* [PATCH 1/4] spi: davinci: Set prescale value based on register value
[not found] ` <1436903127-6777-1-git-send-email-fcooper-l0cyMroinI0@public.gmane.org>
@ 2015-07-14 19:45 ` Franklin S Cooper Jr
2015-07-14 19:45 ` [PATCH 2/4] spi: davinci: Choose correct pre-scaler limit based on SOC Franklin S Cooper Jr
1 sibling, 0 replies; 5+ messages in thread
From: Franklin S Cooper Jr @ 2015-07-14 19:45 UTC (permalink / raw)
To: linux-spi-u79uwXL29TY76Z2rM5mHXA
Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r,
linux-kernel-u79uwXL29TY76Z2rM5mHXA,
devicetree-u79uwXL29TY76Z2rM5mHXA, Franklin S Cooper Jr
Within davinci_spi_get_prescale() the prescale has two meanings. First one
being the calculated prescale value and then at the end translates it to the
prescale value that will be written to the SPI register.
At first glance this can be confusing especially when comparing the minimum
prescale value against what is seen in the TRM.
To simplify things make it clear that the calculated prescale value will always
be based on the value that will be written into the SPI register.
Signed-off-by: Franklin S Cooper Jr <fcooper-l0cyMroinI0@public.gmane.org>
---
drivers/spi/spi-davinci.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index 987afeb..b4605c4 100644
--- a/drivers/spi/spi-davinci.c
+++ b/drivers/spi/spi-davinci.c
@@ -255,7 +255,7 @@ static void davinci_spi_chipselect(struct spi_device *spi, int value)
* This function calculates the prescale value that generates a clock rate
* less than or equal to the specified maximum.
*
- * Returns: calculated prescale - 1 for easy programming into SPI registers
+ * Returns: calculated prescale value for easy programming into SPI registers
* or negative error number if valid prescalar cannot be updated.
*/
static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
@@ -263,12 +263,13 @@ static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
{
int ret;
- ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz);
+ /* Subtract 1 to match what will be programmed into SPI register. */
+ ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz) - 1;
- if (ret < 1 || ret > 256)
+ if (ret < 0 || ret > 255)
return -EINVAL;
- return ret - 1;
+ return ret;
}
/**
--
1.9.1
--
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^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/4] spi: davinci: Choose correct pre-scaler limit based on SOC
[not found] ` <1436903127-6777-1-git-send-email-fcooper-l0cyMroinI0@public.gmane.org>
2015-07-14 19:45 ` [PATCH 1/4] spi: davinci: Set prescale value based on register value Franklin S Cooper Jr
@ 2015-07-14 19:45 ` Franklin S Cooper Jr
1 sibling, 0 replies; 5+ messages in thread
From: Franklin S Cooper Jr @ 2015-07-14 19:45 UTC (permalink / raw)
To: linux-spi-u79uwXL29TY76Z2rM5mHXA
Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r,
linux-kernel-u79uwXL29TY76Z2rM5mHXA,
devicetree-u79uwXL29TY76Z2rM5mHXA, Franklin S Cooper Jr
Currently the pre-scaler limit is incorrect. The value differs slightly
for various devices so a single value can't be used. Using the compatible
field select the correct pre-scaler limit.
Add new compatible field value for Keystone devices to support their
unique pre-scaler limit value.
Signed-off-by: Franklin S Cooper Jr <fcooper-l0cyMroinI0@public.gmane.org>
---
.../devicetree/bindings/spi/spi-davinci.txt | 2 +
drivers/spi/spi-davinci.c | 43 ++++++++++++++++++----
include/linux/platform_data/spi-davinci.h | 1 +
3 files changed, 39 insertions(+), 7 deletions(-)
diff --git a/Documentation/devicetree/bindings/spi/spi-davinci.txt b/Documentation/devicetree/bindings/spi/spi-davinci.txt
index 12ecfe9..d1e914a 100644
--- a/Documentation/devicetree/bindings/spi/spi-davinci.txt
+++ b/Documentation/devicetree/bindings/spi/spi-davinci.txt
@@ -12,6 +12,8 @@ Required properties:
- compatible:
- "ti,dm6441-spi" for SPI used similar to that on DM644x SoC family
- "ti,da830-spi" for SPI used similar to that on DA8xx SoC family
+ - "ti,keystone-spi" for SPI used similar to that on Keystone2 SoC
+ family
- reg: Offset and length of SPI controller register space
- num-cs: Number of chip selects. This includes internal as well as
GPIO chip selects.
diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index b4605c4..3cf9faa 100644
--- a/drivers/spi/spi-davinci.c
+++ b/drivers/spi/spi-davinci.c
@@ -139,6 +139,8 @@ struct davinci_spi {
u32 (*get_tx)(struct davinci_spi *);
u8 *bytes_per_word;
+
+ u8 prescaler_limit;
};
static struct davinci_spi_config davinci_spi_default_cfg;
@@ -266,7 +268,7 @@ static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
/* Subtract 1 to match what will be programmed into SPI register. */
ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz) - 1;
- if (ret < 0 || ret > 255)
+ if (ret < dspi->prescaler_limit || ret > 255)
return -EINVAL;
return ret;
@@ -833,13 +835,40 @@ rx_dma_failed:
}
#if defined(CONFIG_OF)
+
+/* OF SPI data structure */
+struct davinci_spi_of_data {
+ u8 version;
+ u8 prescaler_limit;
+};
+
+static const struct davinci_spi_of_data dm6441_spi_data = {
+ .version = SPI_VERSION_1,
+ .prescaler_limit = 2,
+};
+
+static const struct davinci_spi_of_data da830_spi_data = {
+ .version = SPI_VERSION_2,
+ .prescaler_limit = 2,
+};
+
+static const struct davinci_spi_of_data keystone_spi_data = {
+ .version = SPI_VERSION_1,
+ .prescaler_limit = 0,
+};
+
static const struct of_device_id davinci_spi_of_match[] = {
{
.compatible = "ti,dm6441-spi",
+ .data = &dm6441_spi_data,
},
{
.compatible = "ti,da830-spi",
- .data = (void *)SPI_VERSION_2,
+ .data = &da830_spi_data,
+ },
+ {
+ .compatible = "ti,keystone-spi",
+ .data = &keystone_spi_data,
},
{ },
};
@@ -858,21 +887,21 @@ static int spi_davinci_get_pdata(struct platform_device *pdev,
struct davinci_spi *dspi)
{
struct device_node *node = pdev->dev.of_node;
+ struct davinci_spi_of_data *spi_data;
struct davinci_spi_platform_data *pdata;
unsigned int num_cs, intr_line = 0;
const struct of_device_id *match;
pdata = &dspi->pdata;
- pdata->version = SPI_VERSION_1;
match = of_match_device(davinci_spi_of_match, &pdev->dev);
if (!match)
return -ENODEV;
- /* match data has the SPI version number for SPI_VERSION_2 */
- if (match->data == (void *)SPI_VERSION_2)
- pdata->version = SPI_VERSION_2;
+ spi_data = (struct davinci_spi_of_data *)match->data;
+ pdata->version = spi_data->version;
+ pdata->prescaler_limit = spi_data->prescaler_limit;
/*
* default num_cs is 1 and all chipsel are internal to the chip
* indicated by chip_sel being NULL or cs_gpios being NULL or
@@ -992,7 +1021,7 @@ static int davinci_spi_probe(struct platform_device *pdev)
dspi->bitbang.chipselect = davinci_spi_chipselect;
dspi->bitbang.setup_transfer = davinci_spi_setup_transfer;
-
+ dspi->prescaler_limit = pdata->prescaler_limit;
dspi->version = pdata->version;
dspi->bitbang.flags = SPI_NO_CS | SPI_LSB_FIRST | SPI_LOOP;
diff --git a/include/linux/platform_data/spi-davinci.h b/include/linux/platform_data/spi-davinci.h
index 8dc2fa47..f4edcb0 100644
--- a/include/linux/platform_data/spi-davinci.h
+++ b/include/linux/platform_data/spi-davinci.h
@@ -49,6 +49,7 @@ struct davinci_spi_platform_data {
u8 num_chipselect;
u8 intr_line;
u8 *chip_sel;
+ u8 prescaler_limit;
bool cshold_bug;
enum dma_event_q dma_event_q;
};
--
1.9.1
--
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^ permalink raw reply related [flat|nested] 5+ messages in thread