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From: Kishon Vijay Abraham I <kishon@ti.com>
To: Alan Mikhak <alan.mikhak@sifive.com>,
	Haotian Wang <haotian.wang@sifive.com>, <haotian.wang@duke.edu>
Cc: "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
	"arnd@arndb.de" <arnd@arndb.de>,
	"jingoohan1@gmail.com" <jingoohan1@gmail.com>,
	Gustavo Pimentel <Gustavo.Pimentel@synopsys.com>,
	"palmer@sifive.com" <palmer@sifive.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Vinod Koul <vkoul@kernel.org>, "kjlu@umn.edu" <kjlu@umn.edu>,
	"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"bhelgaas@google.com" <bhelgaas@google.com>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"wen.yang99@zte.com.cn" <wen.yang99@zte.com.cn>
Subject: Re: [PATCH] PCI: endpoint: Add DMA to Linux PCI EP Framework
Date: Fri, 13 Sep 2019 17:41:23 +0530
Message-ID: <40fafe93-d2dd-b1f5-bc16-cd84ff07bd13@ti.com> (raw)
In-Reply-To: <CABEDWGx2N66L=27JY6Ywbfny78UaxENkxBTqxU37PfuQO-ZMZw@mail.gmail.com>

+ Haotian Wang

On 03/06/19 11:12 PM, Alan Mikhak wrote:
> On Sun, Jun 2, 2019 at 9:43 PM Kishon Vijay Abraham I <kishon@ti.com> wrote:
>> Hi Alan,
>> On 31/05/19 11:46 PM, Alan Mikhak wrote:
>>> On Thu, May 30, 2019 at 10:08 PM Kishon Vijay Abraham I <kishon@ti.com> wrote:
>>>> Hi Alan,
>>>>> Hi Kishon,
>>>>
>>>> I still have to look closer into your DMA patch but linked-list mode or single
>>>> block mode shouldn't be an user select-able option but should be determined by
>>>> the size of transfer.
>>>
>>> Please consider the following when taking a closer look at this patch.
>>
>> After seeing comments from Vinod and Arnd, it looks like the better way of
>> adding DMA support would be to register DMA within PCI endpoint controller to
>> DMA subsystem (as dmaengine) and use only dmaengine APIs in pci_epf_test.
> 
> Thanks Kishon. That makes it clear where these pieces should go.
> 
>>> In my specific use case, I need to verify that any valid block size,
>>> including a one byte transfer, can be transferred across the PCIe bus
>>> by memcpy_toio/fromio() or by DMA either as a single block or as
>>> linked-list. That is why, instead of deciding based on transfer size,
>>> this patch introduces the '-L' flag for pcitest to communicate the
>>> user intent across the PCIe bus to pci-epf-test so the endpoint can
>>> initiate the DMA transfer using a single block or in linked-list mode.
>> The -L option seems to select an internal DMA configuration which might be
>> specific to one implementation. As Gustavo already pointed, we should have only
>> generic options in pcitest. This would no longer be applicable when we move to
>> dmaengine.
> 
> Single-block DMA seemed as generic as linked-list DMA and
> memcpy_toio/fromio. It remains unclear how else to communicate that
> intent to pci_epf_test each time I invoke pcitest.
> 
> Regards,
> Alan
> 

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Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-23 22:24 Alan Mikhak
2019-05-24  8:59 ` Gustavo Pimentel
2019-05-24 19:42   ` Alan Mikhak
2019-05-27  9:09     ` Gustavo Pimentel
2019-05-29 22:37       ` Alan Mikhak
2019-05-30  5:46         ` Kishon Vijay Abraham I
2019-05-30 17:56           ` Alan Mikhak
2019-05-31  5:06             ` Kishon Vijay Abraham I
2019-05-31 18:16               ` Alan Mikhak
2019-06-03  4:41                 ` Kishon Vijay Abraham I
2019-06-03 17:42                   ` Alan Mikhak
2019-09-13 12:11                     ` Kishon Vijay Abraham I [this message]
2019-09-13 17:39                       ` Alan Mikhak
2019-05-31  5:07           ` Vinod Koul
2019-05-31  5:20             ` Kishon Vijay Abraham I
2019-05-31  6:32               ` Vinod Koul
2019-05-31  7:49                 ` Arnd Bergmann
2019-06-03  4:29                   ` Kishon Vijay Abraham I
2019-06-03  4:24                 ` Kishon Vijay Abraham I
2019-06-03  4:42                   ` Vinod Koul

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