linux-kernel - Re: [PATCH v6 2/3] PCI: qcom-ep: Override NO

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Message-ID: <20240310125700.GB3390@thinkpad>
Date: Sun, 10 Mar 2024 18:27:00 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Mrinmay Sarkar <quic_msarkar@...cinc.com>
Cc: andersson@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, konrad.dybcio@...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>,
	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 v6 2/3] PCI: qcom-ep: Override NO_SNOOP attribute for
 SA8775P EP

On Wed, Mar 06, 2024 at 06:41:11PM +0530, 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 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.
> 
> Signed-off-by: Mrinmay Sarkar <quic_msarkar@...cinc.com>

Same nit as previous patch. With that addressed,

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

> ---
>  drivers/pci/controller/dwc/pcie-qcom-ep.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> index 89d06a3..aa8e979 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> @@ -47,6 +47,7 @@
>  #define PARF_DBI_BASE_ADDR_HI			0x354
>  #define PARF_SLV_ADDR_SPACE_SIZE		0x358
>  #define PARF_SLV_ADDR_SPACE_SIZE_HI		0x35c
> +#define PARF_NO_SNOOP_OVERIDE			0x3d4
>  #define PARF_ATU_BASE_ADDR			0x634
>  #define PARF_ATU_BASE_ADDR_HI			0x638
>  #define PARF_SRIS_MODE				0x644
> @@ -86,6 +87,10 @@
>  #define PARF_DEBUG_INT_CFG_BUS_MASTER_EN	BIT(2)
>  #define PARF_DEBUG_INT_RADM_PM_TURNOFF		BIT(3)
>  
> +/* PARF_NO_SNOOP_OVERIDE register fields */
> +#define WR_NO_SNOOP_OVERIDE_EN                 BIT(1)
> +#define RD_NO_SNOOP_OVERIDE_EN                 BIT(3)
> +
>  /* PARF_DEVICE_TYPE register fields */
>  #define PARF_DEVICE_TYPE_EP			0x0
>  
> @@ -152,9 +157,11 @@ enum qcom_pcie_ep_link_status {
>  /**
>   * struct qcom_pcie_ep_cfg - Per SoC config struct
>   * @hdma_support: HDMA support on this SoC
> + * @override_no_snoop: Override NO_SNOOP attribute in TLP to enable cache snooping
>   */
>  struct qcom_pcie_ep_cfg {
>  	bool hdma_support;
> +	bool override_no_snoop;
>  };
>  
>  /**
> @@ -175,6 +182,7 @@ struct qcom_pcie_ep_cfg {
>   * @num_clks: PCIe clocks count
>   * @perst_en: Flag for PERST enable
>   * @perst_sep_en: Flag for PERST separation enable
> + * @cfg: PCIe EP config struct
>   * @link_status: PCIe Link status
>   * @global_irq: Qualcomm PCIe specific Global IRQ
>   * @perst_irq: PERST# IRQ
> @@ -202,6 +210,7 @@ struct qcom_pcie_ep {
>  	u32 perst_en;
>  	u32 perst_sep_en;
>  
> +	const struct qcom_pcie_ep_cfg *cfg;
>  	enum qcom_pcie_ep_link_status link_status;
>  	int global_irq;
>  	int perst_irq;
> @@ -497,6 +506,11 @@ static int qcom_pcie_perst_deassert(struct dw_pcie *pci)
>  	val |= BIT(8);
>  	writel_relaxed(val, pcie_ep->parf + PARF_LTSSM);
>  
> +	/* Override NO_SNOOP attribute in TLP to enable cache snooping */

Same comment as previous patch.

- Mani

> +	if (pcie_ep->cfg && pcie_ep->cfg->override_no_snoop)
> +		writel_relaxed(WR_NO_SNOOP_OVERIDE_EN | RD_NO_SNOOP_OVERIDE_EN,
> +				pcie_ep->parf + PARF_NO_SNOOP_OVERIDE);
> +
>  	return 0;
>  
>  err_disable_resources:
> @@ -811,7 +825,6 @@ static const struct dw_pcie_ep_ops pci_ep_ops = {
>  
>  static int qcom_pcie_ep_probe(struct platform_device *pdev)
>  {
> -	const struct qcom_pcie_ep_cfg *cfg;
>  	struct device *dev = &pdev->dev;
>  	struct qcom_pcie_ep *pcie_ep;
>  	char *name;
> @@ -826,8 +839,8 @@ static int qcom_pcie_ep_probe(struct platform_device *pdev)
>  	pcie_ep->pci.ep.ops = &pci_ep_ops;
>  	pcie_ep->pci.edma.nr_irqs = 1;
>  
> -	cfg = of_device_get_match_data(dev);
> -	if (cfg && cfg->hdma_support) {
> +	pcie_ep->cfg = of_device_get_match_data(dev);
> +	if (pcie_ep->cfg && pcie_ep->cfg->hdma_support) {
>  		pcie_ep->pci.edma.ll_wr_cnt = 8;
>  		pcie_ep->pci.edma.ll_rd_cnt = 8;
>  		pcie_ep->pci.edma.mf = EDMA_MF_HDMA_NATIVE;
> @@ -893,6 +906,7 @@ static void qcom_pcie_ep_remove(struct platform_device *pdev)
>  
>  static const struct qcom_pcie_ep_cfg cfg_1_34_0 = {
>  	.hdma_support = true,
> +	.override_no_snoop = true,
>  };
>  
>  static const struct of_device_id qcom_pcie_ep_match[] = {
> -- 
> 2.7.4
> 

-- 
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