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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hTjzJ-0004vA-4R; Thu, 23 May 2019 09:26:13 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hTjzG-0004uo-MD for linux-arm-kernel@lists.infradead.org; Thu, 23 May 2019 09:26:11 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 40E22341; Thu, 23 May 2019 02:26:10 -0700 (PDT) Received: from [10.1.197.61] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 920B33F718; Thu, 23 May 2019 02:26:03 -0700 (PDT) Subject: Re: [PATCH v4 01/10] ata: libahci: Ensure the host interrupt status bits are cleared To: raymond pang , Miquel Raynal References: <20190521143023.31810-1-miquel.raynal@bootlin.com> <20190521143023.31810-2-miquel.raynal@bootlin.com> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; 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Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190523_022610_732727_F3F0A437 X-CRM114-Status: GOOD ( 23.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Andrew Lunn , Baruch Siach , Jason Cooper , Nadav Haklai , devicetree@vger.kernel.org, Antoine Tenart , Gregory Clement , Maxime Chevallier , linux-ide@vger.kernel.org, Hans de Goede , Rob Herring , Jens Axboe , Thomas Petazzoni , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Sebastian Hesselbarth Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 23/05/2019 04:11, raymond pang wrote: > Hi Miquel, > > This patch adds clearing GHC.IS into hot path, could you explain how > irq storm is generated? thanks > According to AHCI Spec, HBA should not refer to GHC.IS to generate > MSI when applying multiple MSIs. Well spotted. I have the ugly feeling that this is because the Marvell AHCI implementation is not using MSIs at all, but instead a pair of wired interrupts (which are level triggered instead of edge, hence the screaming interrupts). The changes in the following patches abuse the rest of the driver by pretending this is a a multi-MSI setup, while it clearly doesn't match the expectation of the AHCI spec for MSIs. It looks like this shouldn't be imposed on other unsuspecting implementations which correctly use edge-triggered MSIs and do not require such an MMIO access. Thanks, M. > > Best Regards, > Raymond > > On Tue, May 21, 2019 at 2:31 PM Miquel Raynal wrote: >> >> ahci_multi_irqs_intr_hard() is going to be used as interrupt handler >> to support SATA per-port interrupts. The current logic is to check and >> clear the SATA port interrupt status register only. To avoid spurious >> IRQs and interrupt storms, it will be needed to clear the port >> interrupt bit in the host interrupt status register as well. >> >> Signed-off-by: Miquel Raynal >> --- >> drivers/ata/libahci.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c >> index 692782dddc0f..9db6f488db59 100644 >> --- a/drivers/ata/libahci.c >> +++ b/drivers/ata/libahci.c >> @@ -1912,7 +1912,10 @@ static void ahci_port_intr(struct ata_port *ap) >> static irqreturn_t ahci_multi_irqs_intr_hard(int irq, void *dev_instance) >> { >> struct ata_port *ap = dev_instance; >> + struct ata_host *host = ap->host; >> + struct ahci_host_priv *hpriv = host->private_data; >> void __iomem *port_mmio = ahci_port_base(ap); >> + void __iomem *mmio = hpriv->mmio; >> u32 status; >> >> VPRINTK("ENTER\n"); >> @@ -1924,6 +1927,8 @@ static irqreturn_t ahci_multi_irqs_intr_hard(int irq, void *dev_instance) >> ahci_handle_port_interrupt(ap, port_mmio, status); >> spin_unlock(ap->lock); >> >> + writel(BIT(ap->port_no), mmio + HOST_IRQ_STAT); >> + >> VPRINTK("EXIT\n"); >> >> return IRQ_HANDLED; >> -- >> 2.19.1 >> -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel