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

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Date:	Mon, 09 Mar 2015 11:53:42 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	"Ivan T. Ivanov" <iivanov@...sol.com>
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

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. 
>

Ah ok. I seem to be misremembering the details.

Can you please use the gpiod interfaces here (devm_gpiod_get_index)?
That's more modern. Also, don't print any error because -EPROBE_DEFER
may come out and because __gpiod_get_index() already prints an error on
failure at the debug level.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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