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Date: Fri, 3 Jan 2014 10:42:23 +0100
From: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
To: boris brezillon <b.brezillon@...rkiz.com>
Cc: Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
nicolas.ferre@...el.com,
jean-jacques hiblot <jean-jacques.hiblot@...u.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/6] At91: dt: Added smc bus driver
2014/1/3 boris brezillon <b.brezillon@...rkiz.com>:
> On 31/12/2013 17:32, jjhiblot@...phandler.com wrote:
>>
>> From: jean-jacques hiblot <jean-jacques.hiblot@...u.com>
>>
>> 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.
>>
>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
>> ---
>> drivers/bus/Kconfig | 9 +++
>> drivers/bus/Makefile | 1 +
>> drivers/bus/atmel-smc.c | 182
>> ++++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 192 insertions(+)
>> create mode 100644 drivers/bus/atmel-smc.c
>>
>> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
>> index 552373c..8c944db5 100644
>> --- a/drivers/bus/Kconfig
>> +++ b/drivers/bus/Kconfig
>> @@ -12,6 +12,15 @@ config IMX_WEIM
>> The WEIM(Wireless External Interface Module) works like a bus.
>> You can attach many different devices on it, such as NOR,
>> onenand.
>>
>> +config ATMEL_SMC
>> + bool "Atmel SMC/EBI driver"
>> + 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.
>> +
>> config MVEBU_MBUS
>> bool
>> depends on PLAT_ORION
>> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
>> index 8947bdd..4364003 100644
>> --- a/drivers/bus/Makefile
>> +++ b/drivers/bus/Makefile
>> @@ -2,6 +2,7 @@
>> # Makefile for the bus drivers.
>> #
>>
>> +obj-$(CONFIG_ATMEL_SMC) += atmel-smc.o
>> obj-$(CONFIG_IMX_WEIM) += imx-weim.o
>> obj-$(CONFIG_MVEBU_MBUS) += mvebu-mbus.o
>> obj-$(CONFIG_OMAP_OCP2SCP) += omap-ocp2scp.o
>> diff --git a/drivers/bus/atmel-smc.c b/drivers/bus/atmel-smc.c
>> new file mode 100644
>> index 0000000..06e530d
>> --- /dev/null
>> +++ b/drivers/bus/atmel-smc.c
>> @@ -0,0 +1,182 @@
>> +/*
>> + * 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>
>> +
>> +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 reg;
>> + u16 width;
>> + u16 shift;
>> +};
>> +
>> +#define SETUP 0
>> +#define PULSE 1
>> +#define CYCLE 2
>> +#define MODE 3
>> +static const struct smc_parameters_type smc_parameters[] = {
>> + {"smc,ncs_read_setup", SETUP, 6, 24},
>> + {"smc,nrd_setup", SETUP, 6, 16},
>> + {"smc,ncs_write_setup", SETUP, 6, 8},
>> + {"smc,nwe_setup", SETUP, 6, 0},
>> + {"smc,ncs_read_pulse", PULSE, 6, 24},
>> + {"smc,nrd_pulse", PULSE, 6, 16},
>> + {"smc,ncs_write_pulse", PULSE, 6, 8},
>> + {"smc,nwe_pulse", PULSE, 6, 0},
>> + {"smc,read_cycle", CYCLE, 9, 16},
>> + {"smc,write_cycle", CYCLE, 9, 0},
>> + {"smc,burst_size", MODE, 2, 28},
>> + {"smc,burst_enabled", MODE, 1, 24},
>> + {"smc,tdf_mode", MODE, 1, 20},
>> + {"smc,tdf_cycles", MODE, 4, 16},
>> + {"smc,bus_width", MODE, 2, 12},
>> + {"smc,byte_access_type", MODE, 1, 8},
>> + {"smc,nwait_mode", MODE, 2, 4},
>> + {"smc,write_mode", MODE, 1, 0},
>> + {"smc,read_mode", MODE, 1, 1},
>> + {NULL}
>> +};
>> +
>> +/* Parse and set the timing for this device. */
>> +static int __init smc_timing_setup(struct device *dev, struct device_node
>> *np,
>> + void __iomem *base, const struct at91_smc_devtype
>> *devtype)
>> +{
>> + u32 val;
>> + int ret;
>> + u32 cs;
>> + const struct smc_parameters_type *p = smc_parameters;
>> + u32 shadow_smc_regs[5];
>> +
>> + ret = of_property_read_u32(np, "smc,cs" , &cs);
>> + if (ret < 0) {
>> + dev_err(dev, "missing mandatory property : smc,cs\n");
>> + return ret;
>> + }
>> + if (val >= 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;
>> + }
>> +
>> + /* set the timing for EBI */
>> + base += (0x10 * cs);
>> + shadow_smc_regs[SETUP] = readl_relaxed(base + AT91_SMC_SETUP);
>> + shadow_smc_regs[PULSE] = readl_relaxed(base + AT91_SMC_PULSE);
>> + shadow_smc_regs[CYCLE] = readl_relaxed(base + AT91_SMC_CYCLE);
>> + shadow_smc_regs[MODE] = readl_relaxed(base + AT91_SMC_MODE);
