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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qqFDl-00Dk4D-0X; Tue, 10 Oct 2023 16:04:33 +0000 Received: from ams.source.kernel.org ([2604:1380:4601:e00::1]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qqFDg-00Dk3S-1S; Tue, 10 Oct 2023 16:04:31 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by ams.source.kernel.org (Postfix) with ESMTP id 4B66EB81CD9; Tue, 10 Oct 2023 16:04:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66636C433C9; Tue, 10 Oct 2023 16:04:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696953865; bh=CPjakDH/b/NnLZYhG6qAlFTOBENXy2ZPobzsoGHhlUE=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=oKoB9O5WH9REfKO57RoBNap5FlOCwlHa5tWCMjXkqpZGOdyHCWTAd/nvxQGrRbScf RmwSZew+Hu9gAxh/XrnU6Gya5EylyR2BhX5LJfw9MiSoYPYbFPfmQJRa4vmK1LIcK4 fxKkbPA6DLOwewexCElKjkUTlw9mGdpspzauxvuSpU6QPr1TyBnR/bahgwJ5YaHJ1j hNeS5F5I498tCazwxNI4y89y8FYggplvKSaAf7OHXnl3X7QF1pUA7Bd+o2pXlPMrZr fXQlXzmmPEzoenCDb3Mtcx8FCJTO8Ouz8pa8WSGpx3WZqQ7uI1YNZfUMsnC82m26/x +zK+IfiHqRekg== Date: Tue, 10 Oct 2023 11:04:23 -0500 From: Bjorn Helgaas To: Daniel Golle Cc: linux-pci@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, AngeloGioacchino Del Regno , Matthias Brugger , Bjorn Helgaas , Rob Herring , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Lorenzo Pieralisi , Jianjun Wang , Ryder Lee , Christian Marangi , Frank Wunderlich , John Crispin Subject: Re: [PATCH] PCI: mediatek-gen3: fix PCIe #PERST being de-asserted too early Message-ID: <20231010160423.GA977719@bhelgaas> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231010_090428_788862_77E5D879 X-CRM114-Status: GOOD ( 23.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Oct 06, 2023 at 09:45:58AM +0200, Daniel Golle wrote: > The driver for MediaTek gen3 PCIe hosts de-asserts all reset > signals at the same time using a single register write operation. > Delay the de-assertion of the #PERST signal by 100ms as required by > PCIe CEM clause 2.2, some PCIe devices fail to come up otherwise. > > Signed-off-by: Daniel Golle > --- > drivers/pci/controller/pcie-mediatek-gen3.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c > index e0e27645fdf4..ba8cfce03aad 100644 > --- a/drivers/pci/controller/pcie-mediatek-gen3.c > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c > @@ -350,7 +350,13 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie) I feel like I'm missing something because this patch seems to be adding a delay for T_PVPERL, but the comment before the existing msleep() claims *it* is the T_PVPERL delay: * Described in PCIe CEM specification sections 2.2 (PERST# Signal) * and 2.2.1 (Initial Power-Up (G3 to S0)). * The deassertion of PERST# should be delayed 100ms (TPVPERL) * for the power and clock to become stable. > msleep(100); > > /* De-assert reset signals */ > - val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB); > + val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB); > + writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG); > + > + msleep(100); So I'm confused about these two sleeps. Are they for different parameters? T_PVPERL is defined from "Power stable to PERST# inactive". Do we have any actual indication of when to start that delay, i.e., do we have a clue about when power became stable? > + /* De-assert PERST# signals */ > + val &= ~(PCIE_PE_RSTB); > writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG); > > /* Check if the link is up or not */ > -- > 2.42.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel