Message-ID: <20110120165430.GA24445@angua.secretlab.ca>
Date:	Thu, 20 Jan 2011 09:54:30 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Thomas Chou <thomas@...ron.com.tw>
Cc:	David Brownell <dbrownell@...rs.sourceforge.net>,
	linux-kernel@...r.kernel.org, nios2-dev@...c.et.ntust.edu.tw,
	devicetree-discuss@...ts.ozlabs.org,
	spi-devel-general@...ts.sourceforge.net,
	Mike Frysinger <vapier@...too.org>
Subject: Re: [PATCH v2] spi: add OpenCores tiny SPI driver

On Mon, Jan 17, 2011 at 03:32:22PM +0800, Thomas Chou wrote:
> This patch adds support of OpenCores tiny SPI driver.
> 
> http://opencores.org/project,tiny_spi
> 
> Signed-off-by: Thomas Chou <thomas@...ron.com.tw>
> ---
> v2 minor cleanup, same as Grant suggest for spi_altera.
> 
>  drivers/spi/Kconfig             |    6 +
>  drivers/spi/Makefile            |    1 +
>  drivers/spi/oc_tiny_spi.c       |  422 +++++++++++++++++++++++++++++++++++++++

Rename files to spi_oc_tiny.c

>  include/linux/spi/oc_tiny_spi.h |   14 ++
>  4 files changed, 443 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/spi/oc_tiny_spi.c
>  create mode 100644 include/linux/spi/oc_tiny_spi.h
> 
> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> index c58d81b..46a2ddc 100644
> --- a/drivers/spi/Kconfig
> +++ b/drivers/spi/Kconfig
> @@ -227,6 +227,12 @@ config SPI_FSL_ESPI
>  	  From MPC8536, 85xx platform uses the controller, and all P10xx,
>  	  P20xx, P30xx,P40xx, P50xx uses this controller.
>  
> +config SPI_OC_TINY_SPI
> +	tristate "OpenCores tiny SPI"
> +	select SPI_BITBANG
> +	help
> +	  This is the driver for OpenCores tiny SPI master controller.
> +
>  config SPI_OMAP_UWIRE
>  	tristate "OMAP1 MicroWire"
>  	depends on ARCH_OMAP1
> diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
> index 10e516a..6a2ae28 100644
> --- a/drivers/spi/Makefile
> +++ b/drivers/spi/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_SPI_GPIO)			+= spi_gpio.o
>  obj-$(CONFIG_SPI_IMX)			+= spi_imx.o
>  obj-$(CONFIG_SPI_LM70_LLP)		+= spi_lm70llp.o
>  obj-$(CONFIG_SPI_PXA2XX)		+= pxa2xx_spi.o
> +obj-$(CONFIG_SPI_OC_TINY_SPI)		+= oc_tiny_spi.o
>  obj-$(CONFIG_SPI_OMAP_UWIRE)		+= omap_uwire.o
>  obj-$(CONFIG_SPI_OMAP24XX)		+= omap2_mcspi.o
>  obj-$(CONFIG_SPI_OMAP_100K)		+= omap_spi_100k.o
> diff --git a/drivers/spi/oc_tiny_spi.c b/drivers/spi/oc_tiny_spi.c
> new file mode 100644
> index 0000000..ead7a09
> --- /dev/null
> +++ b/drivers/spi/oc_tiny_spi.c
> @@ -0,0 +1,422 @@
> +/*
> + * OpenCores tiny SPI master driver
> + *
> + * http://opencores.org/project,tiny_spi
> + *
> + * Copyright (C) 2011 Thomas Chou <thomas@...ron.com.tw>
> + *
> + * Based on spi_s3c24xx.c, which is:
> + * Copyright (c) 2006 Ben Dooks
> + * Copyright (c) 2006 Simtec Electronics
> + *	Ben Dooks <ben@...tec.co.uk>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/spinlock.h>
> +#include <linux/interrupt.h>
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/clk.h>
> +#include <linux/platform_device.h>
> +#include <linux/spi/spi.h>
> +#include <linux/spi/spi_bitbang.h>
> +#include <linux/spi/oc_tiny_spi.h>
> +#include <linux/io.h>
> +#include <linux/gpio.h>
> +#include <linux/of.h>
> +
> +#define DRV_NAME "oc_tiny_spi"
> +
> +#define TINY_SPI_RXDATA 0
> +#define TINY_SPI_TXDATA 4
> +#define TINY_SPI_STATUS 8
> +#define TINY_SPI_CONTROL 12
> +#define TINY_SPI_BAUD 16
> +
> +#define TINY_SPI_STATUS_TXE 0x1
> +#define TINY_SPI_STATUS_TXR 0x2
> +
> +struct tiny_spi {
> +	/* bitbang has to be first */
> +	struct spi_bitbang bitbang;
> +	struct completion done;
> +
> +	void __iomem *base;
> +	int irq;
> +	unsigned int freq;
> +	unsigned int baudwidth;
> +	unsigned int baud;
> +	unsigned int speed_hz;
> +	unsigned int mode;
> +	unsigned int len;
> +	unsigned int txc, rxc;
> +	const u8 *txp;
> +	u8 *rxp;
> +};
> +
> +static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
> +{
> +	return spi_master_get_devdata(sdev->master);
> +}
> +
> +static unsigned int tiny_spi_baud(struct spi_device *spi, unsigned int hz)
> +{
> +	struct tiny_spi *hw = tiny_spi_to_hw(spi);
> +
> +	return min(DIV_ROUND_UP(hw->freq, hz * 2), (1U << hw->baudwidth)) - 1;
> +}
> +
> +static void tiny_spi_chipselect(struct spi_device *spi, int is_active)
> +{
> +	gpio_set_value(spi->chip_select,
> +		       (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
> +}
> +
> +static int tiny_spi_setup_transfer(struct spi_device *spi,
> +				   struct spi_transfer *t)
> +{
> +	struct tiny_spi *hw = tiny_spi_to_hw(spi);
> +	unsigned int baud = hw->baud;
> +
> +	if (t) {
> +		if (t->speed_hz && t->speed_hz != hw->speed_hz)
> +			baud = tiny_spi_baud(spi, t->speed_hz);
> +	}
> +	writel(baud, hw->base + TINY_SPI_BAUD);
> +	writel(hw->mode, hw->base + TINY_SPI_CONTROL);
> +	return 0;
> +}
> +
> +static int tiny_spi_setup(struct spi_device *spi)
> +{
> +	struct tiny_spi *hw = tiny_spi_to_hw(spi);
> +
> +	if (spi->max_speed_hz != hw->speed_hz) {
> +		hw->speed_hz = spi->max_speed_hz;
> +		hw->baud = tiny_spi_baud(spi, hw->speed_hz);
> +	}
> +	hw->mode = spi->mode & (SPI_CPOL | SPI_CPHA);
> +	return 0;
> +}
> +
> +#ifndef CONFIG_TINY_SPI_IDLE_VAL
> +# define CONFIG_TINY_SPI_IDLE_VAL 0x00
> +#endif

Do you really want this as a Kconfig symbol?  Looks like something
that should be configured in pdata or the device tree.

