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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 30A45C43219 for ; Tue, 30 Apr 2019 20:02:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED1F42080C for ; Tue, 30 Apr 2019 20:02:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=googlemail.com header.i=@googlemail.com header.b="Yd6dh8YO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726667AbfD3UCk (ORCPT ); Tue, 30 Apr 2019 16:02:40 -0400 Received: from mail-oi1-f194.google.com ([209.85.167.194]:41434 "EHLO mail-oi1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725996AbfD3UCk (ORCPT ); Tue, 30 Apr 2019 16:02:40 -0400 Received: by mail-oi1-f194.google.com with SMTP id v23so12159825oif.8; Tue, 30 Apr 2019 13:02:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=3r147tIwezgftcMqyv0BTWw1GGds2ZC5ylXTysMayJ0=; b=Yd6dh8YODaH840dtnqB8JIV0ku0Zs+HUzPE4xdGMwqhIyvdVx0ZwwoCz/cYZK4bZY7 xTu677WYvvlU6yyq40DjghNCsKGr9UrNi6tynsVXL/IteW3aeOJVSxUg9c7SIRP0JC6K EGhqpYHFIFXbqdLC+YA9bR3PG2CdFwFEbAaKD0BNVNXjLlINmwyn8uC8kzQ0YIlqmlmb bm/sPNemBW7unwnpv37VGvMzXN+AAIEQUYj0hd4ekUmLEpS6erbEeVlfDKV/pCSwRVZQ mApszl2ASCmOfR0VkUK4+TLYr2DjvYnzzU9zFF+iPtYcHf+BK8v02E1kbrOEQZxuVOK/ q8eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=3r147tIwezgftcMqyv0BTWw1GGds2ZC5ylXTysMayJ0=; b=Yz68I+Qv/ADaZ5mtpoKxTtI+DRJ6TWO33pfuIKLyLBRyKUtHQ/cEtOxmaCP1HZRGYu lMJFanOslnZl/t4+xVKumZ3PSwu0MgwCttcyNhBOoMLE+tCdQwE6dG2kE7fLKq93CNjv dNJ0DI7UQO/l3EIAfd1VquZRsHvc2jgu8CzgcUIn3rA/KSV/D313/YQNdO4lNXHzgumJ AG/mii1wzsdPPmND4TyD1YUmfKnOsHxM0MOYtDKOUud6gfLGdGG01Jel2CWn9tVorqcV bWnG2MY6K35aJ3ftcQZ8K0xptFn5870my7DmWXLaMrMJECFdqqIHtFmKgl0H/Xt1aMbx PR+A== X-Gm-Message-State: APjAAAWT9UTxwlD2U3kSITUC4ycGZRahO/qrqH4rmTi7ZZZDKX1AXBFX Axm4BodwK2BvKmKeaBqcdFB/+xGZK6tCvd+88G4= X-Google-Smtp-Source: APXvYqwDdmSQ1hWlPEYCDngS4jp/HbPyU07MOy4Ce9TcozyHCzgare4Eydcg5I08aewFi4Jb4cXyXvgfpEdZ63bO/j4= X-Received: by 2002:aca:4482:: with SMTP id r124mr4474985oia.39.1556654558796; Tue, 30 Apr 2019 13:02:38 -0700 (PDT) MIME-Version: 1.0 References: <20190423090235.17244-1-jbrunet@baylibre.com> <20190423090235.17244-5-jbrunet@baylibre.com> <17c5978419c8778eb1f2c2a6e2aee66e864ac53d.camel@baylibre.com> <936229765eac2bcdacf9a53925bb17c38ea18e3a.camel@baylibre.com> In-Reply-To: <936229765eac2bcdacf9a53925bb17c38ea18e3a.camel@baylibre.com> From: Martin Blumenstingl Date: Tue, 30 Apr 2019 22:02:27 +0200 Message-ID: Subject: Re: [PATCH v2 4/7] mmc: meson-gx: disable HS400 To: Jerome Brunet Cc: Ulf Hansson , Kevin Hilman , linux-amlogic@lists.infradead.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jerome, On Mon, Apr 29, 2019 at 8:50 PM Jerome Brunet wrote: > > On Mon, 2019-04-29 at 20:31 +0200, Martin Blumenstingl wrote: > > Hi Jerome, > > > > On Mon, Apr 29, 2019 at 10:29 AM Jerome Brunet wrote: > > > On Sat, 2019-04-27 at 22:02 +0200, Martin Blumenstingl wrote: > > > > Hi Jerome, > > > > > > > > On Tue, Apr 23, 2019 at 11:03 AM Jerome Brunet wrote: > > > > > At the moment, all our attempts to enable HS400 on Amlogic chipsets have > > > > > been unsuccessful or unreliable. Until we can figure out how to enable this > > > > > mode safely and reliably, let's force it off. > > > > last year I have seen issues with HS400 on my Khadas VIM2: [0] > > > > have you tested all other patches from this series and HS400 is still > > > > not working for you? > > > > > > Because HS400 was never really stable to begin