linux-kernel - Re: [PATCH v2 2/8] PCI: qcom: Disable write access to read only registers for IP v2.9.0

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Message-ID: <20230529085512.GB5633@thinkpad>
Date:   Mon, 29 May 2023 14:25:12 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        kw@...ux.com, bhelgaas@...gle.com, robh@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, steev@...i.org,
        quic_srichara@...cinc.com, dmitry.baryshkov@...aro.org,
        Dmitry Baryshkov <dmitry.baryshkov@...il.com>
Subject: Re: [PATCH v2 2/8] PCI: qcom: Disable write access to read only
 registers for IP v2.9.0

On Mon, May 22, 2023 at 10:56:19AM +0200, Lorenzo Pieralisi wrote:
> On Fri, May 19, 2023 at 08:01:11PM +0530, Manivannan Sadhasivam wrote:
> > In the post init sequence of v2.9.0, write access to read only registers
> > are not disabled after updating the registers. Fix it by disabling the
> > access after register update.
> > 
> > Fixes: 0cf7c2efe8ac ("PCI: qcom: Add IPQ60xx support")
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...il.com>
> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index 01795ee7ce45..391a45d1e70a 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -1136,6 +1136,7 @@ static int qcom_pcie_post_init_2_9_0(struct qcom_pcie *pcie)
> >  	writel(0, pcie->parf + PARF_Q2A_FLUSH);
> >  
> >  	dw_pcie_dbi_ro_wr_en(pci);
> > +
> 
> Nit: spurious change.
> 

Well that's intentional. It's good to have a newline between these guard
functions to differentiate them from the DBI accesses. We do it in other places
in the driver.

But I thought this change doesn't warrant a mention in commit message or a
separate patch.

Let me know otherwise.

- Mani

> Lorenzo
> 
> >  	writel(PCIE_CAP_SLOT_VAL, pci->dbi_base + offset + PCI_EXP_SLTCAP);
> >  
> >  	val = readl(pci->dbi_base + offset + PCI_EXP_LNKCAP);
> > @@ -1145,6 +1146,8 @@ static int qcom_pcie_post_init_2_9_0(struct qcom_pcie *pcie)
> >  	writel(PCI_EXP_DEVCTL2_COMP_TMOUT_DIS, pci->dbi_base + offset +
> >  			PCI_EXP_DEVCTL2);
> >  
> > +	dw_pcie_dbi_ro_wr_dis(pci);
> > +
> >  	for (i = 0; i < 256; i++)
> >  		writel(0, pcie->parf + PARF_BDF_TO_SID_TABLE_N + (4 * i));
> >  
> > -- 
> > 2.25.1
> > 

-- 
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