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Fri, 29 Mar 2019 08:33:34 -0700 (PDT) From: Jerome Brunet To: Neil Armstrong Subject: [PATCH 1/3] clk: meson: mpll: properly handle spread spectrum Date: Fri, 29 Mar 2019 16:33:23 +0100 Message-Id: <20190329153325.23869-2-jbrunet@baylibre.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190329153325.23869-1-jbrunet@baylibre.com> References: <20190329153325.23869-1-jbrunet@baylibre.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190329_083336_548655_28C0E3E8 X-CRM114-Status: GOOD ( 13.51 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-amlogic@lists.infradead.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, Jerome Brunet Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org The bit 'SSEN' available on some MPLL DSS outputs is not related to the fractional part of the divider but to the function called 'Spread Spectrum'. This function might be used to solve EM issues by adding a jitter on clock signal. This widens the signal spectrum and weakens the peaks in it. While spread spectrum might be useful for some application, it is problematic for others, such as audio. This patch introduce a new flag to the MPLL driver to enable (or not) the spread spectrum function. Fixes: 1f737ffa13ef ("clk: meson: mpll: fix mpll0 fractional part ignored") Signed-off-by: Jerome Brunet --- drivers/clk/meson/clk-mpll.c | 9 ++++++--- drivers/clk/meson/clk-mpll.h | 1 + 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/clk/meson/clk-mpll.c b/drivers/clk/meson/clk-mpll.c index 64d31c8ba3d0..2d39a8bc367c 100644 --- a/drivers/clk/meson/clk-mpll.c +++ b/drivers/clk/meson/clk-mpll.c @@ -141,9 +141,12 @@ static void mpll_init(struct clk_hw *hw) /* Enable the fractional part */ meson_parm_write(clk->map, &mpll->sdm_en, 1); - /* Set additional fractional part enable if required */ - if (MESON_PARM_APPLICABLE(&mpll->ssen)) - meson_parm_write(clk->map, &mpll->ssen, 1); + /* Set spread spectrum if possible */ + if (MESON_PARM_APPLICABLE(&mpll->ssen)) { + unsigned int ss = + mpll->flags & CLK_MESON_MPLL_SPREAD_SPECTRUM ? 1 : 0; + meson_parm_write(clk->map, &mpll->ssen, ss); + } /* Set the magic misc bit if required */ if (MESON_PARM_APPLICABLE(&mpll->misc)) diff --git a/drivers/clk/meson/clk-mpll.h b/drivers/clk/meson/clk-mpll.h index 2925fb939fdd..a991d568c43a 100644 --- a/drivers/clk/meson/clk-mpll.h +++ b/drivers/clk/meson/clk-mpll.h @@ -25,6 +25,7 @@ struct meson_clk_mpll_data { }; #define CLK_MESON_MPLL_ROUND_CLOSEST BIT(0) +#define CLK_MESON_MPLL_SPREAD_SPECTRUM BIT(1) extern const struct clk_ops meson_clk_mpll_ro_ops; extern const struct clk_ops meson_clk_mpll_ops; -- 2.20.1 _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic