linux-kernel - Re: [PATCH v5 05/12] PCI: brcmstb: Use swinit reset if available

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Message-ID: <CA+-6iNys9hW6O=kYE0qSgny6zviKmQkn6hNnpL+-9s4oYPOWuw@mail.gmail.com>
Date: Mon, 12 Aug 2024 13:54:59 -0400
From: Jim Quinlan <james.quinlan@...adcom.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: linux-pci@...r.kernel.org, Nicolas Saenz Julienne <nsaenz@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, 
	Cyril Brulebois <kibi@...ian.org>, Stanimir Varbanov <svarbanov@...e.de>, 
	Krzysztof Kozlowski <krzk@...nel.org>, bcm-kernel-feedback-list@...adcom.com, 
	jim2101024@...il.com, Florian Fainelli <florian.fainelli@...adcom.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>, 
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-rpi-kernel@...ts.infradead.org>, 
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>, 
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 05/12] PCI: brcmstb: Use swinit reset if available

On Tue, Aug 6, 2024 at 11:03 PM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
>
> On Wed, Jul 31, 2024 at 06:28:19PM -0400, Jim Quinlan wrote:
> > The 7712 SOC adds a software init reset device for the PCIe HW.
> > If found in the DT node, use it.
> >
> > Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
> > ---
> >  drivers/pci/controller/pcie-brcmstb.c | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > index 4d68fe318178..948fd4d176bc 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -266,6 +266,7 @@ struct brcm_pcie {
> >       struct reset_control    *rescal;
> >       struct reset_control    *perst_reset;
> >       struct reset_control    *bridge_reset;
> > +     struct reset_control    *swinit_reset;
> >       int                     num_memc;
> >       u64                     memc_size[PCIE_BRCM_MAX_MEMC];
> >       u32                     hw_rev;
> > @@ -1633,12 +1634,30 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> >       if (IS_ERR(pcie->bridge_reset))
> >               return PTR_ERR(pcie->bridge_reset);
> >
> > +     pcie->swinit_reset = devm_reset_control_get_optional_exclusive(&pdev->dev, "swinit");
> > +     if (IS_ERR(pcie->swinit_reset))
> > +             return PTR_ERR(pcie->swinit_reset);
> > +
> >       ret = clk_prepare_enable(pcie->clk);
> >       if (ret)
> >               return dev_err_probe(&pdev->dev, ret, "could not enable clock\n");
> >
> >       pcie->bridge_sw_init_set(pcie, 0);
> >
> > +     if (pcie->swinit_reset) {
>
> You already have a callback called 'bridge_sw_init_set', so this 'swinit_reset'
> is different from 'bridge_sw_init'?
Yes.  The swinit_reset is a soft reset of the entire core while
bridge_sw_init reset is only for the bridge to system memory.

If so, does it make sense to move this into
> the callback itself to have all reset sequence in one place?

The order and placement of the resets can sometimes be fragile and I
would prefer to leave them where they are.

Regards,
Jim Quinlan
Broadcom STB/CM

>
> - Mani
>
> > +             ret = reset_control_assert(pcie->swinit_reset);
> > +             if (dev_err_probe(&pdev->dev, ret, "could not assert reset 'swinit'\n"))
> > +                     goto clk_disable_unprepare;
> > +
> > +             /* HW team recommends 1us for proper sync and propagation of reset */
> > +             udelay(1);
> > +
> > +             ret = reset_control_deassert(pcie->swinit_reset);
> > +             if (dev_err_probe(&pdev->dev, ret,
> > +                               "could not de-assert reset 'swinit' after asserting\n"))
> > +                     goto clk_disable_unprepare;
> > +     }
> > +
> >       ret = reset_control_reset(pcie->rescal);
> >       if (dev_err_probe(&pdev->dev, ret, "failed to deassert 'rescal'\n"))
> >               goto clk_disable_unprepare;
> > --
> > 2.17.1
> >
>
> --
> மணிவண்ணன் சதாசிவம்

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