linux-kernel - Re: [PATCH] PCI: qcom: configure the parf halt window size to 1GB

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Date:   Mon, 10 Jul 2023 08:52:02 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Devi Priya <quic_devipriy@...cinc.com>
Cc:     Manivannan Sadhasivam <mani@...nel.org>, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org,
        lpieralisi@...nel.org, kw@...ux.com, robh@...nel.org,
        bhelgaas@...gle.com, linux-arm-msm@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_srichara@...cinc.com, quic_sjaganat@...cinc.com,
        quic_kathirav@...cinc.com, quic_anusha@...cinc.com,
        quic_ipkumar@...cinc.com
Subject: Re: [PATCH] PCI: qcom: configure the parf halt window size to 1GB

On Wed, Jul 05, 2023 at 03:57:13PM +0530, Devi Priya wrote:
> 
> 
> On 6/24/2023 11:53 AM, Manivannan Sadhasivam wrote:
> > On Fri, Jun 23, 2023 at 10:27:31AM +0530, Devi Priya wrote:
> > > Configure the ADDR_BIT_INDEX of PARF_AXI_MSTR_WR_ADDR_HALT_V2 register with
> > > 0x1E to increase the halt window size to 1GB so that, when new inbound
> > > posted write transactions whose address crosses 1G address range, the
> > > controller would halt all the incoming writes until all the previous AXI
> > > responses are received.
> > > 
> > 
> > Can you explain how the value of 0x1e corresponds to 1GB window size?
> 2^30 (0x1e) = 1G
> > 

So 0x1e selects 2^30 in the hardware? If so, please document it in the commit
message.

- Mani

> > > Signed-off-by: Devi Priya <quic_devipriy@...cinc.com>
> > > ---
> > >   This patch depends on the below series which adds support for PCIe
> > >   controllers in IPQ9574
> > >   https://lore.kernel.org/linux-arm-msm/20230519090219.15925-1-quic_devipriy@quicinc.com/
> > > 
> > >   drivers/pci/controller/dwc/pcie-qcom.c | 9 +++++++++
> > >   1 file changed, 9 insertions(+)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index c7579dfa5b1c..26c40e006120 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -116,6 +116,8 @@
> > >   /* PARF_AXI_MSTR_WR_ADDR_HALT register fields */
> > >   #define EN					BIT(31)
> > > +#define ADDR_BIT_INDEX				(BIT(0) | BIT(1) | BIT(2) | \
> > > +						BIT(3) | BIT(4) | BIT(5))
> > 
> > GENMASK(5, 0)
> okay
> > 
> > >   /* PARF_LTSSM register fields */
> > >   #define LTSSM_EN				BIT(8)
> > > @@ -154,6 +156,8 @@
> > >   #define QCOM_PCIE_CRC8_POLYNOMIAL		(BIT(2) | BIT(1) | BIT(0))
> > > +#define PARF_AXI_MSTR_WR_ADDR_HALT_WINDOW_SIZE	0x1e
> > 
> > GENMASK(4, 1) as these are address bits.
> okay
> 
> Thanks,
> Devi Priya
> > 
> > - Mani
> > 
> > > +
> > >   #define QCOM_PCIE_1_0_0_MAX_CLOCKS		4
> > >   struct qcom_pcie_resources_1_0_0 {
> > >   	struct clk_bulk_data clks[QCOM_PCIE_1_0_0_MAX_CLOCKS];
> > > @@ -1126,6 +1130,11 @@ static int qcom_pcie_post_init(struct qcom_pcie *pcie)
> > >   	writel(0, pcie->parf + PARF_Q2A_FLUSH);
> > > +	val = readl(pcie->parf + PARF_AXI_MSTR_WR_ADDR_HALT_V2);
> > > +	val &= ~ADDR_BIT_INDEX;
> > > +	writel(val | PARF_AXI_MSTR_WR_ADDR_HALT_WINDOW_SIZE, pcie->parf +
> > > +			PARF_AXI_MSTR_WR_ADDR_HALT_V2);
> > > +
> > >   	dw_pcie_dbi_ro_wr_en(pci);
> > >   	writel(PCIE_CAP_SLOT_VAL, pci->dbi_base + offset + PCI_EXP_SLTCAP);
> > > -- 
> > > 2.17.1
> > > 
> > 

-- 
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