Message-ID: <52CED586.7030602@overkiz.com>
Date:	Thu, 09 Jan 2014 17:59:50 +0100
From:	boris brezillon <b.brezillon@...rkiz.com>
To:	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	nicolas.ferre@...el.com, arnd@...db.de
CC:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/12] at91: dt: smc: Added smc bus driver

Hello JJ,

On 09/01/2014 13:31, Jean-Jacques Hiblot wrote:
> The EBI/SMC external interface is used to access external peripherals (NAND
> and Ethernet controller in the case of sam9261ek). Different configurations and
> timings are required for those peripherals. This bus driver can be used to
> setup the bus timings/configuration from the device tree.
> It currently accepts timings in clock period and in nanoseconds.
>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
> ---
>   drivers/memory/Kconfig     |  10 ++
>   drivers/memory/Makefile    |   1 +
>   drivers/memory/atmel-smc.c | 431 +++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 442 insertions(+)
>   create mode 100644 drivers/memory/atmel-smc.c
>
> diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
> index 29a11db..fbdfd63 100644
> --- a/drivers/memory/Kconfig
> +++ b/drivers/memory/Kconfig
> @@ -50,4 +50,14 @@ config TEGRA30_MC
>   	  analysis, especially for IOMMU/SMMU(System Memory Management
>   	  Unit) module.
>   
> +config ATMEL_SMC
> +	bool "Atmel SMC/EBI driver"
> +	default y
> +	depends on SOC_AT91SAM9 && OF
> +	help
> +	  Driver for Atmel SMC/EBI controller.
> +	  Used to configure the EBI (external bus interface) when the device-
> +	  tree is used. This bus supports NANDs, external ethernet controller,
> +	  SRAMs, ATA devices, etc.
> +
>   endif
> diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
> index 969d923..101abc4 100644
> --- a/drivers/memory/Makefile
> +++ b/drivers/memory/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_TI_EMIF)		+= emif.o
>   obj-$(CONFIG_MVEBU_DEVBUS)	+= mvebu-devbus.o
>   obj-$(CONFIG_TEGRA20_MC)	+= tegra20-mc.o
>   obj-$(CONFIG_TEGRA30_MC)	+= tegra30-mc.o
> +obj-$(CONFIG_ATMEL_SMC)        += atmel-smc.o
> diff --git a/drivers/memory/atmel-smc.c b/drivers/memory/atmel-smc.c
> new file mode 100644
> index 0000000..0a1d9ba
> --- /dev/null
> +++ b/drivers/memory/atmel-smc.c
> @@ -0,0 +1,431 @@
> +/*
> + * EBI driver for Atmel SAM9 chips
> + * inspired by the fsl weim bus driver
> + *
> + * Copyright (C) 2013 JJ Hiblot.
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +#include <linux/module.h>
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <linux/of_device.h>
> +#include <mach/at91sam9_smc.h>

You should avoid machine specific headers inclusions: we're trying to get
rid of them.

Duplicate the code and macros you need in your driver instead.

