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linux/drivers/spi/spi_mpc83xx.c
Anton Vorontsov a44648b057 spi_mpc83xx: fix prescale modulus calculation 
Long ago I've noticed (but didn't pay much attention) that
spi_mpc83xx using PM calculations that differs from what
specs describe. I.e.

u8 pm = mpc83xx_spi->spibrg / (spi->max_speed_hz * 4);

While specs says: "The SPI baud rate generator clock source (either
system clock or system clock divided by 16, depending on DIV16 bit) is
divided by 4 * ([PM] + 1), a range from 4 to 64.".

Thus " - 1" is missing in the spi_mpc83xx's formula.

Why nobody noticed that bug? Probably because sysclk usually less then
user expects, e.g. you expect 200 MHz, but real clock is 198 MHz,
and integer rounding helps when this formula is used.

Suppose it's SPI in QE, SYSCLK at 198 MHz, thus SPIBRG at 99MHz, 25 MHz
requested.

PM = (99MHz / ( 25 MHz * 4 )), PM == 0, output SPICLK will be 24.75 MHz

At lower frequencies this bug is more noticeable, though.

And this bug shows itself in all its beauty if SYSCLK is equal or a bit
more than you expect (200 MHz SYSCLK, 100 MHz SPIBRG):
PM = (100MHz / ( 25 MHz * 4 )), PM == 1, output SPICLK will be 12.625 MHz!

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-08-11 15:47:41 -07:00

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/*
* MPC83xx SPI controller driver.
*
* Maintainer: Kumar Gala
*
* Copyright (C) 2006 Polycom, Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/device.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/platform_device.h>
#include <linux/fsl_devices.h>
#include <asm/irq.h>
#include <asm/io.h>
/* SPI Controller registers */
struct mpc83xx_spi_reg {
u8 res1[0x20];
__be32 mode;
__be32 event;
__be32 mask;
__be32 command;
__be32 transmit;
__be32 receive;
};
/* SPI Controller mode register definitions */
#define SPMODE_LOOP (1 << 30)
#define SPMODE_CI_INACTIVEHIGH (1 << 29)
#define SPMODE_CP_BEGIN_EDGECLK (1 << 28)
#define SPMODE_DIV16 (1 << 27)
#define SPMODE_REV (1 << 26)
#define SPMODE_MS (1 << 25)
#define SPMODE_ENABLE (1 << 24)
#define SPMODE_LEN(x) ((x) << 20)
#define SPMODE_PM(x) ((x) << 16)
#define SPMODE_OP (1 << 14)
/*
* Default for SPI Mode:
* SPI MODE 0 (inactive low, phase middle, MSB, 8-bit length, slow clk
*/
#define SPMODE_INIT_VAL (SPMODE_CI_INACTIVEHIGH | SPMODE_DIV16 | SPMODE_REV | \
SPMODE_MS | SPMODE_LEN(7) | SPMODE_PM(0xf))
/* SPIE register values */
#define SPIE_NE 0x00000200 /* Not empty */
#define SPIE_NF 0x00000100 /* Not full */
/* SPIM register values */
#define SPIM_NE 0x00000200 /* Not empty */
#define SPIM_NF 0x00000100 /* Not full */
/* SPI Controller driver's private data. */
struct mpc83xx_spi {
/* bitbang has to be first */
struct spi_bitbang bitbang;
struct completion done;
struct mpc83xx_spi_reg __iomem *base;
/* rx & tx bufs from the spi_transfer */
const void *tx;
void *rx;
/* functions to deal with different sized buffers */
void (*get_rx) (u32 rx_data, struct mpc83xx_spi *);
u32(*get_tx) (struct mpc83xx_spi *);
unsigned int count;
u32 irq;
unsigned nsecs; /* (clock cycle time)/2 */
u32 spibrg; /* SPIBRG input clock */
u32 rx_shift; /* RX data reg shift when in qe mode */
u32 tx_shift; /* TX data reg shift when in qe mode */
bool qe_mode;
void (*activate_cs) (u8 cs, u8 polarity);
void (*deactivate_cs) (u8 cs, u8 polarity);
};
static inline void mpc83xx_spi_write_reg(__be32 __iomem * reg, u32 val)
{
out_be32(reg, val);
}
static inline u32 mpc83xx_spi_read_reg(__be32 __iomem * reg)
{
return in_be32(reg);
}
#define MPC83XX_SPI_RX_BUF(type) \
void mpc83xx_spi_rx_buf_##type(u32 data, struct mpc83xx_spi *mpc83xx_spi) \
{ \
type * rx = mpc83xx_spi->rx; \
*rx++ = (type)(data >> mpc83xx_spi->rx_shift); \
mpc83xx_spi->rx = rx; \
}
#define MPC83XX_SPI_TX_BUF(type) \
u32 mpc83xx_spi_tx_buf_##type(struct mpc83xx_spi *mpc83xx_spi) \
{ \
u32 data; \
const type * tx = mpc83xx_spi->tx; \
if (!tx) \
return 0; \
data = *tx++ << mpc83xx_spi->tx_shift; \
mpc83xx_spi->tx = tx; \
return data; \
}
MPC83XX_SPI_RX_BUF(u8)
MPC83XX_SPI_RX_BUF(u16)
MPC83XX_SPI_RX_BUF(u32)
MPC83XX_SPI_TX_BUF(u8)
MPC83XX_SPI_TX_BUF(u16)
MPC83XX_SPI_TX_BUF(u32)
static void mpc83xx_spi_chipselect(struct spi_device *spi, int value)
{
struct mpc83xx_spi *mpc83xx_spi;
u8 pol = spi->mode & SPI_CS_HIGH ? 1 : 0;
mpc83xx_spi = spi_master_get_devdata(spi->master);
if (value == BITBANG_CS_INACTIVE) {
if (mpc83xx_spi->deactivate_cs)
mpc83xx_spi->deactivate_cs(spi->chip_select, pol);
}
if (value == BITBANG_CS_ACTIVE) {
u32 regval = mpc83xx_spi_read_reg(&mpc83xx_spi->base->mode);
u32 len = spi->bits_per_word;
u8 pm;
if (len == 32)
len = 0;
else
len = len - 1;
/* mask out bits we are going to set */
regval &= ~(SPMODE_CP_BEGIN_EDGECLK | SPMODE_CI_INACTIVEHIGH
| SPMODE_LEN(0xF) | SPMODE_DIV16
| SPMODE_PM(0xF) | SPMODE_REV | SPMODE_LOOP);
if (spi->mode & SPI_CPHA)
regval |= SPMODE_CP_BEGIN_EDGECLK;
if (spi->mode & SPI_CPOL)
regval |= SPMODE_CI_INACTIVEHIGH;
if (!(spi->mode & SPI_LSB_FIRST))
regval |= SPMODE_REV;
if (spi->mode & SPI_LOOP)
regval |= SPMODE_LOOP;
regval |= SPMODE_LEN(len);
if ((mpc83xx_spi->spibrg / spi->max_speed_hz) >= 64) {
pm = mpc83xx_spi->spibrg / (spi->max_speed_hz * 64) - 1;
if (pm > 0x0f) {
dev_err(&spi->dev, "Requested speed is too "
"low: %d Hz. Will use %d Hz instead.\n",
spi->max_speed_hz,
mpc83xx_spi->spibrg / 1024);
pm = 0x0f;
}
regval |= SPMODE_PM(pm) | SPMODE_DIV16;
} else {
pm = mpc83xx_spi->spibrg / (spi->max_speed_hz * 4);
if (pm)
pm--;
regval |= SPMODE_PM(pm);
}
/* Turn off SPI unit prior changing mode */
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, 0);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, regval);
if (mpc83xx_spi->activate_cs)
mpc83xx_spi->activate_cs(spi->chip_select, pol);
}
}
static
int mpc83xx_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
{
struct mpc83xx_spi *mpc83xx_spi;
u32 regval;
u8 bits_per_word;
u32 hz;
mpc83xx_spi = spi_master_get_devdata(spi->master);
if (t) {
bits_per_word = t->bits_per_word;
hz = t->speed_hz;
} else {
bits_per_word = 0;
hz = 0;
}
/* spi_transfer level calls that work per-word */
if (!bits_per_word)
bits_per_word = spi->bits_per_word;
/* Make sure its a bit width we support [4..16, 32] */
if ((bits_per_word < 4)
|| ((bits_per_word > 16) && (bits_per_word != 32)))
return -EINVAL;
mpc83xx_spi->rx_shift = 0;
mpc83xx_spi->tx_shift = 0;
if (bits_per_word <= 8) {
mpc83xx_spi->get_rx = mpc83xx_spi_rx_buf_u8;
mpc83xx_spi->get_tx = mpc83xx_spi_tx_buf_u8;
if (mpc83xx_spi->qe_mode) {
mpc83xx_spi->rx_shift = 16;
mpc83xx_spi->tx_shift = 24;
}
} else if (bits_per_word <= 16) {
mpc83xx_spi->get_rx = mpc83xx_spi_rx_buf_u16;
mpc83xx_spi->get_tx = mpc83xx_spi_tx_buf_u16;
if (mpc83xx_spi->qe_mode) {
mpc83xx_spi->rx_shift = 16;
mpc83xx_spi->tx_shift = 16;
}
} else if (bits_per_word <= 32) {
mpc83xx_spi->get_rx = mpc83xx_spi_rx_buf_u32;
mpc83xx_spi->get_tx = mpc83xx_spi_tx_buf_u32;
} else
return -EINVAL;
if (mpc83xx_spi->qe_mode && spi->mode & SPI_LSB_FIRST) {
mpc83xx_spi->tx_shift = 0;
if (bits_per_word <= 8)
mpc83xx_spi->rx_shift = 8;
else
mpc83xx_spi->rx_shift = 0;
}
/* nsecs = (clock period)/2 */
if (!hz)
hz = spi->max_speed_hz;
mpc83xx_spi->nsecs = (1000000000 / 2) / hz;
if (mpc83xx_spi->nsecs > MAX_UDELAY_MS * 1000)
return -EINVAL;
if (bits_per_word == 32)
bits_per_word = 0;
else
bits_per_word = bits_per_word - 1;
regval = mpc83xx_spi_read_reg(&mpc83xx_spi->base->mode);
/* mask out bits we are going to set */
regval &= ~(SPMODE_LEN(0xF) | SPMODE_REV);
regval |= SPMODE_LEN(bits_per_word);
if (!(spi->mode & SPI_LSB_FIRST))
regval |= SPMODE_REV;
/* Turn off SPI unit prior changing mode */
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, 0);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, regval);
return 0;
}
