linux-kernel - Re: [PATCH 2/2] spi: qup: Request CS GPIO's during probe

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Date:	Tue, 17 Mar 2015 13:02:08 +0200
From:	"Ivan T. Ivanov" <iivanov@...sol.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Mark Brown <broonie@...nel.org>, linus.walleij@...aro.org,
	linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] spi: qup: Request CS GPIO's during probe

Hi, 

On Mon, 2015-03-09 at 11:53 -0700, Stephen Boyd wrote:
> On 03/09/15 01:20, Ivan T. Ivanov wrote:
> > Hi Stephen,
> > 
> > > On Mar 6, 2015, at 8:34 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> > > On 03/06/15 07:26, Ivan T. Ivanov wrote:
> > > > Ensure that driver is owner of the GPIO's used for CS signals.
> > > Why? What happens if we don’t?
> > We can have wrong DT configuration, which could reconfigure
> > GPIO’s without any warning or error.
> 
> Ouch. That sounds bad. Can you please add this information to the commit
> text?
> 
> > > > Signed-off-by: Ivan T. Ivanov <iivanov@...sol.com>
> > > > ---
> > > > drivers/spi/spi-qup.c | 17 ++++++++++++++++-
> > > > 1 file changed, 16 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/spi/spi-qup.c b/drivers/spi/spi-qup.c
> > > > index 2b2c359..a07ba46 100644
> > > > --- a/drivers/spi/spi-qup.c
> > > > +++ b/drivers/spi/spi-qup.c
> > > > @@ -14,11 +14,13 @@
> > > > #include <linux/clk.h>
> > > > #include <linux/delay.h>
> > > > #include <linux/err.h>
> > > > +#include <linux/gpio.h>
> > > > #include <linux/interrupt.h>
> > > > #include <linux/io.h>
> > > > #include <linux/list.h>
> > > > #include <linux/module.h>
> > > > #include <linux/of.h>
> > > > +#include <linux/of_gpio.h>
> > > > #include <linux/platform_device.h>
> > > > #include <linux/pm_runtime.h>
> > > > #include <linux/spi/spi.h>
> > > > @@ -499,7 +501,7 @@ static int spi_qup_probe(struct platform_device *pdev)
> > > >         struct device *dev;
> > > >         void __iomem *base;
> > > >         u32 max_freq, iomode, num_cs;
> > > > -       int ret, irq, size;
> > > > +       int ret, irq, size, cs, cs_gpio;
> > > > 
> > > >         dev = &pdev->dev;
> > > >         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > > @@ -556,6 +558,19 @@ static int spi_qup_probe(struct platform_device *pdev)
> > > >         else
> > > >                 master->num_chipselect = num_cs;
> > > > 
> > > > +       for (cs = 0; cs < master->num_chipselect; cs++) {
> > > > +               cs_gpio = of_get_named_gpio(dev->of_node, "cs-gpios", cs);
> > > > +
> > > > +               if (!gpio_is_valid(cs_gpio))
> > > > +                       continue;
> > > > +
> > > > +               ret = devm_gpio_request(&pdev->dev, cs_gpio, "spi-qup-cs");
> > > > +               if (ret) {
> > > > +                       dev_err(&pdev->dev, "can't get cs gpios\n");
> > > > +                       goto error;
> > > > +               }
> > > > +       }
> > > > +
> > > >         master->bus_num = pdev->id;
> > > Is this related to [1]? In that case I was just relying on DT/pinctrl to
> > > properly request the gpios.
> > But the DT/pinctrl did not request GPIO’s, it just configure them.
> > For some reason we are ending without any pinctrl_map of type
> > PIN_MAP_TYPE_MUX_GROUP, which is used for pin reservation.

I will like to withdraw this patch. It fix the problem only
for CS lines, but misconfiguration could happen also for the
rest for the lines.

I will take a look in the pinctrl core code to see would it
be possible to print warning or something, when one driver
reconfigure pins already configured by another driver.

Regards,
Ivan  




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