Subject: [PATCHv9 1/3] mfd: altera: Add Altera SDRAM Controller

From: [email-masked] (Thor Thayer)
Date: Thu, 31 Jul 2014 15:00:50 -0500

On 07/31/2014 03:26 AM, Lee Jones wrote:
> On Wed, 30 Jul 2014, tthayer at opensource.altera.com wrote:
>
>> From: Thor Thayer <[email-masked]>
>>
>> Add a simple MFD for the Altera SDRAM Controller.
>>
>> Signed-off-by: Alan Tull <[email-masked]>
>> Signed-off-by: Thor Thayer <[email-masked]>
>> ---
>> v1-8: The MFD implementation was not included in the original series.
>>
>> v9: New MFD implementation.
>> ---
>>   MAINTAINERS                    |    5 ++
>>   drivers/mfd/Kconfig            |    7 ++
>>   drivers/mfd/Makefile           |    1 +
>>   drivers/mfd/altera-sdr.c       |  162 ++++++++++++++++++++++++++++++++++++++++
>>   include/linux/mfd/altera-sdr.h |  102 +++++++++++++++++++++++++
>>   5 files changed, 277 insertions(+)
>>   create mode 100644 drivers/mfd/altera-sdr.c
>>   create mode 100644 include/linux/mfd/altera-sdr.h
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 86efa7e..48a8923 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -1340,6 +1340,11 @@ M:	Dinh Nguyen <[email-masked]>
>>   S:	Maintained
>>   F:	drivers/clk/socfpga/
>>   
>> +ARM/SOCFPGA SDRAM CONTROLLER SUPPORT
>> +M:	Thor Thayer <[email-masked]>
>> +S:	Maintained
>> +F:	drivers/mfd/altera-sdr.c
>> +
>>   ARM/STI ARCHITECTURE
>>   M:	Srinivas Kandagatla <[email-masked]>
>>   M:	Maxime Coquelin <[email-masked]>
> This should be in a separate patch.
OK. Thanks for your comments and for reviewing. I will move this into a 
separate patch.
>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>> index 6cc4b6a..8ce4961 100644
>> --- a/drivers/mfd/Kconfig
>> +++ b/drivers/mfd/Kconfig
>> @@ -719,6 +719,13 @@ config MFD_STMPE
>>   		Keypad: stmpe-keypad
>>   		Touchscreen: stmpe-ts
>>   
>> +config MFD_ALTERA_SDR
>> +	bool "Altera SDRAM Controller MFD"
>> +	depends on ARCH_SOCFPGA
>> +	select MFD_CORE
>> +	help
>> +	  Support for Altera SDRAM Controller (SDR) MFD.
>> +
>>   menu "STMicroelectronics STMPE Interface Drivers"
>>   depends on MFD_STMPE
>>   
>> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
>> index 8afedba..24cc2b7 100644
>> --- a/drivers/mfd/Makefile
>> +++ b/drivers/mfd/Makefile
>> @@ -169,3 +169,4 @@ obj-$(CONFIG_MFD_AS3711)	+= as3711.o
>>   obj-$(CONFIG_MFD_AS3722)	+= as3722.o
>>   obj-$(CONFIG_MFD_STW481X)	+= stw481x.o
>>   obj-$(CONFIG_MFD_IPAQ_MICRO)	+= ipaq-micro.o
>> +obj-$(CONFIG_MFD_ALTERA_SDR)	+= altera-sdr.o
>> diff --git a/drivers/mfd/altera-sdr.c b/drivers/mfd/altera-sdr.c
>> new file mode 100644
>> index 0000000..b5c6646
>> --- /dev/null
>> +++ b/drivers/mfd/altera-sdr.c
>> @@ -0,0 +1,162 @@
>> +/*
>> + * SDRAM Controller (SDR) MFD
>> + *
>> + * Copyright (C) 2014 Altera Corporation
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.
> Can you use the shorter version of the licence?
Hi. This seems to be the shorter version of the license agreement and is 
fairly common in the kernel, right?
>> + */
> '\n' here.
OK.