/* the spi->mode bits understood by this driver: */
#define MODEBITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
| SPI_LSB_FIRST | SPI_LOOP)
static int mpc83xx_spi_setup(struct spi_device *spi)
{
struct spi_bitbang *bitbang;
struct mpc83xx_spi *mpc83xx_spi;
int retval;
if (spi->mode & ~MODEBITS) {
dev_dbg(&spi->dev, "setup: unsupported mode bits %x\n",
spi->mode & ~MODEBITS);
return -EINVAL;
}
if (!spi->max_speed_hz)
return -EINVAL;
bitbang = spi_master_get_devdata(spi->master);
mpc83xx_spi = spi_master_get_devdata(spi->master);
if (!spi->bits_per_word)
spi->bits_per_word = 8;
retval = mpc83xx_spi_setup_transfer(spi, NULL);
if (retval < 0)
return retval;
dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec\n",
__FUNCTION__, spi->mode & (SPI_CPOL | SPI_CPHA),
spi->bits_per_word, 2 * mpc83xx_spi->nsecs);
/* NOTE we _need_ to call chipselect() early, ideally with adapter
* setup, unless the hardware defaults cooperate to avoid confusion
* between normal (active low) and inverted chipselects.
*/
/* deselect chip (low or high) */
spin_lock(&bitbang->lock);
if (!bitbang->busy) {
bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
ndelay(mpc83xx_spi->nsecs);
}
spin_unlock(&bitbang->lock);
return 0;
}
static int mpc83xx_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
{
struct mpc83xx_spi *mpc83xx_spi;
u32 word;
mpc83xx_spi = spi_master_get_devdata(spi->master);
mpc83xx_spi->tx = t->tx_buf;
mpc83xx_spi->rx = t->rx_buf;
mpc83xx_spi->count = t->len;
INIT_COMPLETION(mpc83xx_spi->done);
/* enable rx ints */
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mask, SPIM_NE);
/* transmit word */
word = mpc83xx_spi->get_tx(mpc83xx_spi);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->transmit, word);
wait_for_completion(&mpc83xx_spi->done);
/* disable rx ints */
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mask, 0);
return t->len - mpc83xx_spi->count;
}
irqreturn_t mpc83xx_spi_irq(s32 irq, void *context_data)
{
struct mpc83xx_spi *mpc83xx_spi = context_data;
u32 event;
irqreturn_t ret = IRQ_NONE;
/* Get interrupt events(tx/rx) */
event = mpc83xx_spi_read_reg(&mpc83xx_spi->base->event);
/* We need handle RX first */
if (event & SPIE_NE) {
u32 rx_data = mpc83xx_spi_read_reg(&mpc83xx_spi->base->receive);
if (mpc83xx_spi->rx)
mpc83xx_spi->get_rx(rx_data, mpc83xx_spi);
ret = IRQ_HANDLED;
}
if ((event & SPIE_NF) == 0)
/* spin until TX is done */
while (((event =
mpc83xx_spi_read_reg(&mpc83xx_spi->base->event)) &
SPIE_NF) == 0)
cpu_relax();
mpc83xx_spi->count -= 1;
if (mpc83xx_spi->count) {
if (mpc83xx_spi->tx) {
u32 word = mpc83xx_spi->get_tx(mpc83xx_spi);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->transmit,
word);
}
} else {
complete(&mpc83xx_spi->done);
}
/* Clear the events */
mpc83xx_spi_write_reg(&mpc83xx_spi->base->event, event);
return ret;
}
static int __init mpc83xx_spi_probe(struct platform_device *dev)
{
struct spi_master *master;
struct mpc83xx_spi *mpc83xx_spi;
struct fsl_spi_platform_data *pdata;
struct resource *r;
u32 regval;
int ret = 0;
/* Get resources(memory, IRQ) associated with the device */
master = spi_alloc_master(&dev->dev, sizeof(struct mpc83xx_spi));
if (master == NULL) {
ret = -ENOMEM;
goto err;
}
platform_set_drvdata(dev, master);
pdata = dev->dev.platform_data;
if (pdata == NULL) {
