Re: [PATCH] nios2: Add Altera SPI master driver

[Sascha Hauer <s.hauer@pengutronix.de>]

On Sat, Jul 30, 2011 at 10:18:23PM +0200, franck.jullien@gmail.com wrote:
> From: Franck Jullien <franck.jullien@gmail.com>
> 
> Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
> ---
>  arch/nios2/include/asm/spi.h |   21 ++++
>  drivers/spi/Kconfig          |    5 +
>  drivers/spi/Makefile         |    1 +
>  drivers/spi/altera_spi.c     |  226 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 253 insertions(+), 0 deletions(-)
>  create mode 100644 arch/nios2/include/asm/spi.h
>  create mode 100644 drivers/spi/altera_spi.c
> 
> diff --git a/arch/nios2/include/asm/spi.h b/arch/nios2/include/asm/spi.h
> new file mode 100644
> index 0000000..4e576b9
> --- /dev/null
> +++ b/arch/nios2/include/asm/spi.h
> @@ -0,0 +1,21 @@
> +#ifndef __ALTERA_SPI_H_
> +#define __ALTERA_SPI_H_
> +
> +#include <spi/spi.h>
> +
> +struct spi_altera_master {
> +	int	num_chipselect;
> +	int	spi_mode;
> +	int	databits;
> +	int	speed;
> +};
> +
> +struct altera_spi {
> +	struct spi_master	master;
> +	int			databits;
> +	int			speed;
> +	int			mode;
> +	void __iomem		*regs;
> +};
> +
> +#endif /*__ALTERA_SPI_H_*/
> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> index 9ab03f6..c72493c 100644
> --- a/drivers/spi/Kconfig
> +++ b/drivers/spi/Kconfig
> @@ -19,4 +19,9 @@ config DRIVER_SPI_IMX_2_3
>  	depends on ARCH_IMX51 || ARCH_IMX53
>  	default y
>  
> +config DRIVER_SPI_ALTERA
> +	bool "Altera SPI Master driver"
> +	depends on NIOS2
> +	depends on SPI
> +
>  endmenu
> diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
> index b2b2f67..90e141d 100644
> --- a/drivers/spi/Makefile
> +++ b/drivers/spi/Makefile
> @@ -1,2 +1,3 @@
>  obj-$(CONFIG_SPI) += spi.o
>  obj-$(CONFIG_DRIVER_SPI_IMX) += imx_spi.o
> +obj-$(CONFIG_DRIVER_SPI_ALTERA) += altera_spi.o
> diff --git a/drivers/spi/altera_spi.c b/drivers/spi/altera_spi.c
> new file mode 100644
> index 0000000..71df6b7
> --- /dev/null
> +++ b/drivers/spi/altera_spi.c
> @@ -0,0 +1,226 @@
> +/*
> + * (C) Copyright 2011 - Franck JULLIEN <elec4fun@gmail.com>
> + * Inspired from Thomas Chou's Linux spi_altera.c driver
> + *
> + * 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.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
> + * MA 02111-1307 USA
> + *
> + */
> +
> +#include <common.h>
> +#include <init.h>
> +#include <driver.h>
> +#include <spi/spi.h>
> +#include <asm/io.h>
> +#include <asm/spi.h>
> +#include <asm/nios2-io.h>
> +
> +#define CS_ACTIVE	1
> +#define CS_INACTIVE	0
> +
> +static int altera_spi_setup(struct spi_device *spi)
> +{
> +	struct spi_master *master = spi->master;
> +	struct device_d *master_dev = master->dev;
> +	struct device_d spi_dev = spi->dev;
> +	struct altera_spi *altera_spi = container_of(master, struct altera_spi, master);
> +
> +	if (spi->bits_per_word != altera_spi->databits) {
> +		printf("%s doesn't support %d bits per word requested by %s\n", master_dev->name,
> +			spi->bits_per_word, spi_dev.name);
> +		return -1;
> +	}
> +
> +	if ((spi->mode & (SPI_CPHA | SPI_CPOL)) != altera_spi->mode) {
> +		printf("%s doesn't support SPI_MODE%d requested by %s\n", master_dev->name,
> +			spi->mode & (SPI_CPHA | SPI_CPOL), spi_dev.name);
> +		return -1;
> +	}
> +
> +	if (spi->max_speed_hz < altera_spi->speed) {
> +		printf("%s frequency is too high for %s\n", master_dev->name, spi_dev.name);
> +		return -1;
> +	}
> +
> +	debug("%s mode 0x%08x bits_per_word: %d speed: %d\n",
> +			__func__, spi->mode, spi->bits_per_word,
> +			altera_spi->speed);
> +

Please use dev_info and friends for driver output.

> +	return 0;
> +}
> +
> +
> +static unsigned int altera_spi_xchg_single(struct altera_spi *altera_spi, unsigned int data)
> +{
> +	struct nios_spi *nios_spi = altera_spi->regs;
> +
> +	while (!(readl(&nios_spi->status) & NIOS_SPI_TRDY));
> +	writel(data, &nios_spi->txdata);
> +
> +	while (!(readl(&nios_spi->status) & NIOS_SPI_RRDY));
> +
> +	return readl(&nios_spi->rxdata);
> +}
> +
> +/*
> + * When using SPI_CS_HIGH devices, only one device is allowed to be
> + * connected to the Altera SPI master. This limitation is due to the
> + * emulation of an active high CS by writing 0 to the slaveselect register
> + * (this produce a '1' to all CS pins).
> + */
> +static void altera_spi_chipselect(struct spi_device *spi, int is_active)
> +{
> +	struct altera_spi *altera_spi = container_of(spi->master, struct altera_spi, master);
> +	struct nios_spi *nios_spi = altera_spi->regs;
> +	uint32_t tmp;
> +
> +	if (spi->mode & SPI_CS_HIGH) {
> +		switch (is_active) {
> +		case CS_INACTIVE:
> +			writel(1 << spi->chip_select, &nios_spi->slaveselect);
> +			tmp = readl(&nios_spi->control);
> +			writel(tmp | NIOS_SPI_SSO, &nios_spi->control);
> +			break;
> +
> +		case CS_ACTIVE:
> +			tmp = readw(&nios_spi->control);
> +			writew(tmp & ~NIOS_SPI_SSO, &nios_spi->control);
> +			writel(0, &nios_spi->slaveselect);
> +			break;
> +		}
> +	} else {
> +		switch (is_active) {
> +		case CS_INACTIVE:
> +			tmp = readw(&nios_spi->control);
> +			writew(tmp & ~NIOS_SPI_SSO, &nios_spi->control);
> +			break;
> +
> +		case CS_ACTIVE:
> +			writel(1 << spi->chip_select, &nios_spi->slaveselect);
> +			tmp = readl(&nios_spi->control);
> +			writel(tmp | NIOS_SPI_SSO, &nios_spi->control);
> +			break;
> +		}
> +	}
> +}

Better to split this code into two functions
(altera_spi_cs_active/inactive)


> +
> +static int altera_spi_transfer(struct spi_device *spi, struct spi_message *mesg)
> +{
> +	struct altera_spi *altera_spi = container_of(spi->master, struct altera_spi, master);
> +	struct nios_spi *nios_spi = altera_spi->regs;
> +	struct spi_transfer	*t = NULL;
> +	int word_len =  spi->bits_per_word;
> +
> +	u32 txval;
> +	u32 rxval;
> +
> +	altera_spi_chipselect(spi, 1);
> +
> +	word_len = spi->bits_per_word;
> +	mesg->actual_length = 0;
> +
> +	list_for_each_entry(t, &mesg->transfers, transfer_list) {
> +
> +		if (word_len <= 8) {
> +			const u8 *txbuf = t->tx_buf;
> +			u8 *rxbuf = t->rx_buf;
> +			int i = 0;
> +
> +			while (i < t->len) {
> +				txval = txbuf ? txbuf[i] : 0;
> +				rxval = altera_spi_xchg_single(altera_spi, txval);
> +				if (rxbuf)
> +					rxbuf[i] = rxval;
> +				i++;
> +				mesg->actual_length++;
> +			}
> +		} else if (word_len <= 16) {
> +			const u16 *txbuf = t->tx_buf;
> +			u16 *rxbuf = t->rx_buf;
> +			int i = 0;
> +
> +			while (i < t->len >> 1) {
> +				txval = txbuf ? txbuf[i] : 0;
> +				rxval = altera_spi_xchg_single(altera_spi, txval);
> +				if (rxbuf)
> +					rxbuf[i] = rxval;
> +				i++;
> +				mesg->actual_length += 2;
> +			}
> +		} else if (word_len <= 32) {
> +			const u32 *txbuf = t->tx_buf;
> +			u32 *rxbuf = t->rx_buf;
> +			int i = 0;
> +
> +			while (i < t->len >> 2) {
> +				txval = txbuf ? txbuf[i] : 0;
> +				rxval = altera_spi_xchg_single(altera_spi, txval);
> +				if (rxbuf)
> +					rxbuf[i] = rxval;
> +				i++;
> +				mesg->actual_length += 4;
> +			}

Can you please put the code inside this loop into a seperate function?
I can imagine that at some point we want to introduce a helper function
to the spi core which loops around the transfers of each message and does
the chipselect handling. Having this code in a seperate function now
makes it easier to convert to the helper later.

Sascha

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