as expected, > > > still I'm not sure this is good style to use fractional numbers here. > > > > As I know all constants will be calculated in compile time, so there > > should be no difference between 51.975 * MHZ and 51975 * KHz. > > > > > Anyway, on my system lvdspll is running at 150MHz. Are you sure there is > > > a clock derived from this running at 148.5MHz? Is it really correct to > > > use a fixed clock here or should it rather be lvdspll directly? > > > > Here is the clock hierarchy between lvdspll and lvds_pxl: > > > > -------- AD_VPLL_DPIX_CK -------- lvds_pxl ----- > > | |--------------------->| |---------->| > > | | | cksys | | > > LVDSPLL -->| LVDSTX | | buffer | | MMSYS > > | | AD_LVDSTX_CLKDIG_CTS | test | lvds_cts | > > | |--------------------->| |---------->| > > -------- -------- ----- > > > > Some clocks and blocks are not modeled into CCF. But we prefer to enable > > lvdspll before enabling lvds_pxl. So I modeled lvds_pxl (and lvds_cts) > > as a fixed-rate clock with a source from lvdspll. > > > > The frequency of these fixed-rate clocks (such as 148.5 MHz) are typical > > rate. In fact, we don't care about the actual rate of these clocks. We > > just care about the enable / disable sequence of them. > > Please either use the real rate or 0 (along with a explaining why). Using > a frequency with four to five significant digits makes me think that the > actual rate is very important. Oops, your suggestion is much different from Daniel's. Daniel, could you help to comment about how we model these clocks? Best regards, James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/