linux-kernel - Re: [PATCH v7 0/3] arm64: qcom: sa8775p: add cache coherency support for SA8775P

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Message-ID: <20240517172058.GJ1947919@rocinante>
Date: Sat, 18 May 2024 02:20:58 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Mrinmay Sarkar <quic_msarkar@...cinc.com>
Cc: andersson@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, konrad.dybcio@...aro.org,
	manivannan.sadhasivam@...aro.org, robh@...nel.org,
	quic_shazhuss@...cinc.com, quic_nitegupt@...cinc.com,
	quic_ramkri@...cinc.com, quic_nayiluri@...cinc.com,
	quic_krichai@...cinc.com, quic_vbadigan@...cinc.com,
	quic_schintav@...cinc.com,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH v7 0/3] arm64: qcom: sa8775p: add cache coherency support
 for SA8775P

Hello,

> Due to some hardware changes, SA8775P has set the NO_SNOOP attribute
> in its TLP for all the PCIe controllers. NO_SNOOP attribute when set,
> the requester is indicating that no cache coherency issues exist for
> the addressed memory on the host i.e., memory is not cached. But in
> reality, requester cannot assume this unless there is a complete
> control/visibility over the addressed memory on the host.
> 
> And worst case, if the memory is cached on the host, it may lead to
> memory corruption issues. It should be noted that the caching of memory
> on the host is not solely dependent on the NO_SNOOP attribute in TLP.
> 
> So to avoid the corruption, this patch overrides the NO_SNOOP attribute
> by setting the PCIE_PARF_NO_SNOOP_OVERIDE register. This patch is not
> needed for other upstream supported platforms since they do not set
> NO_SNOOP attribute by default.
> 
> This series is to enable cache snooping logic in both RC and EP driver
> and add the "dma-coherent" property in dtsi to support cache coherency
> in SA8775P platform.
> 
> Dependency
> ----------
> 
> Depends on:
> https://lore.kernel.org/all/1701432377-16899-1-git-send-email-quic_msarkar@quicinc.com/
> https://lore.kernel.org/all/20240306-dw-hdma-v4-4-9fed506e95be@linaro.org/ [1]

Applied to qcom, thank you!

[01/02] PCI: qcom: Override NO_SNOOP attribute for SA8775P RC
        https://git.kernel.org/pci/pci/c/a51da87be9db
[02/02] PCI: qcom-ep: Override NO_SNOOP attribute for SA8775P EP
        https://git.kernel.org/pci/pci/c/ce38ead6a0ed

	Krzysztof