> +
> +static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
> +{
> +	struct tiny_spi *hw = tiny_spi_to_hw(spi);
> +	const u8 *txp = t->tx_buf;
> +	u8 *rxp = t->rx_buf;
> +	unsigned int i;
> +
> +	if (hw->irq >= 0) {
> +		/* use intrrupt driven data transfer */
> +		hw->len = t->len;
> +		hw->txp = t->tx_buf;
> +		hw->rxp = t->rx_buf;
> +		hw->txc = 0;
> +		hw->rxc = 0;
> +		init_completion(&hw->done);
> +
> +		/* send the first byte */
> +		if (t->len > 1) {
> +			writeb(hw->txp ? *hw->txp++ : CONFIG_TINY_SPI_IDLE_VAL,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(hw->txp ? *hw->txp++ : CONFIG_TINY_SPI_IDLE_VAL,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
> +		} else {
> +			writeb(hw->txp ? *hw->txp++ : CONFIG_TINY_SPI_IDLE_VAL,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
> +		}
> +
> +		wait_for_completion(&hw->done);
> +	} else if (txp && rxp) {
> +		/* we need to tighten the transfer loop */
> +		writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +		if (t->len > 1) {
> +			writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i < t->len; i++) {
> +				u8 rx, tx = *txp++;
> +				while (!(readb(hw->base + TINY_SPI_STATUS) &
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				rx = readb(hw->base + TINY_SPI_TXDATA);
> +				writeb(tx, hw->base + TINY_SPI_TXDATA);
> +				*rxp++ = rx;
> +			}
> +			while (!(readb(hw->base + TINY_SPI_STATUS) &
> +				 TINY_SPI_STATUS_TXR))
> +				cpu_relax();
> +			*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS) &
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +		*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
> +	} else if (rxp) {
> +		writeb(CONFIG_TINY_SPI_IDLE_VAL, hw->base + TINY_SPI_TXDATA);
> +		if (t->len > 1) {
> +			writeb(CONFIG_TINY_SPI_IDLE_VAL,
> +			       hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i < t->len; i++) {
> +				u8 rx;
> +				while (!(readb(hw->base + TINY_SPI_STATUS) &
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				rx = readb(hw->base + TINY_SPI_TXDATA);
> +				writeb(CONFIG_TINY_SPI_IDLE_VAL,
> +				       hw->base + TINY_SPI_TXDATA);
> +				*rxp++ = rx;
> +			}
> +			while (!(readb(hw->base + TINY_SPI_STATUS) &
> +				 TINY_SPI_STATUS_TXR))
> +				cpu_relax();
> +			*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS) &
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +		*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
> +	} else if (txp) {
> +		writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +		if (t->len > 1) {
> +			writeb(*txp++, hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i < t->len; i++) {
> +				u8 tx = *txp++;
> +				while (!(readb(hw->base + TINY_SPI_STATUS) &
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				writeb(tx, hw->base + TINY_SPI_TXDATA);
> +			}
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS) &
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +	} else {
> +		writeb(CONFIG_TINY_SPI_IDLE_VAL, hw->base + TINY_SPI_TXDATA);
> +		if (t->len > 1) {
> +			writeb(CONFIG_TINY_SPI_IDLE_VAL,
> +			       hw->base + TINY_SPI_TXDATA);
> +			for (i = 2; i < t->len; i++) {
> +				while (!(readb(hw->base + TINY_SPI_STATUS) &
> +					 TINY_SPI_STATUS_TXR))
> +					cpu_relax();
> +				writeb(CONFIG_TINY_SPI_IDLE_VAL,
> +				       hw->base + TINY_SPI_TXDATA);
> +			}
> +		}
> +		while (!(readb(hw->base + TINY_SPI_STATUS) &
> +			 TINY_SPI_STATUS_TXE))
> +			cpu_relax();
> +	}
> +	return t->len;
> +}

I see a bunch of while loops in this function with no exit condition
if something goes badly with the hardware.  Also, this driver is going
to chew up *a lot* of cpu cycles when not using irqs.  Consider
putting the polled work into a tasklet instead of blindly spinning.
It will actually make the driver simpler because the irq and non-irq
cases become very similar.

