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Subject[PATCH] spi: spi-fsl-spi: support use of the SPISEL_BOOT signal on MPC8309
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The MPC8309 has a dedicated signal, SPISEL_BOOT, usually used as chip
select for the flash device from which the bootloader is loaded. It is
not an ordinary gpio, but is simply controlled via the SPI_CS register
in the system configuration.

To allow accessing such a spi slave, we need to teach
fsl_spi_cs_control() how to control the SPISEL_BOOT signal. To
distinguish the gpio-controlled slaves, continue to have those use
chip_select values of 0..ngpios-1, and use chip_select == ngpios for
the boot flash.

I'm not too happy with all the ifdeffery, but it seems to be necessary
for guarding the sysdev/fsl_soc.h and use of
get_immrbase() (spi-fsl-lib.c already contains similar ifdeffery).

Googling suggests that the MPC8306 is similar, with the SPI_CS
register at the same offset.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
---
.../devicetree/bindings/spi/fsl-spi.txt | 4 ++
drivers/spi/spi-fsl-lib.h | 2 +
drivers/spi/spi-fsl-spi.c | 40 ++++++++++++++++---
3 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/spi/fsl-spi.txt b/Documentation/devicetree/bindings/spi/fsl-spi.txt
index 8854004a1d3a..411375eac54d 100644
--- a/Documentation/devicetree/bindings/spi/fsl-spi.txt
+++ b/Documentation/devicetree/bindings/spi/fsl-spi.txt
@@ -18,6 +18,10 @@ Optional properties:
- gpios : specifies the gpio pins to be used for chipselects.
The gpios will be referred to as reg = <index> in the SPI child nodes.
If unspecified, a single SPI device without a chip select can be used.
+- fsl,spisel_boot : for the MPC8306 and MPC8309, specifies that the
+ SPISEL_BOOT signal is used as chip select for a slave device. Use
+ reg = <number of gpios> in the corresponding child node, i.e. 0 if
+ the gpios property is not present.

Example:
spi@4c0 {
diff --git a/drivers/spi/spi-fsl-lib.h b/drivers/spi/spi-fsl-lib.h
index f303f306b38e..483734bc1b1e 100644
--- a/drivers/spi/spi-fsl-lib.h
+++ b/drivers/spi/spi-fsl-lib.h
@@ -95,8 +95,10 @@ static inline u32 mpc8xxx_spi_read_reg(__be32 __iomem *reg)

struct mpc8xxx_spi_probe_info {
struct fsl_spi_platform_data pdata;
+ int ngpios;
int *gpios;
bool *alow_flags;
+ __be32 __iomem *immr_spi_cs;
};

extern u32 mpc8xxx_spi_tx_buf_u8(struct mpc8xxx_spi *mpc8xxx_spi);
diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 8f2e97857e8b..3d7b50c65f36 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -39,6 +39,14 @@
#include <linux/spi/spi_bitbang.h>
#include <linux/types.h>

+#ifdef CONFIG_FSL_SOC
+#include <sysdev/fsl_soc.h>
+#endif
+
+/* Specific to the MPC8306/MPC8309 */
+#define IMMR_SPI_CS_OFFSET 0x14c
+#define SPI_BOOT_SEL_BIT 0x80000000
+
#include "spi-fsl-lib.h"
#include "spi-fsl-cpm.h"
#include "spi-fsl-spi.h"
@@ -701,10 +709,17 @@ static void fsl_spi_cs_control(struct spi_device *spi, bool on)
struct fsl_spi_platform_data *pdata = dev_get_platdata(dev);
struct mpc8xxx_spi_probe_info *pinfo = to_of_pinfo(pdata);
u16 cs = spi->chip_select;
- int gpio = pinfo->gpios[cs];
- bool alow = pinfo->alow_flags[cs];

- gpio_set_value(gpio, on ^ alow);
+ if (cs < pinfo->ngpios) {
+ int gpio = pinfo->gpios[cs];
+ bool alow = pinfo->alow_flags[cs];
+
+ gpio_set_value(gpio, on ^ alow);
+ } else {
+ if (WARN_ON_ONCE(cs > pinfo->ngpios || !pinfo->immr_spi_cs))
+ return;
+ iowrite32be(on ? SPI_BOOT_SEL_BIT : 0, pinfo->immr_spi_cs);
+ }
}

static int of_fsl_spi_get_chipselects(struct device *dev)
@@ -712,12 +727,15 @@ static int of_fsl_spi_get_chipselects(struct device *dev)
struct device_node *np = dev->of_node;
struct fsl_spi_platform_data *pdata = dev_get_platdata(dev);
struct mpc8xxx_spi_probe_info *pinfo = to_of_pinfo(pdata);
+ bool spisel_boot = IS_ENABLED(CONFIG_FSL_SOC) &&
+ of_property_read_bool(np, "fsl,spisel_boot");
int ngpios;
int i = 0;
int ret;

ngpios = of_gpio_count(np);
- if (ngpios <= 0) {
+ ngpios = max(ngpios, 0);
+ if (ngpios == 0 && !spisel_boot) {
/*
* SPI w/o chip-select line. One SPI device is still permitted
* though.
@@ -726,6 +744,7 @@ static int of_fsl_spi_get_chipselects(struct device *dev)
return 0;
}

+ pinfo->ngpios = ngpios;
pinfo->gpios = kmalloc_array(ngpios, sizeof(*pinfo->gpios),
GFP_KERNEL);
if (!pinfo->gpios)
@@ -769,7 +788,18 @@ static int of_fsl_spi_get_chipselects(struct device *dev)
}
}

- pdata->max_chipselect = ngpios;
+#if IS_ENABLED(CONFIG_FSL_SOC)
+ if (spisel_boot) {
+ pinfo->immr_spi_cs = ioremap(get_immrbase() + IMMR_SPI_CS_OFFSET, 4);
+ if (!pinfo->immr_spi_cs) {
+ ret = -ENOMEM;
+ i = ngpios - 1;
+ goto err_loop;
+ }
+ }
+#endif
+
+ pdata->max_chipselect = ngpios + spisel_boot;
pdata->cs_control = fsl_spi_cs_control;

return 0;
--
2.20.1
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