> +
> +struct  smc_data {
> +	struct clk *bus_clk;
> +	void __iomem *base;
> +	struct device *dev;
> +};
> +
> +struct at91_smc_devtype {
> +	unsigned int	cs_count;
> +};
> +
> +static const struct at91_smc_devtype sam9261_smc_devtype = {
> +	.cs_count	= 6,
> +};
> +
> +static const struct of_device_id smc_id_table[] = {
> +	{ .compatible = "atmel,at91sam9261-smc", .data = &sam9261_smc_devtype},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, smc_id_table);
> +
> +struct smc_parameters_type {
> +	const char *name;
> +	u16 width;
> +	u16 shift;
> +};
> +
> +static const struct smc_parameters_type smc_parameters[] = {
> +	{"smc,burst_size",	2, 28},
> +	{"smc,burst_enabled",	1, 24},
> +	{"smc,tdf_mode",	1, 20},
> +	{"smc,bus_width",	2, 12},
> +	{"smc,byte_access_type", 1,  8},
> +	{"smc,nwait_mode",	2,  4},
> +	{"smc,write_mode",	1,  0},
> +	{"smc,read_mode",	1,  1},
> +	{NULL}
> +};
> +
> +static int get_mode_register_from_dt(struct smc_data *smc,
> +				     struct device_node *np,
> +				     struct sam9_smc_config *cfg)
> +{
> +	int ret;
> +	u32 val;
> +	struct device *dev = smc->dev;
> +	const struct smc_parameters_type *p = smc_parameters;
> +	u32 mode = cfg->mode;
> +
> +	while (p->name) {
> +		ret = of_property_read_u32(np, p->name , &val);
> +		if (ret == -EINVAL) {
> +			dev_dbg(dev, "%s: property %s not set.\n", np->name,
> +				p->name);
> +			p++;
> +			continue;
> +		} else if (ret) {
> +			dev_err(dev, "%s: can't get property %s.\n", np->name,
> +				p->name);
> +			return ret;
> +		}
> +		if (val >= (1<<p->width)) {
> +			dev_err(dev, "%s: property %s out of range.\n",
> +				np->name, p->name);
> +			return -ERANGE;
> +		}
> +		mode &= ~(((1<<p->width)-1) << p->shift);
> +		mode |= (val << p->shift);
> +		p++;
> +	}
> +	cfg->mode = mode;
> +	return 0;
> +}
> +
> +static int generic_timing_from_dt(struct smc_data *smc, struct device_node *np,
> +				  struct sam9_smc_config *cfg)
> +{
> +	u32 val;
> +
> +	if (!of_property_read_u32(np, "smc,ncs_read_setup" , &val))
> +		cfg->ncs_read_setup = val;
> +
> +	if (!of_property_read_u32(np, "smc,nrd_setup" , &val))
> +		cfg->nrd_setup = val;
> +
> +	if (!of_property_read_u32(np, "smc,ncs_write_setup" , &val))
> +		cfg->ncs_write_setup = val;
> +
> +	if (!of_property_read_u32(np, "smc,nwe_setup" , &val))
> +		cfg->nwe_setup = val;
> +
> +	if (!of_property_read_u32(np, "smc,ncs_read_pulse" , &val))
> +		cfg->ncs_read_pulse = val;
> +
> +	if (!of_property_read_u32(np, "smc,nrd_pulse" , &val))
> +		cfg->nrd_pulse = val;
> +
> +	if (!of_property_read_u32(np, "smc,ncs_write_pulse" , &val))
> +		cfg->ncs_write_pulse = val;
> +
> +	if (!of_property_read_u32(np, "smc,nwe_pulse" , &val))
> +		cfg->nwe_pulse = val;
> +
> +	if (!of_property_read_u32(np, "smc,read_cycle" , &val))
> +		cfg->read_cycle = val;
> +
> +	if (!of_property_read_u32(np, "smc,write_cycle" , &val))
> +		cfg->write_cycle = val;
> +
> +	if (!of_property_read_u32(np, "smc,tdf_cycles" , &val))
> +		cfg->tdf_cycles = val;
> +
> +	return get_mode_register_from_dt(smc, np, cfg);
> +}
> +
> +/* convert the time in ns in a number of clock cycles */
> +static u32 ns_to_cycles(u32 ns, u32 clk)
> +{
> +	/*
> +	 * convert the clk to kHz for the rest of the calculation to avoid
> +	 * overflow
> +	 */
> +	u32 clk_kHz = clk / 1000;
> +	u32 ncycles = ((ns * clk_kHz) + 1000000 - 1) / 1000000;
What about using an u64 type and do_div ?
> +	return ncycles;
> +}
> +
> +static u32 cycles_to_coded_cycle(u32 cycles, int a, int b)
> +{
> +	u32 mask_high = (1 << a) - 1;
> +	u32 mask_low = (1 << b) - 1;
> +	u32 coded;
> +
> +	/* check if the value can be described with the coded format */
> +	if (cycles & (mask_high & ~mask_low)) {
> +		/* not representable. we need to round up */
> +		cycles |= mask_high;
> +		cycles += 1;
> +	}
> +	/* Now the value can be represented in the coded format */
> +	coded = (cycles & ~mask_high) >> (a - b);
> +	coded |= (cycles & mask_low);
> +	return coded;
> +}
> +
> +static u32 ns_to_rw_cycles(u32 ns, u32 clk)
> +{
> +	return cycles_to_coded_cycle(ns_to_cycles(ns, clk), 8, 7);
> +}
> +
> +static u32 ns_to_pulse_cycles(u32 ns, u32 clk)
> +{
> +	return cycles_to_coded_cycle(ns_to_cycles(ns, clk), 8, 6);
> +}
> +
> +static u32 ns_to_setup_cycles(u32 ns, u32 clk)
> +{
> +	return cycles_to_coded_cycle(ns_to_cycles(ns, clk), 7, 5);
> +}
> +
> +static u32 cycles_to_ns(u32 cycles, u32 clk)
> +{
> +	/*
> +	 * convert the clk to kHz for the rest of the calculation to avoid
> +	 * overflow
> +	 */
> +	u32 clk_kHz = clk / 1000;