ret = -ENODEV;
goto free_master;
}
r = platform_get_resource(dev, IORESOURCE_MEM, 0);
if (r == NULL) {
ret = -ENODEV;
goto free_master;
}
mpc83xx_spi = spi_master_get_devdata(master);
mpc83xx_spi->bitbang.master = spi_master_get(master);
mpc83xx_spi->bitbang.chipselect = mpc83xx_spi_chipselect;
mpc83xx_spi->bitbang.setup_transfer = mpc83xx_spi_setup_transfer;
mpc83xx_spi->bitbang.txrx_bufs = mpc83xx_spi_bufs;
mpc83xx_spi->activate_cs = pdata->activate_cs;
mpc83xx_spi->deactivate_cs = pdata->deactivate_cs;
mpc83xx_spi->qe_mode = pdata->qe_mode;
mpc83xx_spi->get_rx = mpc83xx_spi_rx_buf_u8;
mpc83xx_spi->get_tx = mpc83xx_spi_tx_buf_u8;
if (mpc83xx_spi->qe_mode)
mpc83xx_spi->spibrg = pdata->sysclk / 2;
else
mpc83xx_spi->spibrg = pdata->sysclk;
mpc83xx_spi->rx_shift = 0;
mpc83xx_spi->tx_shift = 0;
if (mpc83xx_spi->qe_mode) {
mpc83xx_spi->rx_shift = 16;
mpc83xx_spi->tx_shift = 24;
}
mpc83xx_spi->bitbang.master->setup = mpc83xx_spi_setup;
init_completion(&mpc83xx_spi->done);
mpc83xx_spi->base = ioremap(r->start, r->end - r->start + 1);
if (mpc83xx_spi->base == NULL) {
ret = -ENOMEM;
goto put_master;
}
mpc83xx_spi->irq = platform_get_irq(dev, 0);
if (mpc83xx_spi->irq < 0) {
ret = -ENXIO;
goto unmap_io;
}
/* Register for SPI Interrupt */
ret = request_irq(mpc83xx_spi->irq, mpc83xx_spi_irq,
0, "mpc83xx_spi", mpc83xx_spi);
if (ret != 0)
goto unmap_io;
master->bus_num = pdata->bus_num;
master->num_chipselect = pdata->max_chipselect;
/* SPI controller initializations */
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, 0);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mask, 0);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->command, 0);
mpc83xx_spi_write_reg(&mpc83xx_spi->base->event, 0xffffffff);
/* Enable SPI interface */
regval = pdata->initial_spmode | SPMODE_INIT_VAL | SPMODE_ENABLE;
if (pdata->qe_mode)
regval |= SPMODE_OP;
mpc83xx_spi_write_reg(&mpc83xx_spi->base->mode, regval);
ret = spi_bitbang_start(&mpc83xx_spi->bitbang);
if (ret != 0)
goto free_irq;
printk(KERN_INFO
"%s: MPC83xx SPI Controller driver at 0x%p (irq = %d)\n",
dev->dev.bus_id, mpc83xx_spi->base, mpc83xx_spi->irq);
return ret;
free_irq:
free_irq(mpc83xx_spi->irq, mpc83xx_spi);
unmap_io:
iounmap(mpc83xx_spi->base);
put_master:
spi_master_put(master);
free_master:
kfree(master);
err:
return ret;
}
static int __devexit mpc83xx_spi_remove(struct platform_device *dev)
{
struct mpc83xx_spi *mpc83xx_spi;
struct spi_master *master;
master = platform_get_drvdata(dev);
mpc83xx_spi = spi_master_get_devdata(master);
spi_bitbang_stop(&mpc83xx_spi->bitbang);
free_irq(mpc83xx_spi->irq, mpc83xx_spi);
iounmap(mpc83xx_spi->base);
spi_master_put(mpc83xx_spi->bitbang.master);
return 0;
}
static struct platform_driver mpc83xx_spi_driver = {
.probe = mpc83xx_spi_probe,
.remove = __devexit_p(mpc83xx_spi_remove),
.driver = {
.name = "mpc83xx_spi",
},
};
static int __init mpc83xx_spi_init(void)
{
return platform_driver_register(&mpc83xx_spi_driver);
}
static void __exit mpc83xx_spi_exit(void)
{
platform_driver_unregister(&mpc83xx_spi_driver);
}
module_init(mpc83xx_spi_init);
module_exit(mpc83xx_spi_exit);
MODULE_AUTHOR("Kumar Gala");
MODULE_DESCRIPTION("Simple MPC83xx SPI Driver");
MODULE_LICENSE("GPL");
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