RE: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support for Arasan NAND Flash Controller

[Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>]

Hi Boris,

> -----Original Message-----
> From: Boris Brezillon [mailto:boris.brezillon@xxxxxxxxxxx]
> Sent: Friday, November 9, 2018 1:38 PM
> To: Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>
> Cc: miquel.raynal@xxxxxxxxxxx; richard@xxxxxx; dwmw2@xxxxxxxxxxxxx;
> computersforpeace@xxxxxxxxx; marek.vasut@xxxxxxxxx; Michal Simek
> <michals@xxxxxxxxxx>; linux-mtd@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> nagasuresh12@xxxxxxxxx; robh@xxxxxxxxxx
> Subject: Re: [LINUX PATCH v12 3/3] mtd: rawnand: arasan: Add support for Arasan NAND
> Flash Controller
> 
> Hi Naga,
> 
> Just a preliminary review. I still think we have problems with how you execute NAND
> operations. You seem to assume that read/write operation are always page write/read operation
> with a size aligned on a page size. This is wrong, either the controller is able to execute the
> exact operation that has been requested or it returns -ENOTSUPP.
Are you pointing the anfc_read_param_get_feature_sp_read_type_exec()?
Where I am reading a length of page size even for get_features op.
Is that you are pointing?

> 
> On Fri, 9 Nov 2018 10:30:41 +0530
> Naga Sureshkumar Relli <naga.sureshkumar.relli@xxxxxxxxxx> wrote:
> 
> > +
> > +/**
> > + * struct anfc_nand_chip - Defines the nand chip related information
> > + * @node:		Used to store NAND chips into a list.
> > + * @chip:		NAND chip information structure.
> > + * @strength:		Bch or Hamming mode enable/disable.
> 
> The name is still confusing. BTW, can't you deduce Hamming vs BCH from the strength?
> Hamming strength is 1, while BCH strengths seem to start at 4.
Yes we can deduce. I will try that.
.
> 
> > + * @ecc_strength:	Ecc strength 4.8/12/16.
> 
> 				      ^/
> 
> > + * @eccval:		Ecc config value.
> > + * @spare_caddr_cycles:	Column address cycle information for spare area.
> > + * @pktsize:		Packet size for read / write operation.
> > + * @csnum:		chipselect number to be used.
> > + * @spktsize:		Packet size in ddr mode for status operation.
> > + * @inftimeval:		Data interface and timing mode information
> > + */
> > +struct anfc_nand_chip {
> > +	struct list_head node;
> > +	struct nand_chip chip;
> > +	bool strength;
> > +	u32 ecc_strength;
> > +	u32 eccval;
> > +	u16 spare_caddr_cycles;
> > +	u32 pktsize;
> > +	int csnum;
> > +	u32 spktsize;
> > +	u32 inftimeval;
> > +};
> > +
> > +/**
> > + * struct anfc_nand_controller - Defines the Arasan NAND flash controller
> > + *				 driver instance
> > + * @controller:		base controller structure.
> > + * @chips:		list of all nand chips attached to the ctrler.
> > + * @dev:		Pointer to the device structure.
> > + * @base:		Virtual address of the NAND flash device.
> > + * @clk_sys:		Pointer to the system clock.
> > + * @clk_flash:		Pointer to the flash clock.
> > + * @dma:		Dma enable/disable.
> > + * @buf:		Buffer used for read/write byte operations.
> > + * @irq:		irq number
> 
> You should need this field. Just get the irq num in you probe path an register an irq handler
> with devm_request_irq().
You mean to say, instead of putting irq in anfc_nand_controller structure, update the code like below snippet, right?

irq = platform_get_irq(pdev, 0);
if (irq < 0) {
            dev_err(dev, "failed to retrieve irq\n");
            return irq;
}
devm_request_irq(&pdev->dev, irq, anfc_irq_handler, 0, "arasannfc", nfc);

> 
> > + * @bufshift:		Variable used for indexing buffer operation
> > + * @csnum:		Chip select number currently inuse.
> 
> 						     ^ in use
> 
> > + * @event:		Completion event for nand status events.
> > + * @status:		Status of the flash device.
> > + * @prog:		Used to initiate controller operations.
> > + */
> > +struct anfc_nand_controller {
> > +	struct nand_controller controller;
> > +	struct list_head chips;
> > +	struct device *dev;
> > +	void __iomem *base;
> > +	struct clk *clk_sys;
> > +	struct clk *clk_flash;
> > +	int irq;
> > +	int csnum;
> > +	struct completion event;
> > +	int status;
> > +	u8 buf[TEMP_BUF_SIZE];
> 
> Allocate this buf dynamically.
Ok
> 
> > +	u32 eccval;
> > +};
> 
> > +static int anfc_page_write_type_exec(struct nand_chip *chip,
> > +				     const struct nand_subop *subop) {
> > +	const struct nand_op_instr *instr;
> > +	struct anfc_nand_chip *achip = to_anfc_nand(chip);
> > +	struct anfc_nand_controller *nfc = to_anfc(chip->controller);
> > +	unsigned int op_id, len;
> > +	struct anfc_op nfc_op = {};
> > +	struct mtd_info *mtd = nand_to_mtd(chip);
> > +
> > +	anfc_parse_instructions(chip, subop, &nfc_op);
> > +	instr = nfc_op.data_instr;
> > +	op_id = nfc_op.data_instr_idx;
> > +	anfc_prepare_cmd(chip, nfc_op.cmds[0], nfc_op.cmds[1], 1,
> > +			 mtd->writesize, nfc_op.naddrcycles);
> > +	anfc_setpagecoladdr(nfc, nfc_op.row, nfc_op.col);
> > +	if (!nfc_op.data_instr)
> > +		return 0;
> > +
> > +	len = nand_subop_get_data_len(subop, op_id);
> > +	anfc_write_data_op(chip,  (char *)instr->ctx.data.buf.out,
> 
> 				^ extra white space here
> and please drop the cast.
Ok
> 
> Can you please run checkpatch --strict prior to submitting patches?
I ran it with --strict while submitting the patch, but I didn't find any warning.
Anyway I will correct it.
> 
> > +			   mtd->writesize,
> > +			   DIV_ROUND_UP(mtd->writesize, achip->pktsize),
> 
> No, that's wrong. You should use instr->ctx.data.len here, and the
> DIV_ROUND_UP() thing is a bit scary. That means you might be writing more data than
> requested.
Ok. Got it.
> 
> > +			   achip->pktsize);
> > +
> > +	return 0;
> > +}
> > +
> 
> > +
> > +static int anfc_probe(struct platform_device *pdev) {
> > +	struct anfc_nand_controller *nfc;
> > +	struct anfc_nand_chip *anand_chip;
> > +	struct device_node *np = pdev->dev.of_node, *child;
> > +	struct resource *res;
> > +	int err;
> > +
> > +	nfc = devm_kzalloc(&pdev->dev, sizeof(*nfc), GFP_KERNEL);
> > +	if (!nfc)
> > +		return -ENOMEM;
> > +
> > +	nand_controller_init(&nfc->controller);
> > +	INIT_LIST_HEAD(&nfc->chips);
> > +	init_completion(&nfc->event);
> > +	nfc->dev = &pdev->dev;
> > +	platform_set_drvdata(pdev, nfc);
> > +	nfc->csnum = -1;
> > +	nfc->controller.ops = &anfc_nand_controller_ops;
> 
> Add a blank line here please
Ok, I will update
> 
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	nfc->base = devm_ioremap_resource(&pdev->dev, res);
> > +	if (IS_ERR(nfc->base))
> > +		return PTR_ERR(nfc->base);
> 
> and here
Ok, I will update
> 
> > +	nfc->irq = platform_get_irq(pdev, 0);
> > +	if (nfc->irq < 0) {
> > +		dev_err(&pdev->dev, "platform_get_irq failed\n");
> > +		return -ENXIO;
> > +	}
