linux-kernel - Re: [PATCH v1 1/3] PCI: qcom: Enable cache coherency for SA8775P RC

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Date:   Thu, 2 Nov 2023 15:46:45 +0530
From:   Mrinmay Sarkar <quic_msarkar@...cinc.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>, <agross@...nel.org>,
        <andersson@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <mani@...nel.org>, <robh+dt@...nel.org>
CC:     <quic_shazhuss@...cinc.com>, <quic_nitegupt@...cinc.com>,
        <quic_ramkri@...cinc.com>, <quic_nayiluri@...cinc.com>,
        <dmitry.baryshkov@...aro.org>, <robh@...nel.org>,
        <quic_krichai@...cinc.com>, <quic_vbadigan@...cinc.com>,
        <quic_parass@...cinc.com>, <quic_schintav@...cinc.com>,
        <quic_shijjose@...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 v1 1/3] PCI: qcom: Enable cache coherency for SA8775P RC


On 10/31/2023 10:20 PM, Konrad Dybcio wrote:
> On 31.10.2023 16:46, Mrinmay Sarkar wrote:
>> This change will enable cache snooping logic to support
>> cache coherency for SA8755P RC platform.
> 8775
>
>> Signed-off-by: Mrinmay Sarkar <quic_msarkar@...cinc.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index 6902e97..6f240fc 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -51,6 +51,7 @@
>>   #define PARF_SID_OFFSET				0x234
>>   #define PARF_BDF_TRANSLATE_CFG			0x24c
>>   #define PARF_SLV_ADDR_SPACE_SIZE		0x358
>> +#define PCIE_PARF_NO_SNOOP_OVERIDE		0x3d4
>>   #define PARF_DEVICE_TYPE			0x1000
>>   #define PARF_BDF_TO_SID_TABLE_N			0x2000
>>   
>> @@ -117,6 +118,9 @@
>>   /* PARF_LTSSM register fields */
>>   #define LTSSM_EN				BIT(8)
>>   
>> +/* PARF_NO_SNOOP_OVERIDE register value */
> override
>> +#define NO_SNOOP_OVERIDE_EN			0xa
> is this actually some magic value and not BIT(1) | BIT(3)?
we need to set 1st and 3rd bit. yes, we can use BIT(1) | BIT(3).
>
>>   /* PARF_DEVICE_TYPE register fields */
>>   #define DEVICE_TYPE_RC				0x4
>>   
>> @@ -961,6 +965,13 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
>>   
>>   static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie)
>>   {
>> +	struct dw_pcie *pci = pcie->pci;
>> +	struct device *dev = pci->dev;
>> +
>> +	/* Enable cache snooping for SA8775P */
>> +	if (of_device_is_compatible(dev->of_node, "qcom,pcie-sa8775p"))
>> +		writel(NO_SNOOP_OVERIDE_EN, pcie->parf + PCIE_PARF_NO_SNOOP_OVERIDE);
> Why only for 8775 and not for other v2.7, or perhaps all other
> revisions?
yes this is only required for 8775 due to hw requirement we need to enable
cache snooping from the register level for 8775.
> Konrad
Thanks,
Mrinmay