From patchwork Thu Jan 26 09:05:56 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxime Ripard X-Patchwork-Id: 9538555 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A4190601D7 for ; Thu, 26 Jan 2017 09:10:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 94ADF281C3 for ; Thu, 26 Jan 2017 09:10:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 875B628249; Thu, 26 Jan 2017 09:10:02 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0F92D2824F for ; Thu, 26 Jan 2017 09:10:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751513AbdAZJJX (ORCPT ); Thu, 26 Jan 2017 04:09:23 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:46021 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753085AbdAZJGS (ORCPT ); Thu, 26 Jan 2017 04:06:18 -0500 Received: by mail.free-electrons.com (Postfix, from userid 110) id CD8EA20DAA; Thu, 26 Jan 2017 10:06:13 +0100 (CET) Received: from localhost (LStLambert-657-1-97-87.w90-63.abo.wanadoo.fr [90.63.216.87]) by mail.free-electrons.com (Postfix) with ESMTPSA id A22A2206DB; Thu, 26 Jan 2017 10:06:13 +0100 (CET) From: Maxime Ripard To: Chen-Yu Tsai , Maxime Ripard , Ulf Hansson Cc: Rob Herring , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org, Andre Przywara Subject: [PATCH v4 3/13] mmc: sunxi: Always set signal delay to 0 for A64 Date: Thu, 26 Jan 2017 10:05:56 +0100 Message-Id: <6c9dae7e6c872420e5e565efb334be411269be21.1485421557.git-series.maxime.ripard@free-electrons.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-mmc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Experience have shown that the using the autocalibration could severely degrade the performances of the MMC bus. Allwinner is using in its BSP a delay set to 0 for all the modes but HS400. Remove the calibration code for now, and add comments to document our findings. Reviewed-by: Andre Przywara Signed-off-by: Maxime Ripard --- drivers/mmc/host/sunxi-mmc.c | 50 ++++++++++++------------------------- 1 file changed, 17 insertions(+), 33 deletions(-) diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c index 019f95e8e7c5..b9c8a62bc212 100644 --- a/drivers/mmc/host/sunxi-mmc.c +++ b/drivers/mmc/host/sunxi-mmc.c @@ -683,41 +683,19 @@ static int sunxi_mmc_oclk_onoff(struct sunxi_mmc_host *host, u32 oclk_en) static int sunxi_mmc_calibrate(struct sunxi_mmc_host *host, int reg_off) { - u32 reg = readl(host->reg_base + reg_off); - u32 delay; - unsigned long timeout; - if (!host->cfg->can_calibrate) return 0; - reg &= ~(SDXC_CAL_DL_MASK << SDXC_CAL_DL_SW_SHIFT); - reg &= ~SDXC_CAL_DL_SW_EN; - - writel(reg | SDXC_CAL_START, host->reg_base + reg_off); - - dev_dbg(mmc_dev(host->mmc), "calibration started\n"); - - timeout = jiffies + HZ * SDXC_CAL_TIMEOUT; - - while (!((reg = readl(host->reg_base + reg_off)) & SDXC_CAL_DONE)) { - if (time_before(jiffies, timeout)) - cpu_relax(); - else { - reg &= ~SDXC_CAL_START; - writel(reg, host->reg_base + reg_off); - - return -ETIMEDOUT; - } - } - - delay = (reg >> SDXC_CAL_DL_SHIFT) & SDXC_CAL_DL_MASK; - - reg &= ~SDXC_CAL_START; - reg |= (delay << SDXC_CAL_DL_SW_SHIFT) | SDXC_CAL_DL_SW_EN; - - writel(reg, host->reg_base + reg_off); - - dev_dbg(mmc_dev(host->mmc), "calibration ended, reg is 0x%x\n", reg); + /* + * FIXME: + * This is not clear how the calibration is supposed to work + * yet. The best rate have been obtained by simply setting the + * delay to 0, as Allwinner does in its BSP. + * + * The only mode that doesn't have such a delay is HS400, that + * is in itself a TODO. + */ + writel(SDXC_CAL_DL_SW_EN, host->reg_base + reg_off); return 0; } @@ -809,7 +787,13 @@ static int sunxi_mmc_clk_set_rate(struct sunxi_mmc_host *host, if (ret) return ret; - /* TODO: enable calibrate on sdc2 SDXC_REG_DS_DL_REG of A64 */ + /* + * FIXME: + * + * In HS400 we'll also need to calibrate the data strobe + * signal. This should only happen on the MMC2 controller (at + * least on the A64). + */ return sunxi_mmc_oclk_onoff(host, 1); }