Ditto (u64 + do_div).
> +	return (cycles * 1000000) / clk_kHz;
> +}
> +
> +static u32 coded_cycle_to_cycles(u32 coded, int a, int b)
> +{
> +	u32 cycles = (coded >> b) << a;
> +	u32 mask_low = (1 << b) - 1;
> +	cycles |= (coded & mask_low);
> +	return cycles;
> +}
> +
> +static u32 rw_cycles_to_ns(u32 reg, u32 clk)
> +{
> +	return cycles_to_ns(coded_cycle_to_cycles(reg, 8, 7), clk);
> +}
> +
> +static u32 pulse_cycles_to_ns(u32 reg, u32 clk)
> +{
> +	return cycles_to_ns(coded_cycle_to_cycles(reg, 8, 6), clk);
> +}
> +
> +static u32 setup_cycles_to_ns(u32 reg, u32 clk)
> +{
> +	return cycles_to_ns(coded_cycle_to_cycles(reg, 7, 5), clk);
> +}
> +
> +static void dump_timing(struct smc_data *smc, struct sam9_smc_config *config)
> +{
> +	u32 freq = clk_get_rate(smc->bus_clk);
> +	struct device *dev = smc->dev;
> +
> +#define DUMP(fn, y)	dev_info(dev, "%s : 0x%x (%d ns)\n", #y, config->y,\
> +				 fn(config->y, freq))
> +#define DUMP_PULSE(y)	DUMP(pulse_cycles_to_ns, y)
> +#define DUMP_RWCYCLE(y)	DUMP(rw_cycles_to_ns, y)
> +#define DUMP_SETUP(y)	DUMP(setup_cycles_to_ns, y)
> +#define DUMP_SIMPLE(y)	DUMP(cycles_to_ns, y)
> +
> +	DUMP_SETUP(nwe_setup);
> +	DUMP_SETUP(ncs_write_setup);
> +	DUMP_SETUP(nrd_setup);
> +	DUMP_SETUP(ncs_read_setup);
> +	DUMP_PULSE(nwe_pulse);
> +	DUMP_PULSE(ncs_write_pulse);
> +	DUMP_PULSE(nrd_pulse);
> +	DUMP_PULSE(ncs_read_pulse);
> +	DUMP_RWCYCLE(write_cycle);
> +	DUMP_RWCYCLE(read_cycle);
> +	DUMP_SIMPLE(tdf_cycles);
> +}
> +
> +static int ns_timing_from_dt(struct smc_data *smc, struct device_node *np,
> +			     struct sam9_smc_config *cfg)
> +{
> +	u32 t_ns;
> +	u32 freq = clk_get_rate(smc->bus_clk);
> +
> +	if (!of_property_read_u32(np, "smc,ncs_read_setup" , &t_ns))
> +		cfg->ncs_read_setup = ns_to_setup_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,nrd_setup" , &t_ns))
> +		cfg->nrd_setup = ns_to_setup_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,ncs_write_setup" , &t_ns))
> +		cfg->ncs_write_setup = ns_to_setup_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,nwe_setup" , &t_ns))
> +		cfg->nwe_setup = ns_to_setup_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,ncs_read_pulse" , &t_ns))
> +		cfg->ncs_read_pulse = ns_to_pulse_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,nrd_pulse" , &t_ns))
> +		cfg->nrd_pulse = ns_to_pulse_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,ncs_write_pulse" , &t_ns))
> +		cfg->ncs_write_pulse = ns_to_pulse_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,nwe_pulse" , &t_ns))
> +		cfg->nwe_pulse = ns_to_pulse_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,read_cycle" , &t_ns))
> +		cfg->read_cycle = ns_to_rw_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,write_cycle" , &t_ns))
> +		cfg->write_cycle = ns_to_rw_cycles(t_ns, freq);
> +
> +	if (!of_property_read_u32(np, "smc,tdf_cycles" , &t_ns))
> +		cfg->tdf_cycles = ns_to_cycles(t_ns, freq);
> +
> +	return get_mode_register_from_dt(smc, np, cfg);
> +}
> +
> +struct converter {
> +	const char *name;
> +	int (*fn) (struct smc_data *smc, struct device_node *np,
> +		   struct sam9_smc_config *cfg);
> +};
> +static const struct converter converters[] = {
> +	{"raw", generic_timing_from_dt},
> +	{"nanosec", ns_timing_from_dt},
> +};