> +
> +static irqreturn_t tiny_spi_irq(int irq, void *dev)
> +{
> +	struct tiny_spi *hw = dev;
> +
> +	writeb(0, hw->base + TINY_SPI_STATUS);
> +	if (hw->rxc + 1 == hw->len) {
> +		if (hw->rxp)
> +			*hw->rxp++ = readb(hw->base + TINY_SPI_RXDATA);
> +		hw->rxc++;
> +		complete(&hw->done);
> +	} else {
> +		if (hw->rxp)
> +			*hw->rxp++ = readb(hw->base + TINY_SPI_TXDATA);
> +		hw->rxc++;
> +		if (hw->txc < hw->len) {
> +			writeb(hw->txp ? *hw->txp++ : CONFIG_TINY_SPI_IDLE_VAL,
> +			       hw->base + TINY_SPI_TXDATA);
> +			hw->txc++;
> +			writeb(TINY_SPI_STATUS_TXR,
> +			       hw->base + TINY_SPI_STATUS);
> +		} else {
> +			writeb(TINY_SPI_STATUS_TXE,
> +			       hw->base + TINY_SPI_STATUS);
> +		}
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +#ifdef CONFIG_OF
> +static int __devinit tiny_spi_of_probe(struct platform_device *pdev,
> +				       struct tiny_spi *hw)
> +{
> +	const __be32 *val;
> +
> +	hw->bitbang.master->dev.of_node = pdev->dev.of_node;
> +	val = of_get_property(pdev->dev.of_node, "baud-width", NULL);

'baud-width'?

These properties need to be documented.  See below.

> +	if (val)
> +		hw->baudwidth = be32_to_cpup(val);
> +	val = of_get_property(pdev->dev.of_node, "clock-frequency", NULL);
> +	if (val)
> +		hw->freq = be32_to_cpup(val);
> +	return 0;
> +}
> +#else
> +static int __devinit tiny_spi_of_probe(struct platform_device *pdev,
> +				       struct tiny_spi *hw)
> +{
> +	return 0;
> +}
> +#endif
> +
> +static int __devinit tiny_spi_probe(struct platform_device *pdev)
> +{
> +	struct tiny_spi_platform_data *platp = pdev->dev.platform_data;
> +	struct tiny_spi *hw;
> +	struct spi_master *master;
> +	struct resource *res;
> +	int err = 0;
> +
> +	master = spi_alloc_master(&pdev->dev, sizeof(struct tiny_spi));
> +	if (master == NULL) {
> +		dev_err(&pdev->dev, "No memory for spi_master\n");
> +		err = -ENOMEM;
> +		goto err_no_mem;
> +	}
> +
> +	/* setup the master state. */
> +	master->bus_num = pdev->id;
> +	master->num_chipselect = 255;
> +	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
> +	master->setup = tiny_spi_setup;
> +
> +	hw = spi_master_get_devdata(master);
> +	platform_set_drvdata(pdev, hw);
> +
> +	/* setup the state for the bitbang driver */
> +	hw->bitbang.master = spi_master_get(master);
> +	if (hw->bitbang.master == NULL) {
> +		dev_err(&pdev->dev, "Cannot get device\n");
> +		err = -ENODEV;
> +		goto err_no_dev;
> +	}
> +	hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
> +	hw->bitbang.chipselect = tiny_spi_chipselect;
> +	hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;
> +
> +	/* find and map our resources */
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (res == NULL) {
> +		dev_err(&pdev->dev, "Cannot get IORESOURCE_MEM\n");
> +		err = -ENOENT;
> +		goto err_no_iores;
> +	}
> +	hw->base = ioremap(res->start, (res->end - res->start) + 1);
> +	if (hw->base == 0) {
> +		dev_err(&pdev->dev, "Cannot map IO\n");
> +		err = -ENXIO;
> +		goto err_no_iomap;
> +	}
> +	/* irq is optional */
> +	hw->irq = platform_get_irq(pdev, 0);
> +	if (hw->irq >= 0) {
> +		init_completion(&hw->done);
> +		err = request_irq(hw->irq, tiny_spi_irq, 0, pdev->name, hw);
> +		if (err) {
> +			dev_err(&pdev->dev, "Cannot claim IRQ\n");
> +			goto err_no_irq;
> +		}
> +	}
> +	/* find platform data */
> +	if (platp) {
> +		hw->freq = platp->freq;
> +		hw->baudwidth = platp->baudwidth;
> +	} else {
> +		err = tiny_spi_of_probe(pdev, hw);
> +		if (err)
> +			goto err_no_of;
> +	}
> +
> +	/* register our spi controller */
> +	err = spi_bitbang_start(&hw->bitbang);
> +	if (err) {
> +		dev_err(&pdev->dev, "Failed to register SPI master\n");
> +		goto err_register;
> +	}
> +	dev_info(&pdev->dev, "base %p, irq %d\n", hw->base, hw->irq);
> +
> +	return 0;
> +
> +err_register:
> +err_no_of:
> +	if (hw->irq >= 0)
> +		free_irq(hw->irq, hw);
> +err_no_irq:
> +	iounmap(hw->base);
> +err_no_iomap:
> +err_no_iores:
> +	spi_master_put(master);
> +err_no_mem:
> +err_no_dev:
> +	return err;
> +}
> +
> +static int __devexit tiny_spi_remove(struct platform_device *dev)
> +{
> +	struct tiny_spi *hw = platform_get_drvdata(dev);
> +	struct spi_master *master = hw->bitbang.master;
> +
> +	spi_bitbang_stop(&hw->bitbang);
> +
> +	if (hw->irq >= 0)
> +		free_irq(hw->irq, hw);
> +	iounmap(hw->base);
> +
> +	platform_set_drvdata(dev, NULL);
> +	spi_master_put(master);
> +	return 0;
> +}
> +
> +#ifdef CONFIG_OF
> +static struct of_device_id oc_tiny_spi_match[] = {
> +	{
> +		.compatible = "opencores,oc_tiny_spi",

