Re: [PATCH v2 3/6] mtd: rawnand: add NVIDIA Tegra NAND Flash controller driver

[Stefan Agner <stefan@agner.ch>]

On 31.05.2018 11:37, Stefan Agner wrote:
> On 27.05.2018 23:54, Stefan Agner wrote:
>> Add support for the NAND flash controller found on NVIDIA
>> Tegra 2 SoCs. This implementation does not make use of the
>> command queue feature. Regular operations/data transfers are
>> done in PIO mode. Page read/writes with hardware ECC make
>> use of the DMA for data transfer.
>>
>> Signed-off-by: Lucas Stach <dev@lynxeye.de>
>> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> ---
>>  MAINTAINERS                       |   7 +
>>  drivers/mtd/nand/raw/Kconfig      |   6 +
>>  drivers/mtd/nand/raw/Makefile     |   1 +
>>  drivers/mtd/nand/raw/tegra_nand.c | 999 ++++++++++++++++++++++++++++++
>>  4 files changed, 1013 insertions(+)
>>  create mode 100644 drivers/mtd/nand/raw/tegra_nand.c
>>
> [...]
>> +
>> +	chip->ecc.read_page = tegra_nand_read_page_hwecc;
>> +	chip->ecc.write_page = tegra_nand_write_page_hwecc;
>> +	/* Not functional for unknown reason...
>> +	chip->ecc.read_page_raw = tegra_nand_read_page;
>> +	chip->ecc.write_page_raw = tegra_nand_write_page;
>> +	*/
> 
> I am giving up on these raw read/write_page functions. Using DMA without
> HW ECC just seems not to work.
> 
> I do not get the CMD_DONE interrupt as I do when using DMA with HW ECC.
> I tried with the same settings, just not enabling DMA (HW_ECC not set,
> HW_ERR_CORRECTION not set, and also with/without PIPELINE_EN).

s/not enabling DMA/not enabling HW ECC/

> 
> A register dump after a successful read with HW ECC looks like this:
> [  196.935199] CMD: 0x66890104
> [  196.938003] STATUS: 0x00000101
> [  196.941049] ISR: 0x00000000
> [  196.943865] CONFIG: 0x0084000b
> [  196.946914] DMA_MST_CTRL: 0x15000004
> [  196.950481] DMA_CFG_A: 0x00000fff
> [  196.954361] DMA_CFG_B: 0x00000000
> [  196.957670] FIFO: 0x0000aa00
> 
> Whereas without HW ECC completion times out (using
> wait_for_completion_timeout already):
> [  226.128618] tegra-nand 70008000.nand: CMD timeout, last CMD:
> 0xe6890104                              
> [  226.135375] CMD: 0xe6890104
> [  226.138201] STATUS: 0x00000100
> [  226.141280] ISR: 0x00000100
> [  226.153372] CONFIG: 0x0084000b
> [  226.156423] DMA_MST_CTRL: 0x95000004
> [  226.159989] DMA_CFG_A: 0x00000fff
> [  226.164084] DMA_CFG_B: 0x00000000
> [  226.167393] FIFO: 0x0000aa00
> 
> It looks to me as if the DMA just does not start the data cycle. The
> NAND seems to have read the page (RBSY0 is set).
> 
> 
> Note that it is never explicitly stated whether DMA without HW ECC is
> supported. There is some indication that it should: There are separated
> bits to enable HW ECC/DMA, the reference manual states "If HW ECC is
> enabled... " and a block diagram shows separate blocks for the ECC
> Engine and NAND DMA control.
> 
> There is also indication that it does not: The chapter Restrictions
> reads: "HW_ERR_CORRECTION = 0/1, doesn’t alter controller hardware
> behavior. Software error correction scheme with HW_ERR_CORRECTION = 0,
> is deprecated in Tegra 2 Processor."
> 
> Note that the default implementations nand_(read|write)_page_raw which
> use exec_op do work fine! Unfortunately, the PIO mode only allows 4
> bytes in a read cycle, hence raw read/write is slow...