Could you use more specific names like:
"atmel,smc-converter-generic"
"atmel,smc-converter-nand"
...

IMHO the timing unit should be specified in the property names:
smc,ncs_read_setup-ns
smc,ncs_read_setup-cycles



> +
> +/* Parse and set the timing for this device. */
> +static int smc_timing_setup(struct smc_data *smc, struct device_node *np,
> +		const struct at91_smc_devtype *devtype)
> +{
> +	int ret;
> +	u32 cs;
> +	int i;
> +	struct device *dev = smc->dev;
> +	const struct converter *converter;
> +	const char *converter_name = NULL;
> +	struct sam9_smc_config cfg;
> +
> +	ret = of_property_read_u32(np, "smc,cs" , &cs);

Shouldn't this be stored in the reg property ?
After all, in your DM9000 patch you use "@cs,offset" to identify the node...

> +	if (ret < 0) {
> +		dev_err(dev, "missing mandatory property : smc,cs\n");
> +		return ret;
> +	}
> +	if (cs >= devtype->cs_count) {
> +		dev_err(dev, "invalid value for property smc,cs (=%d)."
> +		"Must be in range 0 to %d\n", cs, devtype->cs_count-1);
> +		return -EINVAL;
> +	}
> +
> +	of_property_read_string(np, "smc,converter", &converter_name);

What about using the "compatible" property + struct of_device_id instead of
"smc,converter" property + struct converter ?

> +	if (converter_name) {
> +		for (i = 0; i < ARRAY_SIZE(converters); i++)
> +			if (strcmp(converters[i].name, converter_name) == 0)
> +				converter = &converters[i];
> +		if (!converter) {
> +			dev_info(dev, "unknown converter. aborting\n");
> +			return -EINVAL;
> +		}
> +	} else {
> +		dev_dbg(dev, "cs %d: no smc converter provided. using "
> +		"raw register values\n", cs);
> +		converter = &converters[0];
> +	}
> +	dev_dbg(dev, "cs %d using converter : %s\n", cs, converter->name);
> +	sam9_smc_cs_read(smc->base + (0x10 * cs), &cfg);
> +	converter->fn(smc, np, &cfg);
> +	ret = sam9_smc_check_cs_configuration(&cfg);
> +	if (ret < 0) {
> +		dev_info(dev, "invalid smc configuration for cs %d."
> +		"clipping values\n", cs);
> +		sam9_smc_clip_cs_configuration(&cfg);
> +		dump_timing(smc, &cfg);
> +	}
> +#ifdef DEBUG
> +	else
> +		dump_timing(smc, &cfg);
> +#endif

