From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D36FC55178 for ; Tue, 27 Oct 2020 13:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D60482076A for ; Tue, 27 Oct 2020 13:02:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751639AbgJ0NCe (ORCPT ); Tue, 27 Oct 2020 09:02:34 -0400 Received: from mga12.intel.com ([192.55.52.136]:40922 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2440804AbgJ0NCd (ORCPT ); Tue, 27 Oct 2020 09:02:33 -0400 IronPort-SDR: etGgZYkFCOYcT0UEtb826S4RqTbMVB1B6djlOp4UCL9mXKG0nG1+nt6402142vVGxertHxVGJ4 XkhwdmXcsWcw== X-IronPort-AV: E=McAfee;i="6000,8403,9786"; a="147357249" X-IronPort-AV: E=Sophos;i="5.77,423,1596524400"; d="scan'208";a="147357249" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Oct 2020 06:02:08 -0700 IronPort-SDR: kHdz/ktvsii3t9245pqWNz7zKyJpzsg81WqSKMK6y085wpfSOdb1fFalG019Jm3Lx1XULnkx3f WH5D0+kPxr5w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,423,1596524400"; d="scan'208";a="468289779" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.94]) ([10.237.72.94]) by orsmga004.jf.intel.com with ESMTP; 27 Oct 2020 06:02:05 -0700 Subject: Re: [PATCH v2] mmc: sdhci-acpi: AMDI0040: Allow changing HS200/HS400 driver strength To: Victor Ding , linux-kernel@vger.kernel.org Cc: Ulf Hansson , Raul E Rangel , linux-mmc@vger.kernel.org References: <20201027084612.528301-1-victording@google.com> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: <468bfe68-6595-0792-0ccc-3971aeca5478@intel.com> Date: Tue, 27 Oct 2020 15:01:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201027084612.528301-1-victording@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/10/20 10:46 am, Victor Ding wrote: > From: Raul E Rangel > > This change will allow platform designers better control over signal > integrity by allowing them to tune the HS200 and HS400 driver strengths. > > The driver strength was previously hard coded to A to solve boot > problems with certain platforms. This driver strength does not > universally apply to all platforms so we need a knob to adjust it. > > All older platforms currently have the SDR104 preset hard coded to A in > the firmware. This means that switching from the hard coded value in > the kernel to reading the SDR104 preset is a no-op for these platforms. > Newer platforms will have properly set presets. So this change will > support both new and old platforms. > > Signed-off-by: Raul E Rangel > Signed-off-by: Victor Ding Apart from unnecessary blank line after "return preset_driver_strength;" Acked-by: Adrian Hunter > > --- > > Changes in v2: > By Victor Ding > - Rebased the patch by using FIELD_GET for preset value bit masks. > - (No functional changes). > > The original patch was developed by Raul E Rangel. > https://patchwork.kernel.org/project/linux-mmc/patch/20200928154718.2.Ic6b6031366f090393d00a53fd69e1ada31ceb29e@changeid/ > > drivers/mmc/host/sdhci-acpi.c | 39 ++++++++++++++++++++++++++++++++--- > 1 file changed, 36 insertions(+), 3 deletions(-) > > diff --git a/drivers/mmc/host/sdhci-acpi.c b/drivers/mmc/host/sdhci-acpi.c > index 54205e3be9e8..225cb34cf1b9 100644 > --- a/drivers/mmc/host/sdhci-acpi.c > +++ b/drivers/mmc/host/sdhci-acpi.c > @@ -5,6 +5,7 @@ > * Copyright (c) 2012, Intel Corporation. > */ > > +#include > #include > #include > #include > @@ -545,10 +546,42 @@ struct amd_sdhci_host { > > static int amd_select_drive_strength(struct mmc_card *card, > unsigned int max_dtr, int host_drv, > - int card_drv, int *drv_type) > + int card_drv, int *host_driver_strength) > { > - *drv_type = MMC_SET_DRIVER_TYPE_A; > - return MMC_SET_DRIVER_TYPE_A; > + struct sdhci_host *host = mmc_priv(card->host); > + u16 preset, preset_driver_strength; > + > + /* > + * This method is only called by mmc_select_hs200 so we only need to > + * read from the HS200 (SDR104) preset register. > + * > + * Firmware that has "invalid/default" presets return a driver strength > + * of A. This matches the previously hard coded value. > + */ > + preset = sdhci_readw(host, SDHCI_PRESET_FOR_SDR104); > + preset_driver_strength = FIELD_GET(SDHCI_PRESET_DRV_MASK, preset); > + > + /* > + * We want the controller driver strength to match the card's driver > + * strength so they have similar rise/fall times. > + * > + * The controller driver strength set by this method is sticky for all > + * timings after this method is called. This unfortunately means that > + * while HS400 tuning is in progress we end up with mismatched driver > + * strengths between the controller and the card. HS400 tuning requires > + * switching from HS400->DDR52->HS->HS200->HS400. So the driver mismatch > + * happens while in DDR52 and HS modes. This has not been observed to > + * cause problems. Enabling presets would fix this issue. > + */ > + *host_driver_strength = preset_driver_strength; > + > + /* > + * The resulting card driver strength is only set when switching the > + * card's timing to HS200 or HS400. The card will use the default driver > + * strength (B) for any other mode. > + */ > + return preset_driver_strength; > + Unnecessary blank line. > } > > static void sdhci_acpi_amd_hs400_dll(struct sdhci_host *host, bool enable) >