RE: [PATCH V4 2/2] PCI: rcar: Recalculate inbound range alignment for each controller entry

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: "marek.vasut@gmail.com" <marek.vasut@gmail.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	Marek Vasut <marek.vasut+renesas@gmail.com>,
	Andrew Murray <andrew.murray@arm.com>,
	Simon Horman <horms+renesas@verge.net.au>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Wolfram Sang <wsa@the-dreams.de>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>
Subject: RE: [PATCH V4 2/2] PCI: rcar: Recalculate inbound range alignment for each controller entry
Date: Tue, 29 Oct 2019 11:12:32 +0000	[thread overview]
Message-ID: <TYAPR01MB45442DBF6F1308E693DC2274D8610@TYAPR01MB4544.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <20191029103452.GA27171@e121166-lin.cambridge.arm.com>

Hi Lorenzo,

> From: Lorenzo Pieralisi, Sent: Tuesday, October 29, 2019 7:35 PM
> 
> On Tue, Oct 29, 2019 at 01:18:04AM +0000, Yoshihiro Shimoda wrote:
> > Hi Lorenzo,
> >
> > > From: Lorenzo Pieralisi, Sent: Monday, October 28, 2019 7:21 PM
> > >
> > > On Mon, Oct 28, 2019 at 08:35:32AM +0000, Yoshihiro Shimoda wrote:
> > > > Hi Marek-san.
> > > >
> > > > > From: Marek Vasut, Sent: Sunday, October 27, 2019 3:27 AM
> > > > >
> > > > > Due to hardware constraints, the size of each inbound range entry
> > > > > populated into the controller cannot be larger than the alignment
> > > > > of the entry's start address. Currently, the alignment for each
> > > > > "dma-ranges" inbound range is calculated only once for each range
> > > > > and the increment for programming the controller is also derived
> > > > > from it only once. Thus, a "dma-ranges" entry describing a memory
> > > > > at 0x48000000 and size 0x38000000 would lead to multiple controller
> > > > > entries, each 0x08000000 long.
> > > >
> > > > I added a debug code [1] and I confirmed that each entry is not 0x08000000 long [2].
> > > >
> > > > After fixed the commit log above,
> > >
> > > So what does this mean in practice ? Does it mean that the commit log is
> > > wrong or that the issue is not present as described, in the mainline
> > > code ?
> >
> > I meant the commit log is wrong. In such the case, the multiple controller
> > entries has 3 kind of size like below.
> 
> OK, that's confusing. The commit log is describing the issue it is
> fixing and you are reporting that's not what happens in practice, so in
> short my question is, is it possible to describe the issue you
> are fixing with an example representative of what's happening and
> explaining why we need to apply this patch please ?

I'm very sorry, I completely misunderstood the original commit description.
I misunderstood "each 0x08000000 log" was a behavior of after we applied
this patch...

So, the description is no problem. In other words, we don't need to fix
any description on this patch.

Best regards,
Yoshihiro Shimoda