> 
> --
> Stefan
> 
> 
>> +	config = readl(ctrl->regs + CFG);
>> +	config |= CFG_PIPE_EN | CFG_SKIP_SPARE | CFG_SKIP_SPARE_SIZE_4;
>> +
>> +	if (chip->options & NAND_BUSWIDTH_16)
>> +		config |= CFG_BUS_WIDTH_16;
>> +
>> +	switch (chip->ecc.algo) {
>> +	case NAND_ECC_RS:
>> +		bits_per_step = BITS_PER_STEP_RS * chip->ecc.strength;
>> +		mtd_set_ooblayout(mtd, &tegra_nand_oob_rs_ops);
>> +		switch (chip->ecc.strength) {
>> +		case 4:
>> +			config |= CFG_ECC_SEL | CFG_TVAL_4;
>> +			break;
>> +		case 6:
>> +			config |= CFG_ECC_SEL | CFG_TVAL_6;
>> +			break;
>> +		case 8:
>> +			config |= CFG_ECC_SEL | CFG_TVAL_8;
>> +			break;
>> +		default:
>> +			dev_err(dev, "ECC strength %d not supported\n",
>> +				chip->ecc.strength);
>> +			return -EINVAL;
>> +		}
>> +		break;
>> +	case NAND_ECC_BCH:
>> +		bits_per_step = BITS_PER_STEP_BCH * chip->ecc.strength;
>> +		mtd_set_ooblayout(mtd, &tegra_nand_oob_bch_ops);
>> +		switch (chip->ecc.strength) {
>> +		case 4:
>> +			bch_config = BCH_TVAL_4;
>> +			break;
>> +		case 8:
>> +			bch_config = BCH_TVAL_8;
>> +			break;
>> +		case 14:
>> +			bch_config = BCH_TVAL_14;
>> +			break;
>> +		case 16:
>> +			bch_config = BCH_TVAL_16;
>> +			break;
>> +		default:
>> +			dev_err(dev, "ECC strength %d not supported\n",
>> +				chip->ecc.strength);
>> +			return -EINVAL;
>> +		}
>> +		break;
>> +	default:
>> +		dev_err(dev, "ECC algorithm not supported\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	chip->ecc.bytes = DIV_ROUND_UP(bits_per_step, 8);
>> +
>> +	switch (mtd->writesize) {
>> +	case 256:
>> +		config |= CFG_PS_256;
>> +		break;
>> +	case 512:
>> +		config |= CFG_PS_512;
>> +		break;
>> +	case 1024:
>> +		config |= CFG_PS_1024;
>> +		break;
>> +	case 2048:
>> +		config |= CFG_PS_2048;
>> +		break;
>> +	case 4096:
>> +		config |= CFG_PS_4096;
>> +		break;
>> +	default:
>> +		dev_err(dev, "unhandled writesize %d\n", mtd->writesize);
>> +		return -ENODEV;
>> +	}
>> +
>> +	writel(config, ctrl->regs + CFG);
>> +	writel(bch_config, ctrl->regs + BCH_CONFIG);
>> +
>> +	err = nand_scan_tail(mtd);
>> +	if (err)
>> +		return err;
>> +
>> +	config |= CFG_TAG_BYTE_SIZE(mtd_ooblayout_count_freebytes(mtd) - 1);
>> +	writel(config, ctrl->regs + CFG);
>> +
>> +	err = mtd_device_register(mtd, NULL, 0);
>> +	if (err)
>> +		return err;
>> +
>> +	return 0;
>> +}
>> +
>> +static int tegra_nand_probe(struct platform_device *pdev)
>> +{
>> +	struct reset_control *rst;
>> +	struct tegra_nand_controller *ctrl;
>> +	struct resource *res;
>> +	unsigned long value;
>> +	int irq, err = 0;
>> +
>> +	ctrl = devm_kzalloc(&pdev->dev, sizeof(*ctrl), GFP_KERNEL);
>> +	if (!ctrl)
>> +		return -ENOMEM;
>> +
>> +	ctrl->dev = &pdev->dev;
