linux-kernel - Re: [PATCH V2] PCI: dwc: Fix n

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Message-ID: <CAPOBaE68E6T3X96rvW5UdGb82LmAKKRuZ=Fb0SwgdLY7Px4ohw@mail.gmail.com>
Date:   Thu, 29 Sep 2022 09:49:50 -0700
From:   Han Jingoo <jingoohan1@...il.com>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     gustavo.pimentel@...opsys.com, lpieralisi@...nel.org,
        robh@...nel.org, kw@...ux.com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        kthota@...dia.com, mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V2] PCI: dwc: Fix n_fts[] array overrun

On Wed, Sep 28, 2022 Vidya Sagar <vidyas@...dia.com> wrote:

> On 9/29/2022 7:34 AM, Han Jingoo wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Mon, Sep 26, 2022, Vidya Sagar <vidyas@...dia.com> wrote:
> >>
> >> commit aeaa0bfe89654 ("PCI: dwc: Move N_FTS setup to common setup")
> >> incorrectly uses pci->link_gen in deriving the index to the
> >> n_fts[] array also introducing the issue of accessing beyond the
> >> boundaries of array for greater than Gen-2 speeds. This change fixes
> >> that issue.
> >
> > Dear Vidya,
> >
> > I am just ok with this patch. By the way, do we need another patch to generalize
> > this setting? Currently, this code targets only Gen1 and Gen2. But, in
> > my opinion,
> > it is possible that this driver can be  used for more than Gen2,
> > later. PCIe Gen6
> > standard is available and Synopsys has their solution for Gen6. So, would you
> > send a new patch to generalize this thing, later?
> > Thank you.
>
> As I mentioned in the commit message, current code is incorrectly using
> 'gen' in the index and ideally n_fts programming has nothing to do with
> the speed and hence I tried to remove the 'gen' reference in the current
> patch. So, the same code (after applying this patch) should work for any
> future Synopsys IP versions supporting higher speeds.

I see. Thank you for your confirmation.

Best regards,
Jingoo Han

>
> Thanks,
> Vidya Sagar
>
> >
> > Best regards,
> > Jingoo Han
> >
> >>
> >> Fixes: aeaa0bfe8965 ("PCI: dwc: Move N_FTS setup to common setup")
> >> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> >> Acked-by: Jingoo Han <jingoohan1@...il.com>
> >> ---
> >> V2:
> >> * Addressed review comments from Bjorn
> >> * Added "Acked-by: Jingoo Han <jingoohan1@...il.com>"
> >>
> >>   drivers/pci/controller/dwc/pcie-designware.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> >> index 650a7f22f9d0..3df687667f27 100644
> >> --- a/drivers/pci/controller/dwc/pcie-designware.c
> >> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> >> @@ -649,7 +649,7 @@ void dw_pcie_setup(struct dw_pcie *pci)
> >>          if (pci->n_fts[1]) {
> >>                  val = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
> >>                  val &= ~PORT_LOGIC_N_FTS_MASK;
> >> -               val |= pci->n_fts[pci->link_gen - 1];
> >> +               val |= pci->n_fts[1];
> >>                  dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> >>          }
> >>
> >> --
> >> 2.17.1
> >>