From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44EC65C9C; Wed, 27 Dec 2023 06:13:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Nce85qwp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03545C433C7; Wed, 27 Dec 2023 06:13:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1703657608; bh=Z0HbVb39Y0GB2FLNaCZrOecrN2XrOMtaehWwhJhRtMU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Nce85qwpQaLfStbrawAERY3lGpL3rAELIEEpHODCWbcxS+D6YjB4p/mUoaSOkVGhQ jy8D3k2+pLkOMRPp1IuVlRl8fESpdS9IGPr8a6a7w1N3JkKWUuHz6N4uLf1sa9oT1z CdIQY1lOqYXJGNzpLKesLSJVXlOX5fKvPofPLs/El6iwZBpj8TCSIuV301TfxlKbdv R9Q6MI1nbg+iLIGfGdiEUv6C8qp68prE49Q11z2PNv4sSCHatToBlcU23nwodqbeTW Cu5Y+GZD3rWhdHLwmTLulCbE/ZaBQigCYiLzNFUeVfKi570cc63Ng+AGDjjXzGjfA6 7OtB08tZVBdBw== Date: Wed, 27 Dec 2023 11:43:17 +0530 From: Manivannan Sadhasivam To: Andrew Halaney Cc: Andy Gross , Bjorn Andersson , Konrad Dybcio , "James E.J. Bottomley" , "Martin K. Petersen" , Yaniv Gardi , Dov Levenglick , Hannes Reinecke , Subhash Jadavani , Gilad Broner , Venkat Gopalakrishnan , Janek Kotas , Alim Akhtar , Avri Altman , Bart Van Assche , Anjana Hari , Dolev Raviv , Can Guo , Will Deacon , linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC v2 08/11] scsi: ufs: core: Perform read back after disabling interrupts Message-ID: <20231227061317.GF2814@thinkpad> References: <20231221-ufs-reset-ensure-effect-before-delay-v2-0-75af2a9bae51@redhat.com> <20231221-ufs-reset-ensure-effect-before-delay-v2-8-75af2a9bae51@redhat.com> Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20231221-ufs-reset-ensure-effect-before-delay-v2-8-75af2a9bae51@redhat.com> On Thu, Dec 21, 2023 at 12:25:25PM -0600, Andrew Halaney wrote: > Currently, interrupts are cleared and disabled prior to registering the > interrupt. An mb() is used to complete the clear/disable writes before > the interrupt is registered. > > mb() ensure that the write completes, but completion doesn't mean that > it isn't stored in a buffer somewhere. The recommendation for > ensuring these bits have taken effect on the device is to perform a read > back to force it to make it all the way to the device. This is > documented in device-io.rst and a talk by Will Deacon on this can > be seen over here: > > https://youtu.be/i6DayghhA8Q?si=MiyxB5cKJXSaoc01&t=1678 > > Let's do that to ensure these bits hit the device. Because the mb()'s > purpose wasn't to add extra ordering (on top of the ordering guaranteed > by writel()/readl()), it can safely be removed. > > Fixes: 199ef13cac7d ("scsi: ufs: avoid spurious UFS host controller interrupts") > Signed-off-by: Andrew Halaney Same comment as patch 07/11. Reviewed-by: Manivannan Sadhasivam - Mani > --- > drivers/ufs/core/ufshcd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c > index 7bfb556e5b8e..bb603769b029 100644 > --- a/drivers/ufs/core/ufshcd.c > +++ b/drivers/ufs/core/ufshcd.c > @@ -10568,7 +10568,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq) > * Make sure that UFS interrupts are disabled and any pending interrupt > * status is cleared before registering UFS interrupt handler. > */ > - mb(); > + ufshcd_readl(hba, REG_INTERRUPT_ENABLE); > > /* IRQ registration */ > err = devm_request_irq(dev, irq, ufshcd_intr, IRQF_SHARED, UFSHCD, hba); > > -- > 2.43.0 > -- மணிவண்ணன் சதாசிவம்