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From: Christoph Hellwig <hch@infradead.org>
To: Alexander Lobakin <alexandr.lobakin@intel.com>
Cc: 이왕석 <wangseok.lee@samsung.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	"jingoohan1@gmail.com" <jingoohan1@gmail.com>,
	"gustavo.pimentel@synopsys.com" <gustavo.pimentel@synopsys.com>,
	"lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
	"robh@kernel.org" <robh@kernel.org>,
	"kw@linux.com" <kw@linux.com>,
	"bhelgaas@google.com" <bhelgaas@google.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"jesper.nilsson@axis.com" <jesper.nilsson@axis.com>,
	"vkoul@kernel.org" <vkoul@kernel.org>,
	"kernel@axis.com" <kernel@axis.com>, 전문기 <moonki.jun@samsung.com>
Subject: Re: [PATCH] PCI: dwc: Modify the check about MSI DMA mask 32-bit
Date: Wed, 30 Mar 2022 08:45:31 -0700	[thread overview]
Message-ID: <YkR7G/V8E+NKBA2h@infradead.org> (raw)
In-Reply-To: <20220330093526.2728238-1-alexandr.lobakin@intel.com>

On Wed, Mar 30, 2022 at 11:35:26AM +0200, Alexander Lobakin wrote:
> I'm not super familiar with the DMA internals, so adding Chris here,
> maybe he'd like to comment, but anyway, the lower/arch layer must
> not give the DMA addresses wider than the number of bits passed to
> dma_set_mask() if that call returned 0.

So, the basic assumption in the kernel is that 32-bit DMA is always
supported, and dma_set_maks for that should not fail.  If the
system (or root port, internal interconnect) supports less than that
we'll bounce buffer.  But how and why would you hand out addresses
larger than that?  It really is not valid, but I can't even see how
it could happen.

  reply	other threads:[~2022-03-30 15:45 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20220328023009epcms2p309a5dfc2ff29d0a9945f65799963193c@epcms2p3>
2022-03-28  2:30 ` [PATCH] PCI: dwc: Modify the check about MSI DMA mask 32-bit 이왕석
2022-03-28 14:32   ` Alexander Lobakin
     [not found]   ` <CGME20220328143454epcas2p27a340d09e9f4e74af1eaa44559e372a5@epcms2p8>
2022-03-30  3:52     ` 이왕석
2022-03-30  9:35       ` Alexander Lobakin
2022-03-30 15:45         ` Christoph Hellwig [this message]
     [not found]         ` <CGME20220328143454epcas2p27a340d09e9f4e74af1eaa44559e372a5@epcms2p7>
2022-03-31  5:34           ` 이왕석
2022-04-08  5:32           ` Wangseok Lee
2022-04-08  5:39             ` Christoph Hellwig
2022-04-08 15:47             ` Lorenzo Pieralisi
     [not found]             ` <CGME20220328143454epcas2p27a340d09e9f4e74af1eaa44559e372a5@epcms2p5>
2022-04-11  6:59               ` Wangseok Lee
2022-04-11  7:10                 ` Christoph Hellwig
     [not found]                 ` <CGME20220328143454epcas2p27a340d09e9f4e74af1eaa44559e372a5@epcms2p1>
2022-04-11  9:47                   ` Wangseok Lee
2022-04-11 12:54                     ` Christoph Hellwig
2022-04-13 11:54                       ` Robin Murphy
2022-04-18  3:12                   ` Wangseok Lee
     [not found]         ` <CGME20220328143454epcas2p27a340d09e9f4e74af1eaa44559e372a5@epcms2p4>
2022-04-08  2:34           ` Wangseok Lee
2022-04-08  5:06             ` Christoph Hellwig

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