Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:3 as permitted sender) client-ip=2620:137:e000::3:3;
Feedback-ID: i56a14606:Fastmail
User-Agent: Cyrus-JMAP/3.9.0-alpha0-1048-g9229b632c5-fm-20231019.001-g9229b632
MIME-Version: 1.0
Message-Id: <7acec62a-6b5c-4635-b486-ceadee279f35@app.fastmail.com>
In-Reply-To: <415ae047-0c9e-1e85-f4ff-e17a63aa0dfc@amd.com>
References: <20231023160539.1537355-1-arnd@kernel.org>
 <20231023160539.1537355-2-arnd@kernel.org>
 <78427021-ddc0-45b6-a16b-bf8bc8f84003@app.fastmail.com>
 <415ae047-0c9e-1e85-f4ff-e17a63aa0dfc@amd.com>
Date:   Fri, 27 Oct 2023 15:29:34 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Lizhi Hou" <lizhi.hou@amd.com>, "Arnd Bergmann" <arnd@kernel.org>,
        "Martin Tuma" <martin.tuma@digiteqautomotive.com>,
        "Mauro Carvalho Chehab" <mchehab@kernel.org>,
        "Hans Verkuil" <hverkuil-cisco@xs4all.nl>,
        dmaengine@vger.kernel.org, "Brian Xu" <brian.xu@amd.com>,
        "Raj Kumar Rampelli" <raj.kumar.rampelli@amd.com>,
        "Vinod Koul" <vkoul@kernel.org>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] media: pci: mgb4: remove bogus 'select' statements
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, Oct 24, 2023, at 18:18, Lizhi Hou wrote:
> On 10/24/23 06:27, Arnd Bergmann wrote:
>> On Mon, Oct 23, 2023, at 18:05, Arnd Bergmann wrote:
>>
>> aarch64-linux-ld: drivers/media/pci/mgb4/mgb4_core.o: in function `in=
it_i2c': mgb4_core.c:(.text+0x3ec): undefined reference to `xdma_get_use=
r_irq'
>> aarch64-linux-ld: mgb4_core.c:(.text+0x404): undefined reference to `=
xdma_enable_user_irq'
>>
>> I couldn't easily figure out what a 'user_irq' is here,
>> but I wonder if this is the expected way to use the DMA engine
>> layer. Maybe this should have been a nested irqchip instead,
>> or it should be encoded in the DMA request specifier?
>
> Hi Arnd,
>
> Here is a brief description of 'user_irq' and 'xdma_enable_user_irq'
>
> The XDMA subsystem is used in conjunction with the PCIe IP block. Plea=
se=20
> see https://lwn.net/Articles/911496/ for the overall information.
>
> XDMA can forward PCIe msi-x interrupt to/from user logic hardware (e.g=
.=20
> Digiteq device) which is connected to its user irq pin.=C2=A0 And XDMA=
 has a=20
> register to enable/disabe interrupt forwarding for a specific user irq=
 pin.
>
> 'xdma_enable_user_irq' and 'xdma_disable_user_irq' are provided for=20
> hardware driver which is designed to use XDMA to enable/disable its=20
> interrupt. And based on the previous discussion with Mark, Digiteq=20
> device does not use its own register to enable/disable interrupt but=20
> relies on XDMA.=C2=A0 Please see=20
> https://lore.kernel.org/lkml/daccee4a-ac3c-bfc1-4876-24e6ecf5bcf1@gpxs=
ee.org/

Ok, in this case, I would suggest using 'depends on XILINX_XDMA'
instead of the 'select' statement. I'll send a v2.

     Arnd