>> +	nand_hw_control_init(&ctrl->controller);
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	ctrl->regs = devm_ioremap_resource(&pdev->dev, res);
>> +	if (IS_ERR(ctrl->regs))
>> +		return PTR_ERR(ctrl->regs);
>> +
>> +	rst = devm_reset_control_get(&pdev->dev, "nand");
>> +	if (IS_ERR(rst))
>> +		return PTR_ERR(rst);
>> +
>> +	ctrl->clk = devm_clk_get(&pdev->dev, "nand");
>> +	if (IS_ERR(ctrl->clk))
>> +		return PTR_ERR(ctrl->clk);
>> +
>> +	err = clk_prepare_enable(ctrl->clk);
>> +	if (err)
>> +		return err;
>> +
>> +	reset_control_reset(rst);
>> +
>> +	value = HWSTATUS_RDSTATUS_MASK(1) | HWSTATUS_RDSTATUS_VALUE(0) |
>> +		HWSTATUS_RBSY_MASK(NAND_STATUS_READY) |
>> +		HWSTATUS_RBSY_VALUE(NAND_STATUS_READY);
>> +	writel(NAND_CMD_STATUS, ctrl->regs + HWSTATUS_CMD);
>> +	writel(value, ctrl->regs + HWSTATUS_MASK);
>> +
>> +	init_completion(&ctrl->command_complete);
>> +	init_completion(&ctrl->dma_complete);
>> +
>> +	/* clear interrupts */
>> +	value = readl(ctrl->regs + ISR);
>> +	writel(value, ctrl->regs + ISR);
>> +
>> +	irq = platform_get_irq(pdev, 0);
>> +	err = devm_request_irq(&pdev->dev, irq, tegra_nand_irq, 0,
>> +			       dev_name(&pdev->dev), ctrl);
>> +	if (err)
>> +		goto err_disable_clk;
>> +
>> +	writel(DMA_CTRL_IS_DONE, ctrl->regs + DMA_CTRL);
>> +
>> +	/* enable interrupts */
>> +	value = IER_UND | IER_OVR | IER_CMD_DONE | IER_ECC_ERR | IER_GIE;
>> +	writel(value, ctrl->regs + IER);
>> +
>> +	/* reset config */
>> +	writel(0, ctrl->regs + CFG);
>> +
>> +	err = tegra_nand_chips_init(ctrl->dev, ctrl);
>> +	if (err)
>> +		goto err_disable_clk;
>> +
>> +	platform_set_drvdata(pdev, ctrl);
>> +
>> +	return 0;
>> +
>> +err_disable_clk:
>> +	clk_disable_unprepare(ctrl->clk);
>> +	return err;
>> +}
>> +
>> +static int tegra_nand_remove(struct platform_device *pdev)
>> +{
>> +	struct tegra_nand_controller *ctrl = platform_get_drvdata(pdev);
>> +
>> +	nand_release(nand_to_mtd(ctrl->chip));
>> +
>> +	clk_disable_unprepare(ctrl->clk);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id tegra_nand_of_match[] = {
>> +	{ .compatible = "nvidia,tegra20-nand" },
>> +	{ /* sentinel */ }
>> +};
>> +
>> +static struct platform_driver tegra_nand_driver = {
>> +	.driver = {
>> +		.name = "tegra-nand",
>> +		.of_match_table = tegra_nand_of_match,
>> +	},
>> +	.probe = tegra_nand_probe,
>> +	.remove = tegra_nand_remove,
>> +};
>> +module_platform_driver(tegra_nand_driver);
>> +
>> +MODULE_DESCRIPTION("NVIDIA Tegra NAND driver");
>> +MODULE_AUTHOR("Thierry Reding <thierry.reding@nvidia.com>");
>> +MODULE_AUTHOR("Lucas Stach <dev@lynxeye.de>");
>> +MODULE_AUTHOR("Stefan Agner <stefan@agner.ch>");
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_DEVICE_TABLE(of, tegra_nand_of_match);