From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hqemgate14.nvidia.com ([216.228.121.143]:15079 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750789AbcFNO6E (ORCPT ); Tue, 14 Jun 2016 10:58:04 -0400 Date: Tue, 14 Jun 2016 17:57:56 +0300 From: Peter De Schrijver To: Thierry Reding CC: Alexandre Courbot , Rhyland Klein , Jon Hunter , , Subject: Re: [PATCH 1/3] clk: tegra: Disable spread spectrum on pll_d2 Message-ID: <20160614145756.GE12863@tbergstrom-lnx.Nvidia.com> References: <20160614120044.30734-1-thierry.reding@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <20160614120044.30734-1-thierry.reding@gmail.com> Sender: linux-clk-owner@vger.kernel.org List-ID: On Tue, Jun 14, 2016 at 02:00:42PM +0200, Thierry Reding wrote: > From: Thierry Reding > > Enabling spread spectrum on pll_d2 can lead to issues with display > modes. HDMI monitors, for example, would report "Signal Error" and > some modes driven over DisplayPort would generate fuzzy horizontal > bands. > Acked-by: Peter De Schrijver The only display clock we should enable spread spectrum for, is pll_dp. AFAIK the DP spec specifies the amount of spread which can be tolerated. Peter. > Signed-off-by: Thierry Reding > --- > drivers/clk/tegra/clk-tegra210.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c > index 6bd1235d09b1..cd141a364c9d 100644 > --- a/drivers/clk/tegra/clk-tegra210.c > +++ b/drivers/clk/tegra/clk-tegra210.c > @@ -1914,8 +1914,9 @@ static struct tegra_clk_pll_params pll_d2_params = { > .sdm_din_mask = PLLA_SDM_DIN_MASK, > .sdm_ctrl_reg = PLLD2_MISC1, > .sdm_ctrl_en_mask = PLLD2_SDM_EN_MASK, > - .ssc_ctrl_reg = PLLD2_MISC1, > - .ssc_ctrl_en_mask = PLLD2_SSC_EN_MASK, > + /* disable spread-spectrum for pll_d2 */ > + .ssc_ctrl_reg = 0, > + .ssc_ctrl_en_mask = 0, > .round_p_to_pdiv = pll_qlin_p_to_pdiv, > .pdiv_tohw = pll_qlin_pdiv_to_hw, > .div_nmp = &pllss_nmp, > -- > 2.8.3 >