>> +#include <linux/io.h>
>> +#include <linux/kernel.h>
>> +#include <linux/mfd/altera-sdr.h>
>> +#include <linux/mfd/core.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +
>> +static const struct mfd_cell altera_sdr_devs[] = {
>> +#if defined(CONFIG_EDAC_ALTERA_MC)
> No need to do this, as it will only be matched if the driver is
> enabled.  Please remove the #iffery.
OK. Will remove.
>> +	{
>> +		.name = "altr_sdram_edac",
>> +		.of_compatible = "altr,sdram-edac",
> What other devices will there be?
>
There will be an FPGA bridge and a power control driver that will need 
access to the SDR Controller registers.
>> +	},
>> +#endif
>> +};
>> +
>> +u32 altera_sdr_readl(struct altera_sdr *sdr, u32 reg_offset)
>> +{
>> +	return readl(sdr->reg_base + reg_offset);
>> +}
>> +EXPORT_SYMBOL_GPL(altera_sdr_readl);
>> +
>> +void altera_sdr_writel(struct altera_sdr *sdr, u32 reg_offset, u32 value)
>> +{
>> +	writel(value, sdr->reg_base + reg_offset);
>> +}
>> +EXPORT_SYMBOL_GPL(altera_sdr_writel);
> Why are you abstracting these?
>
> Might be better to use Regmap even.
regmap seems unnecessarily complex for what we're doing which is why 
this method was chosen.

Future drivers will access different sets of registers in the device. 
These drivers won't share bitfields in the same register so the MFD 
seemed like the best solution. Originally we implemented this using 
syscon but that seems to be frowned upon so we changed to using a MFD.
>> +/* Get total memory size in bytes */
>> +u32 altera_sdr_mem_size(struct altera_sdr *sdr)
>> +{
>> +	u32 size;
>> +	u32 read_reg, row, bank, col, cs, width;
> Weird that size is on its own.  Either place on a single line or
> separate them all.
OK. I will change this.
>> +	read_reg = altera_sdr_readl(sdr, SDR_DRAMADDRW_OFST);
>> +	if (read_reg < 0)
>> +		return 0;
>> +
>> +	width = altera_sdr_readl(sdr, SDR_DRAMIFWIDTH_OFST);
>> +	if (width < 0)
>> +		return 0;
>> +
>> +	col = (read_reg & SDR_DRAMADDRW_COLBITS_MASK) >>
>> +		SDR_DRAMADDRW_COLBITS_LSB;
>> +	row = (read_reg & SDR_DRAMADDRW_ROWBITS_MASK) >>
>> +		SDR_DRAMADDRW_ROWBITS_LSB;
>> +	bank = (read_reg & SDR_DRAMADDRW_BANKBITS_MASK) >>
>> +		SDR_DRAMADDRW_BANKBITS_LSB;
>> +	cs = (read_reg & SDR_DRAMADDRW_CSBITS_MASK) >>
>> +		SDR_DRAMADDRW_CSBITS_LSB;
> These would probably be better as macros.
>
OK. I will fix this.
>> +	/* Correct for ECC as its not addressible */
>> +	if (width == SDR_DRAMIFWIDTH_32B_ECC)
>> +		width = 32;
>> +	if (width == SDR_DRAMIFWIDTH_16B_ECC)
>> +		width = 16;
>> +
>> +	/* calculate the SDRAM size base on this info */
>> +	size = 1 << (row + bank + col);
>> +	size = size * cs * (width / 8);
>> +	return size;
>> +}
>> +EXPORT_SYMBOL_GPL(altera_sdr_mem_size);
> Should this really be done in here?  Isn't this an SDRAM function?
>
This register is part of the SDRAM controller and size information may 
be required by the other drivers that share this memory area/need SDRAM 
information.

>> +static int altera_sdr_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct altera_sdr *sdr;
>> +	struct resource *res;
>> +	void __iomem *base;
>> +	int ret;
>> +
>> +	sdr = devm_kzalloc(dev, sizeof(*sdr), GFP_KERNEL);
>> +	if (!sdr)
>> +		return -ENOMEM;
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	if (!res)
>> +		return -ENOENT;
>> +
>> +	base = devm_ioremap(dev, res->start, resource_size(res));
> Instead use devm_ioremap_resource(), then you can omit the error
> checking of platform_get_resource().
OK. Thanks. I will make the change.