>> +
>> + while (p->name) {
>> + ret = of_property_read_u32(np, p->name , &val);
>> + if (ret == -EINVAL) {
>> + dev_dbg(dev, "cs %d: property %s not set.\n", cs,
>> + p->name);
>> + p++;
>> + continue;
>> + } else if (ret) {
>> + dev_err(dev, "cs %d: can't get property %s.\n",
>> cs,
>> + p->name);
>> + return ret;
>> + }
>> + if (val >= (1<<p->width)) {
>> + dev_err(dev, "cs %d: property %s out of range.\n",
>> cs,
>> + p->name);
>> + return -ERANGE;
>> + }
>> + shadow_smc_regs[p->reg] &= ~(((1<<p->width)-1) <<
>> p->shift);
>> + shadow_smc_regs[p->reg] |= (val << p->shift);
>> + p++;
>> + }
>> + writel_relaxed(shadow_smc_regs[SETUP], base + AT91_SMC_SETUP);
>> + writel_relaxed(shadow_smc_regs[PULSE], base + AT91_SMC_PULSE);
>> + writel_relaxed(shadow_smc_regs[CYCLE], base + AT91_SMC_CYCLE);
>> + writel_relaxed(shadow_smc_regs[MODE], base + AT91_SMC_MODE);
>> + return 0;
>> +}
>
>
> I think we should consider defining timings in nanoseconds instead of
> clk (actually master clk) cycles, because if we ever support master clk
> rate change (I hope so :)), then we won't be able to recalculate the
> appropriate timings (in cycles).
> Moreover this ease dt writer's work.
>
> tcycle calulation :
> mck_rate = clk_get_rate(mck);
> tcycle = (tns * 10^9) / mck_rate;
>
> dt binding:
>
> smc@xxx {
> clocks = <&mck>;
> dev@zz {
> smc,ncs_read_setup = <y>; /* in nsecs */
> ...
> };
> }
>
This is indeed something that could be done easily.
However I did this a few years ago for the EBI (and for another OS,
not linux) and it turned out to be not so magical. There were a lot of
side effects because most of the times the timings are defined (or at
least amended) empirically. There are also some cases when it's
easier to have the value in clock cycle (FPGA with synchronous IF)
I would be interested in the opinion of Nicolas in this matter.
>
> And what about defining a mechanism capable of handling several
> converter types (not just the generic one you described with the
> ncs, nrd, ... timings) ?
> For example NAND chip vendors use a common timing naming convention (tCLS,
> tCS, ...), and this is sometime annoying (and error-prone) to
> convert these timings into the SMC model.
>
> It would be great if we could define specific converters for these
> standardized protocols (NAND, NOR, ???).
>
> dt binding example:
>
> smc@xxx {
> clocks = <&mck>;
> ...
> dev@cs,offset {
> compatible = "atmel,at91-smc-generic-converter";
> smc,ncs_read_setup = <y>; /* in nsecs */
> ...
> };
>
> nand@cs,offset {
> compatible = "atmel,at91-smc-nand-converter";
> nand-chip {
> /* see atmel-nand dt binding */
> timings {
> tCLS = <..>;
> ...
> };
> /*
> * these timings are contained by the nand-chip
> * node because they describe the NAND timings
> * (as defined in many nand datasheets).
> */
> };
> };
> }
>
>
> These are just some thoughts, feel free to argue ;).
The idea is appealing. It could be done for NAND but I wonder if it
makes sense for the rest of the devices.
>
> Best Regards,
>
> Boris
>
>
>> +
>> +static int __init smc_parse_dt(struct platform_device *pdev,
>> + void __iomem *base)
>> +{
>> + struct device *dev = &pdev->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;
>> +
>> + ret = smc_timing_setup(dev, child, base, devtype);
>> + if (ret) {
>> + dev_err(dev, "%s set timing failed.\n",
>> + child->full_name);
>> + return ret;
>> + }
>> + }
>> +
>> + ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
>> + if (ret)
>> + dev_err(dev, "%s fail to create devices.\n",
>> + dev->of_node->full_name);
>> + return ret;
>> +}
>> +
>> +static int __init smc_probe(struct platform_device *pdev)
>> +{
>> + struct resource *res;
>> + void __iomem *base;
>> + int ret;
>> +
>> + /* 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);
>> + }
>> +
>> + /* parse the device node */
>> + ret = smc_parse_dt(pdev, base);
>> + 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");
>>
>
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