linux-kernel - Re: [PATCH v6 1/3] of/pci/dma: fix DMA configuration for PCI masters

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Message-ID: <20170517171016.GE31462@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 17 May 2017 12:10:16 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Oza Pawandeep <oza.oza@...adcom.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        Oza Pawandeep <oza.pawandeep@...il.com>
Subject: Re: [PATCH v6 1/3] of/pci/dma: fix DMA configuration for PCI masters

On Tue, May 16, 2017 at 10:52:05AM +0530, Oza Pawandeep wrote:
> current device framework and OF framework integration assumes

s/current/The current/

> dma-ranges in a way where memory-mapped devices define their
> dma-ranges. (child-bus-address, parent-bus-address, length).
> 
> of_dma_configure is specifically written to take care of memory
> mapped devices. but no implementation exists for pci to take
> care of pcie based memory ranges.

s/pci/PCI/	(also other occurrences below)
s/pcie/PCIe/

I don't see how PCIe is relevant here.  The bridge might support PCIe,
but I don't think anything here is actually specific to PCIe.  If
that's the case, I think it's confusing to mention PCIe.

> for e.g. iproc based SOCs and other SOCs(suc as rcar) have PCI
> world dma-ranges.
> dma-ranges = <0x43000000 0x00 0x00 0x00 0x00 0x80 0x00>;
> 
> this patch serves following:
> 
> 1) exposes interface to the pci host driver for their
> inbound memory ranges
> 
> 2) provide an interface to callers such as of_dma_get_ranges.
> so then the returned size get best possible (largest) dma_mask.
> because PCI RC drivers do not call APIs such as
> dma_set_coherent_mask() and hence rather it shows its addressing
> capabilities based on dma-ranges.
> for e.g.
> dma-ranges = <0x43000000 0x00 0x00 0x00 0x00 0x80 0x00>;
> we should get dev->coherent_dma_mask=0x7fffffffff.
> 
> 3) this patch handles multiple inbound windows and dma-ranges.
> it is left to the caller, how it wants to use them.
> the new function returns the resources in a standard and unform way
> 
> 4) this way the callers of for e.g. of_dma_get_ranges
> does not need to change.

Please start sentences with a capital letter.