I'm not a big fan of #ifdef blocks inside the code.
You could define a dummy dump_timing function if DEBUG is not defined:

#ifdef DEBUG

static void dump_timing(struct smc_data *smc, struct sam9_smc_config 
*config)
{
     /* your implementation */
}

#else

static inline void dump_timing(struct smc_data *smc, struct 
sam9_smc_config *config)
{
}

#endif

Or just use dev_dbg when printing things in dump_timing.


> +
> +	sam9_smc_cs_configure(smc->base + (0x10 * cs), &cfg);
> +	return 0;
> +}
> +
> +static int smc_parse_dt(struct smc_data *smc)
> +{
> +	struct device *dev = smc->dev;
> +	const struct of_device_id *of_id = of_match_device(smc_id_table, dev);
> +	const struct at91_smc_devtype *devtype = of_id->data;
> +	struct device_node *child;
> +	int ret;
> +
> +	for_each_child_of_node(dev->of_node, child) {
> +		if (!child->name)
> +			continue;
> +		if (!of_device_is_available(child))
> +			continue;
> +		ret = smc_timing_setup(smc, child, devtype);
> +		if (ret) {
> +			static struct property status = {
> +				.name = "status",
> +				.value = "disabled",
> +				.length = sizeof("disabled"),
> +			};
> +			dev_err(dev, "%s set timing failed. This node will be disabled.\n",
> +				child->full_name);
> +			ret = of_update_property(child, &status);
> +			if (ret < 0) {
> +				dev_err(dev, "can't disable %s. aborting probe\n",
> +				child->full_name);
> +				break;

The concept of disabling the device if timings cannot be met sounds 
interresting...
Let's see what other maintainers say about this :).

> +			}
> +		}
> +	}
> +
> +	ret = of_platform_populate(dev->of_node, of_default_bus_match_table,
> +				   NULL, dev);
> +	if (ret)
> +		dev_err(dev, "%s fail to create devices.\n",
> +			dev->of_node->full_name);
> +
> +	return ret;
> +}
> +
> +static int smc_probe(struct platform_device *pdev)
> +{
> +	struct resource *res;
> +	int ret;
> +	void __iomem *base;
> +	struct clk *clk;
> +	struct smc_data *smc = devm_kzalloc(&pdev->dev, sizeof(struct smc_data),
> +					    GFP_KERNEL);
> +
> +	if (!smc)
> +		return -ENOMEM;
> +
> +	smc->dev = &pdev->dev;
> +
> +	/* get the resource */
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	base = devm_request_and_ioremap(&pdev->dev, res);
> +	if (IS_ERR(base)) {
> +		dev_err(&pdev->dev, "can't map SMC base address\n");
> +		return PTR_ERR(base);
> +	}
> +
> +	/* get the clock */
> +	clk = devm_clk_get(&pdev->dev, "smc");
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	smc->bus_clk = clk;
> +	smc->base = base;
> +
> +	/* parse the device node */
> +	ret = smc_parse_dt(smc);
> +	if (!ret)
> +		dev_info(&pdev->dev, "Driver registered.\n");
> +
> +	return ret;
> +}
> +
> +static struct platform_driver smc_driver = {
> +	.driver = {
> +		.name		= "atmel-smc",
> +		.owner		= THIS_MODULE,
> +		.of_match_table	= smc_id_table,
> +	},
> +};
> +module_platform_driver_probe(smc_driver, smc_probe);
> +
> +MODULE_AUTHOR("JJ Hiblot");
> +MODULE_DESCRIPTION("Atmel's SMC/EBI driver");
> +MODULE_LICENSE("GPL");


That's all for now. :)

I'll try to test it this week end on a sama5 board.

Best Regards,

Boris
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