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Date: Wed, 24 May 2017 05:42:38 +0000
From: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To: Andy Shevchenko <andy.shevchenko@...il.com>
CC: Mark Brown <broonie@...nel.org>,
linux-spi <linux-spi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] spi: use gpio_desc instead of numeric gpio
On 24/05/17 08:43, Chris Packham wrote:
> Hi Andy,
>
> On 24/05/17 06:28, Andy Shevchenko wrote:
>> On Tue, May 23, 2017 at 7:03 AM, Chris Packham
>> <chris.packham@...iedtelesis.co.nz> wrote:
>>> By using a gpio_desc and gpiod_set_value() instead of a numeric gpio and
>>> gpio_set_value() the gpio flags are taken into account. This is useful
>>> when using a gpio chip-select to supplement a controllers native
>>> chip-select.
>>
>> I think would be better to move everything in SPI core to GPIO descriptors.
>
> I did consider it but it's a big change and I don't have access a lot of
> gear to test on (maybe 2 or 3 SoCs with a SPI host controller and the
> same SPI-NOR chips).
>
> I can give it a try. Perhaps converting the spi core structures over and
> leaving the slaves using numeric gpios. Then later converting the slaves.
>
OK so I've had a look at this. The changes to change struct spi_master
to use gpio_desc in drivers/spi/spi-gpio.c are pretty straight forward
(in-line patch below, apologies for MUA wrapping).
There are a few SPI host drivers that deal with cs_gpios directly.
spi-mt65xx.c and spi-davinci.c would be trivial to update. spi-ep93xx.c
and spi-imx.c are harder because they handle non-dt platforms.
Changing struct spi_device to use gpio_desc would be wider reaching but
probably automatable s/gpio_set_value/gpiod_set_value/.
I'm a little too nervous about messing up spi-ep93xx.c and spi-ep93xx.c
to push ahead with changing all of SPI core. I'd be happy to help out
someone with access to platforms using those.
-- 8< --
index b39c0f9956dd..80a96d3daa45 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -40,6 +40,7 @@
#include <linux/ioport.h>
#include <linux/acpi.h>
#include <linux/highmem.h>
+#include <linux/gpio/consumer.h>
#define CREATE_TRACE_POINTS
#include <trace/events/spi.h>
@@ -531,8 +532,8 @@ int spi_add_device(struct spi_device *spi)
goto done;
}
- if (master->cs_gpios)
- spi->cs_gpio = master->cs_gpios[spi->chip_select];
+ if (master->cs_gpios[spi->chip_select])
+ spi->cs_gpio =
desc_to_gpio(master->cs_gpios[spi->chip_select]);
/* Drivers may modify this initial i/o setup, but will
* normally rely on the device being setup. Devices
@@ -1878,7 +1879,8 @@ EXPORT_SYMBOL_GPL(spi_alloc_master);
#ifdef CONFIG_OF
static int of_spi_register_master(struct spi_master *master)
{
- int nb, i, *cs;
+ int nb, i;
+ struct gpio_desc **cs;
struct device_node *np = master->dev.of_node;
if (!np)
@@ -1894,7 +1896,7 @@ static int of_spi_register_master(struct
spi_master *master)
return nb;
cs = devm_kzalloc(&master->dev,
- sizeof(int) * master->num_chipselect,
+ sizeof(*master->cs_gpios) *
master->num_chipselect,
GFP_KERNEL);
master->cs_gpios = cs;
@@ -1902,10 +1904,16 @@ static int of_spi_register_master(struct
spi_master *master)
return -ENOMEM;
for (i = 0; i < master->num_chipselect; i++)
- cs[i] = -ENOENT;
+ cs[i] = NULL;
- for (i = 0; i < nb; i++)
- cs[i] = of_get_named_gpio(np, "cs-gpios", i);
+ for (i = 0; i < nb; i++) {
+ struct gpio_desc *gpio;
+
+ gpio = devm_gpiod_get_index(&master->dev, "cs", i,
+ GPIOD_OUT_HIGH);
+ if (!IS_ERR(gpio))
+ cs[i] = gpio;
+ }
return 0;
}
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 935bd2854ff1..46960ca62d5b 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -556,7 +556,7 @@ struct spi_master {
struct spi_message *message);
/* gpio chip select */
- int *cs_gpios;
+ struct gpio_desc **cs_gpios;
/* statistics */
struct spi_statistics statistics;
-- >8 --
>>
>>>
>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> ---
>>>
>>> Notes:
>>> My specific use-case is I have a board that uses the spi-orion driver but
>>> only has one CS pin available. In order to access two spi slave devices the
>>> board has a 1-of-2 decoder/demultiplexer which is driven via a gpio.
>>>
>>> The problem is that for one of the 2 slave devices the gpio level required
>>> is opposite to the chip-select so I can't simply specify "spi-cs-high".
>>> With this change I can flag the gpio as active low and the gpio subsystem
>>> takes care of the additional inversion required.
>>>
>>> drivers/spi/spi.c | 5 ++++-
>>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
>>> index 6f87fec409b5..b39c0f9956dd 100644
>>> --- a/drivers/spi/spi.c
>>> +++ b/drivers/spi/spi.c
>>> @@ -725,7 +725,10 @@ static void spi_set_cs(struct spi_device *spi, bool enable)
>>> enable = !enable;
>>>
>>> if (gpio_is_valid(spi->cs_gpio)) {
>>> - gpio_set_value(spi->cs_gpio, !enable);
>>> + struct gpio_desc *gpio = gpio_to_desc(spi->cs_gpio);
>>> +
>>> + if (gpio)
>>> + gpiod_set_value(gpio, !enable);
>>> /* Some SPI masters need both GPIO CS & slave_select */
>>> if ((spi->master->flags & SPI_MASTER_GPIO_SS) &&
>>> spi->master->set_cs)
>>> --
>>> 2.13.0
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-spi" in
>>> the body of a message to majordomo@...r.kernel.org
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>>
>>
>
>
>
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