Re: [PATCH 16/21] PCI: imx6: Allow probe deferral by reset GPIO

From: Andrey Smirnov <andrew.smirnov@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Barebox List <barebox@lists.infradead.org>
Subject: Re: [PATCH 16/21] PCI: imx6: Allow probe deferral by reset GPIO
Date: Fri, 11 Jan 2019 20:24:10 -0800	[thread overview]
Message-ID: <CAHQ1cqGikVYzaTvzOTpbEr9G7S_k9EevbmTTPX3EsCwFR0totw@mail.gmail.com> (raw)
In-Reply-To: <20190110080519.plzbkseqs3ndn3s6@pengutronix.de>

On Thu, Jan 10, 2019 at 12:05 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
>
> On Tue, Jan 08, 2019 at 11:12:05PM -0800, Andrey Smirnov wrote:
> > Port of a Linux commit bde4a5a00e761f55be92f62378cf5024ced79ee3
> >
> >   Some designs implement reset GPIO via a GPIO expander connected to a
> >   peripheral bus.  One such example would be i.MX7 Sabre board where said
> >   GPIO is provided by SPI shift register connected to a bitbanged SPI bus.
> >   To support such designs, allow reset GPIO request to defer probing of the
> >   driver.
> >
> >   Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> >   Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> >   Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
> >   Cc: yurovsky@gmail.com
> >   Cc: Fabio Estevam <fabio.estevam@nxp.com>
> >   Cc: Dong Aisheng <dongas86@gmail.com>
> >   Cc: linux-arm-kernel@lists.infradead.org
> >
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> > ---
> >  drivers/pci/pci-imx6.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/pci-imx6.c b/drivers/pci/pci-imx6.c
> > index 6471f95b6..517c6bef8 100644
> > --- a/drivers/pci/pci-imx6.c
> > +++ b/drivers/pci/pci-imx6.c
> > @@ -562,8 +562,8 @@ static const struct dw_pcie_host_ops imx6_pcie_host_ops = {
> >       .host_init = imx6_pcie_host_init,
> >  };
> >
> > -static int __init imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
> > -                                  struct device_d *dev)
> > +static int imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
> > +                           struct device_d *dev)
> >  {
> >       struct dw_pcie *pci = imx6_pcie->pci;
> >       struct pcie_port *pp = &pci->pp;
> > @@ -581,7 +581,7 @@ static int __init imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
> >       return 0;
> >  }
> >
> > -static int __init imx6_pcie_probe(struct device_d *dev)
> > +static int imx6_pcie_probe(struct device_d *dev)
> >  {
> >       struct resource *iores;
> >       struct dw_pcie *pci;
> > @@ -606,6 +606,9 @@ static int __init imx6_pcie_probe(struct device_d *dev)
> >
> >       /* Fetch GPIOs */
> >       imx6_pcie->reset_gpio = of_get_named_gpio(np, "reset-gpio", 0);
> > +     if (imx6_pcie->reset_gpio == -EPROBE_DEFER)
> > +             return imx6_pcie->reset_gpio;
>
> Normally probe function run only once in barebox and in that case I do
> not care about loosing memory. When doing probe deferral here we loose a
> private data struct with each deferred probe here.
>
> Before returning -EPROBE_DEFER Here we already claimed a iomem resource using
> dev_request_mem_resource() which will fail during next probe, so I
> believe this patch doesn't work.
>

Yeah, it just happens to be that in Barebox 74164 GPIO driver gets
probed before PCIe, so this patch isn't strictly needed on i.MX7
(unlike on Linux). The simplest solution, I think, would be to move
GPIO request before dev_request_mem_resource(), which is my plan for
v2. If you'd rather this patch be dropped, since, technically things
are working without it, let me know.

Thanks,
Andrey Smirnov

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