From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aapo Vienamo Subject: Re: [PATCH v2 25/40] mmc: sdhci: Add a quirk to disable card clock during tuning Date: Tue, 28 Aug 2018 18:41:29 +0300 Message-ID: <20180828184129.525439ba@dhcp-10-21-25-168> References: <1533924522-1037-1-git-send-email-avienamo@nvidia.com> <1533924522-1037-26-git-send-email-avienamo@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Adrian Hunter Cc: Rob Herring , Mark Rutland , Thierry Reding , Jonathan Hunter , Ulf Hansson , Mikko Perttunen , Stefan Agner , devicetree@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org List-Id: devicetree@vger.kernel.org On Mon, 27 Aug 2018 14:25:44 +0300 Adrian Hunter wrote: > On 10/08/18 21:08, Aapo Vienamo wrote: > > Add a quirk to disable card clock when the tuning command is sent. > > > > This has to be done to prevent the SDHCI controller from hanging on > > Tegra210. Without the quirk enabled there appears to be around 10% > > chance that the tuning sequence will fail and time out due to the > > controller locking up. > > > > Signed-off-by: Aapo Vienamo > > --- > > drivers/mmc/host/sdhci.c | 15 +++++++++++++++ > > drivers/mmc/host/sdhci.h | 2 ++ > > 2 files changed, 17 insertions(+) > > > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c > > index 04dc443..166b16f 100644 > > --- a/drivers/mmc/host/sdhci.c > > +++ b/drivers/mmc/host/sdhci.c > > @@ -2175,6 +2175,7 @@ static void sdhci_send_tuning(struct sdhci_host *host, u32 opcode) > > struct mmc_request mrq = {}; > > unsigned long flags; > > u32 b = host->sdma_boundary; > > + u16 clk; > > > > spin_lock_irqsave(&host->lock, flags); > > > > @@ -2183,6 +2184,13 @@ static void sdhci_send_tuning(struct sdhci_host *host, u32 opcode) > > cmd.mrq = &mrq; > > > > mrq.cmd = &cmd; > > + > > + if (host->quirks2 & SDHCI_QUIRK2_TUNE_DIS_CARD_CLK) { > > + clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL); > > + clk &= ~SDHCI_CLOCK_CARD_EN; > > + sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL); > > Rather than using a quirk, could you use the sdhci I/O accessors to disable > the clock before the tuning comment is written, udelay(1), and then enable > it again? This was the way it was implemented in the downstream kernel. However, doing it in the IO accessor when a tuning command is sent seems to work too. -Aapo