>> +	if (!base)
>> +		return -ENOMEM;
>> +
>> +	sdr->dev = &pdev->dev;
> Either use 'dev' here, or remove the top line in this function and use
> &pdev->dev everywhere.  I personally prefer the latter.
OK. I will use the latter.
>> +	sdr->reg_base = base;
>> +
>> +	ret = mfd_add_devices(sdr->dev, 0, altera_sdr_devs,
>> +			      ARRAY_SIZE(altera_sdr_devs), NULL, 0, NULL);
>> +	if (ret)
>> +		dev_err(sdr->dev, "error adding devices");
>> +
>> +	platform_set_drvdata(pdev, sdr);
>> +
>> +	dev_dbg(dev, "Altera SDR MFD registered\n");
>> +
>> +	return 0;
>> +}
>> +
>> +static int altera_sdr_remove(struct platform_device *pdev)
>> +{
>> +	struct altera_sdr *sdr = platform_get_drvdata(pdev);
> No need for this, just use &pdev->dev.
OK. I will make the change.
>> +	mfd_remove_devices(sdr->dev);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id of_altera_sdr_match[] = {
>> +	{ .compatible = "altr,sdr", },
>> +	{ },
>> +};
>> +
>> +static const struct platform_device_id altera_sdr_ids[] = {
>> +	{ "altera_sdr", },
>> +	{ }
>> +};
> What's this for?
We don't strictly need it because we are driven by the device tree. It 
can be removed it if is a problem but I'm not clear why it is a problem.
>> +static struct platform_driver altera_sdr_driver = {
>> +	.driver = {
>> +		.name = "altera_sdr",
>> +		.owner = THIS_MODULE,
> You can remove this line, it's taken care of for you.
I will remove the .owner line.
>> +		.of_match_table = of_altera_sdr_match,
>> +	},
>> +	.probe		= altera_sdr_probe,
>> +	.remove		= altera_sdr_remove,
>> +	.id_table	= altera_sdr_ids,
>> +};
>> +
>> +static int __init altera_sdr_init(void)
>> +{
>> +	return platform_driver_register(&altera_sdr_driver);
>> +}
>> +postcore_initcall(altera_sdr_init);
> Why was this chosen?
We want this to happen pretty early.
>> +static void __exit altera_sdr_exit(void)
>> +{
>> +	platform_driver_unregister(&altera_sdr_driver);
>> +}
>> +module_exit(altera_sdr_exit);
>> +
>> +MODULE_AUTHOR("Alan Tull <[email-masked]>");
>> +MODULE_DESCRIPTION("Altera SDRAM Controller (SDR) MFD");
>> +MODULE_LICENSE("GPL v2");
>> diff --git a/include/linux/mfd/altera-sdr.h b/include/linux/mfd/altera-sdr.h
>> new file mode 100644
>> index 0000000..a5f5c39
>> --- /dev/null
>> +++ b/include/linux/mfd/altera-sdr.h
>> @@ -0,0 +1,102 @@
>> +/*
>> + * Copyright (C) 2014 Altera Corporation
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.
> Use the short version.
Same as above. This is the shorter version that we've been using at Altera.
>> + */
> '\n' here.
OK.
