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Message-Id: <20240315015708.13948-1-justin.swartz@risingedge.co.za>
Date: Fri, 15 Mar 2024 03:57:07 +0200
From: Justin Swartz <justin.swartz@...ingedge.co.za>
To: Mark Brown <broonie@...nel.org>,
Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Justin Swartz <justin.swartz@...ingedge.co.za>,
linux-spi@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org
Subject: [PATCH] spi: mt7621: allow GPIO chip select lines
Extract a magic number, from mt7621_spi_probe(), used to
declare the number of chip select lines (which co-incides
with the native chip select count of 2) to a macro.
Use the newly defined MT7621_NATIVE_CS_COUNT macro to
instead populate both the spi_controller's max_native_cs
and num_chipselect members.
Declare that the spi_controller should use_gpio_descriptors
if present in the device properties (such as those declared
in the cs-gpio property of a "ralink,mt7621-spi" compatible
device-tree node) so that the SPI core will recalulcate
num_chipselect to account for the GPIO descriptors that
it should have populated in the cs_gpiod array member.
Add the mt7621_spi_set_cs_gpio() function to control the
logical state of a GPIO chip select line, agnostic of the
electrical line state and activation polarity.
Add the mt7621_spi_cleanup() function to ensure that every
GPIO chip select will be deactivated when no longer in use.
Extend mt7621_spi_setup() so that if an SPI device is
associated with a GPIO chip select, its chip select line
will be deactivated before use.
Rename mt7621_spi_set_cs() to mt7621_spi_set_native_cs(),
and redefine mt7621_spi_set_cs() to determine whether:
to call mt7621_spi_set_cs_gpio(), in the case of the
passed SPI device being associated with a GPIO chip
select line,
or to call mt7621_spi_set_set_native_cs() instead.
Modify mt7621_transfer_one_message() to take into account
that mt7621_spi_set_cs() now returns an int and should use
the returned value for spi_message status indication if a
failure related to GPIO access has occured.
Signed-off-by: Justin Swartz <justin.swartz@...ingedge.co.za>
---
See Documentation/devicetree/bindings/spi/spi-controller.yaml
for information about cs-gpios semantics.
Example:
&spi0 {
cs-gpios = <0>, <0>,
<&gpio 18 GPIO_ACTIVE_LOW>, /* WDT_RST_N */
<&gpio 19 GPIO_ACTIVE_HIGH>; /* PERST_N */
status = "ok";
...
spidev@2 {
compatible = "defective,by-design";
reg = <2>;
spi-max-frequency = <16000000>;
};
spidev@3 {
compatible = "defective,by-design";
reg = <3>;
spi-cs-high;
spi-max-frequency = <16000000>;
};
};
drivers/spi/spi-mt7621.c | 46 ++++++++++++++++++++++++++++++++++++----
1 file changed, 42 insertions(+), 4 deletions(-)
diff --git a/drivers/spi/spi-mt7621.c b/drivers/spi/spi-mt7621.c
index 4e9053d03..87e164c86 100644
--- a/drivers/spi/spi-mt7621.c
+++ b/drivers/spi/spi-mt7621.c
@@ -52,6 +52,8 @@
#define MT7621_CPOL BIT(4)
#define MT7621_LSB_FIRST BIT(3)
+#define MT7621_NATIVE_CS_COUNT 2
+
struct mt7621_spi {
struct spi_controller *host;
void __iomem *base;
@@ -75,7 +77,19 @@ static inline void mt7621_spi_write(struct mt7621_spi *rs, u32 reg, u32 val)
iowrite32(val, rs->base + reg);
}
-static void mt7621_spi_set_cs(struct spi_device *spi, int enable)
+static int mt7621_spi_set_cs_gpio(struct spi_device *spi, int enable)
+{
+ struct gpio_desc *gpiod = spi_get_csgpiod(spi, 0);
+ int cs = spi_get_chipselect(spi, 0);
+ int status = gpiod_direction_output(gpiod, enable);
+
+ if (status)
+ dev_err(&spi->dev, "set_gpio: failed to set CS%d", cs);
+
+ return status;
+}
+
+static void mt7621_spi_set_native_cs(struct spi_device *spi, int enable)
{
struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
int cs = spi_get_chipselect(spi, 0);
@@ -99,6 +113,15 @@ static void mt7621_spi_set_cs(struct spi_device *spi, int enable)
mt7621_spi_write(rs, MT7621_SPI_POLAR, polar);
}
+static int mt7621_spi_set_cs(struct spi_device *spi, int enable)
+{
+ if (spi_is_csgpiod(spi))
+ return mt7621_spi_set_cs_gpio(spi, enable);
+
+ mt7621_spi_set_native_cs(spi,enable);
+ return 0;
+}
+
static int mt7621_spi_prepare(struct spi_device *spi, unsigned int speed)
{
struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
@@ -266,7 +289,9 @@ static int mt7621_spi_transfer_one_message(struct spi_controller *host,
}
/* Assert CS */
- mt7621_spi_set_cs(spi, 1);
+ status = mt7621_spi_set_cs(spi, 1);
+ if (status)
+ goto msg_done;
m->actual_length = 0;
list_for_each_entry(t, &m->transfers, transfer_list) {
@@ -290,7 +315,7 @@ static int mt7621_spi_transfer_one_message(struct spi_controller *host,
/* Flush data and deassert CS */
mt7621_spi_flush(rs);
- mt7621_spi_set_cs(spi, 0);
+ status = mt7621_spi_set_cs(spi, 0);
msg_done:
m->status = status;
@@ -313,9 +338,18 @@ static int mt7621_spi_setup(struct spi_device *spi)
return -EINVAL;
}
+ if (spi_is_csgpiod(spi))
+ return mt7621_spi_set_cs_gpio(spi, 0);
+
return 0;
}
+static void mt7621_spi_cleanup(struct spi_device *spi)
+{
+ if (spi_is_csgpiod(spi))
+ mt7621_spi_set_cs_gpio(spi, 0);
+}
+
static const struct of_device_id mt7621_spi_match[] = {
{ .compatible = "ralink,mt7621-spi" },
{},
@@ -353,10 +387,14 @@ static int mt7621_spi_probe(struct platform_device *pdev)
host->mode_bits = SPI_LSB_FIRST;
host->flags = SPI_CONTROLLER_HALF_DUPLEX;
host->setup = mt7621_spi_setup;
+ host->cleanup = mt7621_spi_cleanup;
host->transfer_one_message = mt7621_spi_transfer_one_message;
host->bits_per_word_mask = SPI_BPW_MASK(8);
host->dev.of_node = pdev->dev.of_node;
- host->num_chipselect = 2;
+
+ host->max_native_cs = MT7621_NATIVE_CS_COUNT;
+ host->num_chipselect = host->max_native_cs;
+ host->use_gpio_descriptors = true;
dev_set_drvdata(&pdev->dev, host);
--
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