linux-kernel - Re: [PATCH v5 0/3] arm64: qcom: sa8775p: add cache coherency support for SA8775P

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Message-ID: <866ea7ee-54c3-4a89-981e-64d6d3b46497@linaro.org>
Date: Sat, 24 Feb 2024 11:19:27 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Mrinmay Sarkar <quic_msarkar@...cinc.com>, andersson@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 konrad.dybcio@...aro.org, manivannan.sadhasivam@...aro.org, robh@...nel.org
Cc: quic_shazhuss@...cinc.com, quic_nitegupt@...cinc.com,
 quic_ramkri@...cinc.com, quic_nayiluri@...cinc.com,
 dmitry.baryshkov@...aro.org, quic_krichai@...cinc.com,
 quic_vbadigan@...cinc.com, quic_schintav@...cinc.com,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 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 v5 0/3] arm64: qcom: sa8775p: add cache coherency support
 for SA8775P

On 23/02/2024 15:03, Mrinmay Sarkar wrote:
> 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 there no cache coherency issues exit
> 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.

Please confirm that your patchset passes 100% dtbs_check.

Best regards,
Krzysztof