> 
> and here
Ok, I will update
> 
> > +	dma_set_mask(&pdev->dev, DMA_BIT_MASK(64));
> 
> Is this really needed?
Yes, As our DMA supports 64bit addressing. It is needed
> 
> > +	err = devm_request_irq(&pdev->dev, nfc->irq, anfc_irq_handler,
> > +			       0, "arasannfc", nfc);
> > +	if (err)
> > +		return err;
> 
> Add a blank line here too.
Ok, I will update
> 
> > +	nfc->clk_sys = devm_clk_get(&pdev->dev, "clk_sys");
> > +	if (IS_ERR(nfc->clk_sys)) {
> > +		dev_err(&pdev->dev, "sys clock not found.\n");
> > +		return PTR_ERR(nfc->clk_sys);
> > +	}
> > +
> > +	nfc->clk_flash = devm_clk_get(&pdev->dev, "clk_flash");
> > +	if (IS_ERR(nfc->clk_flash)) {
> > +		dev_err(&pdev->dev, "flash clock not found.\n");
> > +		return PTR_ERR(nfc->clk_flash);
> > +	}
> > +
> > +	err = clk_prepare_enable(nfc->clk_sys);
> > +	if (err) {
> > +		dev_err(&pdev->dev, "Unable to enable sys clock.\n");
> > +		return err;
> > +	}
> > +
> > +	err = clk_prepare_enable(nfc->clk_flash);
> > +	if (err) {
> > +		dev_err(&pdev->dev, "Unable to enable flash clock.\n");
> > +		goto clk_dis_sys;
> > +	}
> > +
> > +	for_each_available_child_of_node(np, child) {
> > +		anand_chip = devm_kzalloc(&pdev->dev, sizeof(*anand_chip),
> > +					  GFP_KERNEL);
> > +		if (!anand_chip) {
> > +			of_node_put(child);
> > +			err = -ENOMEM;
> > +			goto nandchip_clean_up;
> > +		}
> 
> and here.
Ok, I will update
> 
> > +		err = anfc_nand_chip_init(nfc, anand_chip, child);
> > +		if (err) {
> > +			devm_kfree(&pdev->dev, anand_chip);
> 
> We usually try to avoid calling devm_kfree(). I guess you do it to avoid keeping the chip obj
> around when init failed, but this should be rare enough so we can actually ignore it and let the
> mem allocated for the NFC lifetime.
Ok. I understood.
> 
> > +			continue;
> > +		}
> > +
> > +		list_add_tail(&anand_chip->node, &nfc->chips);
> > +	}
> > +	return 0;
> > +
> > +nandchip_clean_up:
> > +	list_for_each_entry(anand_chip, &nfc->chips, node)
> > +		nand_release(&anand_chip->chip);
> 
> Blank line here.
Ok, I will update
> 
> > +	clk_disable_unprepare(nfc->clk_flash);
> 
> Blank line here.
Ok, I will update
> 
> > +clk_dis_sys:
> > +	clk_disable_unprepare(nfc->clk_sys);
> > +
> > +	return err;
> > +}
> 
> Regards,
> 
> Boris

Boris/Miquel, could you please review the remaining code as well, if you feel
There is still something to improve.
One concern I have is especially anfc_read_page_hwecc(), there I am checking erased pages bit flips.
Since Arasan NAND controller doesn't have multibit error detection beyond 24-bit( it can correct upto 24 bit errors), 
I took some error count as default value(16, I put this based on the error count that I got while reading erased page on Micron device).
I will just read the error count register and compare this value with the default error count(16) and if it is more
Than default then I am checking for erased page bit flips.
I am doubting that this will not work in all cases.
In my case it is just working because the error count that it got on an erased page is 16.
Could you please suggest a way to do detect erased_page bit flips.

Thanks,
Naga Sureshkumar Relli

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