>> +#ifndef __LINUX_MFD_ALTERA_SDR_H
>> +#define __LINUX_MFD_ALTERA_SDR_H
>> +
>> +/* SDRAM Controller register offsets */
>> +#define SDR_CTLCFG_OFST                 0x00
>> +#define SDR_DRAMADDRW_OFST		0x2C
>> +#define SDR_DRAMIFWIDTH_OFST		0x30
>> +#define SDR_DRAMSTS_OFST                0x38
>> +#define SDR_DRAMINTR_OFST               0x3C
>> +#define SDR_SBECOUNT_OFST               0x40
>> +#define SDR_DBECOUNT_OFST               0x44
>> +#define SDR_ERRADDR_OFST                0x48
>> +#define SDR_DROPCOUNT_OFST              0x4C
>> +#define SDR_DROPADDR_OFST               0x50
>> +#define SDR_CTRLGRP_LOWPWREQ_OFST       0x54
>> +#define SDR_CTRLGRP_LOWPWRACK_OFST      0x58
>> +
>> +/* SDRAM Controller CtrlCfg Register Bit Masks */
>> +#define SDR_CTLCFG_ECC_EN               0x400
>> +#define SDR_CTLCFG_ECC_CORR_EN          0x800
>> +#define SDR_CTLCFG_GEN_SB_ERR           0x2000
>> +#define SDR_CTLCFG_GEN_DB_ERR           0x4000
>> +
>> +#define SDR_CTLCFG_ECC_AUTO_EN          (SDR_CTLCFG_ECC_EN | \
>> +					 SDR_CTLCFG_ECC_CORR_EN)
>> +
>> +/* SDRAM Controller Address Widths Field Register */
>> +#define SDR_DRAMADDRW_COLBITS_MASK      0x001F
>> +#define SDR_DRAMADDRW_COLBITS_LSB       0
>> +#define SDR_DRAMADDRW_ROWBITS_MASK      0x03E0
>> +#define SDR_DRAMADDRW_ROWBITS_LSB       5
>> +#define SDR_DRAMADDRW_BANKBITS_MASK     0x1C00
>> +#define SDR_DRAMADDRW_BANKBITS_LSB      10
>> +#define SDR_DRAMADDRW_CSBITS_MASK       0xE000
>> +#define SDR_DRAMADDRW_CSBITS_LSB        13
> We normally call _LSB, _SHIFT.
OK. I will change.
>> +/* SDRAM Controller Interface Data Width Defines */
>> +#define SDR_DRAMIFWIDTH_16B_ECC         24
>> +#define SDR_DRAMIFWIDTH_32B_ECC         40
>> +
>> +/* SDRAM Controller DRAM Status Register Bit Masks */
>> +#define SDR_DRAMSTS_SBEERR              0x04
>> +#define SDR_DRAMSTS_DBEERR              0x08
>> +#define SDR_DRAMSTS_CORR_DROP           0x10
>> +
>> +/* SDRAM Controller DRAM IRQ Register Bit Masks */
>> +#define SDR_DRAMINTR_INTREN             0x01
>> +#define SDR_DRAMINTR_SBEMASK            0x02
>> +#define SDR_DRAMINTR_DBEMASK            0x04
>> +#define SDR_DRAMINTR_CORRDROPMASK       0x08
>> +#define SDR_DRAMINTR_INTRCLR            0x10
>> +
>> +/* SDRAM Controller Single Bit Error Count Register Bit Masks */
>> +#define SDR_SBECOUNT_COUNT_MASK         0x0F
>> +
>> +/* SDRAM Controller Double Bit Error Count Register Bit Masks */
>> +#define SDR_DBECOUNT_COUNT_MASK         0x0F
>> +
>> +/* SDRAM Controller ECC Error Address Register Bit Masks */
>> +#define SDR_ERRADDR_ADDR_MASK           0xFFFFFFFF
>> +
>> +/* SDRAM Controller ECC Autocorrect Drop Count Register Bit Masks */
>> +#define SDR_DROPCOUNT_CORRMASK          0x0F
>> +
>> +/* SDRAM Controller ECC AutoCorrect Error Address Register Bit Masks */
>> +#define SDR_DROPADDR_ADDR_MASK          0xFFFFFFFF
>> +
>> +#define SELFRSHREQ_POS                  3
>> +#define SELFRSHREQ_MASK                 0x8
>> +
>> +#define SELFRFSHMASK_POS                4
>> +#define SELFRFSHMASK_MASK               0x30
>> +
>> +#define SELFRFSHACK_POS                 1
>> +#define SELFRFSHACK_MASK                0x2
>> +
>> +struct altera_sdr {
>> +	struct device *dev;
>> +	void __iomem *reg_base;
>> +};
>> +
>> +/* Register access API */
>> +u32 altera_sdr_readl(struct altera_sdr *sdr, u32 reg_offset);
>> +void altera_sdr_writel(struct altera_sdr *sdr, u32 reg_offset, u32 value);
> Regmap?
Same as above. This seems to be more complex than we need.

Thanks for your comments and for reviewing!

Thor
>> +u32 altera_sdr_mem_size(struct altera_sdr *sdr);
>> +
>> +#endif /* __LINUX_MFD_ALTERA_SDR_H */