If this is a soft core, then there should be a version number of some
sort on the compatible value.  Also, please use dash '-' instead of
underscore '_' in compatible values.  Also, for all of these new
bindings, they need to be documented.  Please add documentation to
Documentation/powerpc/dts-bindings (yes, I know, this is not
for powerpc, but that is the established directory.  I'll move it to a
better location soon).

Finally, one nitpick.  For conciseness, most of_device_id tables are
written in the form:

static struct of_device_id oc_tiny_spi_match[] = {
	{ .compatible = "opencores,oc_tiny_spi", }, },
	{},
}

> +MODULE_DEVICE_TABLE(of, oc_tiny_spi_match);
> +#endif
> +
> +static struct platform_driver tiny_spidrv = {
> +	.remove = __devexit_p(tiny_spi_remove),
> +	.driver = {
> +		.name = DRV_NAME,
> +		.owner = THIS_MODULE,
> +		.pm = NULL,
> +#ifdef CONFIG_OF
> +		.of_match_table = oc_tiny_spi_match,
> +#endif
> +	},
> +};
> +
> +static int __init tiny_spi_init(void)
> +{
> +	return platform_driver_probe(&tiny_spidrv, tiny_spi_probe);
> +}
> +module_init(tiny_spi_init);

Please use platform_driver_register, and put your probe function into
the platform_driver structure.

> +
> +static void __exit tiny_spi_exit(void)
> +{
> +	platform_driver_unregister(&tiny_spidrv);
> +}
> +module_exit(tiny_spi_exit);
> +
> +MODULE_DESCRIPTION("OpenCores tiny SPI driver");
> +MODULE_AUTHOR("Thomas Chou <thomas@...ron.com.tw>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:" DRV_NAME);
> diff --git a/include/linux/spi/oc_tiny_spi.h b/include/linux/spi/oc_tiny_spi.h
> new file mode 100644
> index 0000000..83de49d
> --- /dev/null
> +++ b/include/linux/spi/oc_tiny_spi.h
> @@ -0,0 +1,14 @@
> +#ifndef _LINUX_SPI_OC_TINY_SPI_H
> +#define _LINUX_SPI_OC_TINY_SPI_H
> +
> +/**
> + * struct tiny_spi_platform_data - platform data of the OpenCores tiny SPI
> + * @freq:	input clock freq to the core.
> + * @baudwidth:	baud rate divider width of the core.
> + */
> +struct tiny_spi_platform_data {
> +	uint freq;
> +	uint baudwidth;
> +};
> +
> +#endif /* _LINUX_SPI_OC_TINY_SPI_H */
> -- 
> 1.7.3.4
> 
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