with. > > > It was a mistake to enable it on the VIM2 > > > > > > > I'm curious because this patch is early in the series and all the > > > > tuning fixes and improvements are after this patch. > > > > > > There are several reasons why this new tuning won't solve the HS400 problem: > > > - Signal resampling tuning granularity gets worse when rate rises. The resampling > > > is done using the input frequency. We can basically resample up to the value of > > > internal divider. > > > > > > In HS200 - Fin is 1GHz, Fout is 200MHz (1/5) so the resample range is [0, 4] > > > In HS400 - Fin should be fdiv5 (400MHZ) and in such case, no resampling is > > > possible (internal div = 1) > > > Even if we keep 1GHz, then out is 333MHz max giving a range of [0, 2] > > > that's not enough to tune > > this limitation would be great to have in the description of patch 7 > > from this series > > That's not really a limitation. I should probably not have mentioned as it it seems to > have made things even more unclear. I disabled HS400 before introducing the new tuning on > purpose. Any comment regarding hs400 does not belong in patch 7 IHMO. If you want > to add comment regarding hs400, I think it belongs here > > > > > > Going further, tuning the Rx path does not make much sense in HS400 since we > > > should be using the data strobe signal to account for the round trip delay of > > > the clock and correctly sample Rx. AFAICT, If there is a tuning to be done for > > > HS400, it is most likely linked to the data strobe. > > it would be great to have a better description as part of the commit > > message - with that you can add my: > > Acked-by: Martin Blumenstingl > > > > my proposal for an update patch description (apologies I have > > incorrectly summarized your findings): > > " > > At the moment, all our attempts to enable HS400 on Amlogic chipsets have > > been unsuccessful or unreliable: > > - signal resampling without delay adjustments and phase tuning for the > > RX and TX clocks (this caused CRC errors and hangs even without HS400 > > mode, for example on the Khadas VIM, Khadas VIM2 and libretech-cc > > boards) > > - signal resampling without delay adjustments and RX clock phase > > tuning (some HS200 and HS400 eMMC chips were not recognized, for > > example on the Khadas VIM and Khadas VIM2 boards) > > - signal resampling tuning with delay adjustments only (works fine for > > HS200 and UHS modes but doesn't fix HS400 eMMC chips, for example on > > Khadas VIM2) > > > > Further improvements for the HS400 mode are likely to be linked to the > > data strobe signal. > > Until we can figure out how to enable this mode safely and reliably, > > let's force it off. > > " > > Thanks for effort but all this just maintain the blur around HS400 on amlogic. > > Let me rephrase it: > Tuning (phase or resampling) is meant to compensate the clock round trip in UHS > and HS200 modes. In HS400, this should be taken care of by the data strobe. > But we have not been to enable this reliably enable this on amlogic chipset ... I wasn't aware of this: so far I assumed that we're not setting the phase correctly, end of the story. thank you again for taking your time to explain this! > ... and I believe we are back to the original commit message. no need to update the description just to explain how HS400 works in general, so feel free to use my: Acked-by: Martin Blumenstingl Martin