From: Marc Zyngier <maz@kernel.org>
To: Manivannan Sadhasivam <mani@kernel.org>
Cc: "Jianjun Wang" <jianjun.wang@mediatek.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"AngeloGioacchino Del Regno"
<angelogioacchino.delregno@collabora.com>,
"Ryder Lee" <ryder.lee@mediatek.com>,
linux-pci@vger.kernel.org, linux-mediatek@lists.infradead.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, jieyy.yang@mediatek.com,
chuanjia.liu@mediatek.com, qizhong.cheng@mediatek.com,
jian.yang@mediatek.com, jianguo.zhang@mediatek.com
Subject: Re: [PATCH v2 1/3] PCI: mediatek: Allocate MSI address with dmam_alloc_coherent()
Date: Sun, 09 Jun 2024 13:32:38 +0100 [thread overview]
Message-ID: <864ja2l2jd.wl-maz@kernel.org> (raw)
In-Reply-To: <20240608090152.GB3282@thinkpad>
On Sat, 08 Jun 2024 10:01:52 +0100,
Manivannan Sadhasivam <mani@kernel.org> wrote:
>
> On Mon, Dec 11, 2023 at 04:52:54PM +0800, Jianjun Wang wrote:
> > Use dmam_alloc_coherent() to allocate the MSI address, instead of using
> > virt_to_phys().
> >
>
> What is the reason for this change? So now PCIE_MSI_VECTOR becomes unused?
More importantly, this is yet another example of the DW reference
driver nonsense, where memory is allocated for *MSI*, while the whole
point of MSIs is that it is a write that doesn't target memory, making
any form of RAM allocation absolutely pointless.
This silly approach has been cargo-culted for years, and while I
caught a few in my time, you can't beat copy-paste.
IMO, this patch is only making things worse instead of fixing things.
M.
--
Without deviation from the norm, progress is not possible.
WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Manivannan Sadhasivam <mani@kernel.org>
Cc: "Jianjun Wang" <jianjun.wang@mediatek.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"AngeloGioacchino Del Regno"
<angelogioacchino.delregno@collabora.com>,
"Ryder Lee" <ryder.lee@mediatek.com>,
linux-pci@vger.kernel.org, linux-mediatek@lists.infradead.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, jieyy.yang@mediatek.com,
chuanjia.liu@mediatek.com, qizhong.cheng@mediatek.com,
jian.yang@mediatek.com, jianguo.zhang@mediatek.com
Subject: Re: [PATCH v2 1/3] PCI: mediatek: Allocate MSI address with dmam_alloc_coherent()
Date: Sun, 09 Jun 2024 13:32:38 +0100 [thread overview]
Message-ID: <864ja2l2jd.wl-maz@kernel.org> (raw)
In-Reply-To: <20240608090152.GB3282@thinkpad>
On Sat, 08 Jun 2024 10:01:52 +0100,
Manivannan Sadhasivam <mani@kernel.org> wrote:
>
> On Mon, Dec 11, 2023 at 04:52:54PM +0800, Jianjun Wang wrote:
> > Use dmam_alloc_coherent() to allocate the MSI address, instead of using
> > virt_to_phys().
> >
>
> What is the reason for this change? So now PCIE_MSI_VECTOR becomes unused?
More importantly, this is yet another example of the DW reference
driver nonsense, where memory is allocated for *MSI*, while the whole
point of MSIs is that it is a write that doesn't target memory, making
any form of RAM allocation absolutely pointless.
This silly approach has been cargo-culted for years, and while I
caught a few in my time, you can't beat copy-paste.
IMO, this patch is only making things worse instead of fixing things.
M.
--
Without deviation from the norm, progress is not possible.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2024-06-09 12:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-11 8:52 [PATCH v2 0/3] PCI: mediatek: Allocate MSI address with dmam_alloc_coherent() Jianjun Wang
2023-12-11 8:52 ` Jianjun Wang
2023-12-11 8:52 ` [PATCH v2 1/3] " Jianjun Wang
2023-12-11 8:52 ` Jianjun Wang
2024-06-08 9:01 ` Manivannan Sadhasivam
2024-06-08 9:01 ` Manivannan Sadhasivam
2024-06-09 12:32 ` Marc Zyngier [this message]
2024-06-09 12:32 ` Marc Zyngier
2024-06-11 17:21 ` Bjorn Helgaas
2023-12-11 8:52 ` [PATCH v2 2/3] PCI: mediatek-gen3: Do not break probe flow when MSI init fails Jianjun Wang
2023-12-11 8:52 ` Jianjun Wang
2023-12-11 8:52 ` [PATCH v2 3/3] PCI: mediatek-gen3: Allocate MSI address with dmam_alloc_coherent() Jianjun Wang
2023-12-11 8:52 ` Jianjun Wang
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