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Date:   Tue, 25 Jun 2019 14:02:33 +0100
From:   Piotr Sroka <piotrs@cadence.com>
To:     Dmitry Osipenko <digetx@gmail.com>
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Subject: Re: [v3 1/2] mtd: nand: Add Cadence NAND controller driver
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Hi Dmitry

The 06/16/2019 16:42, Dmitry Osipenko wrote:
>EXTERNAL MAIL
>
>
>14.06.2019 18:09, Piotr Sroka пишет:
>
>Commit description is mandatory.
>
>> Signed-off-by: Piotr Sroka <piotrs@cadence.com>
>> ---
>
>[snip]
>
>> +
>> +/* Cadnence NAND flash controller capabilities get from driver data. */
>> +struct cadence_nand_dt_devdata {
>> +	/* Skew value of the output signals of the NAND Flash interface. */
>> +	u32 if_skew;
>> +	/* It informs if aging feature in the DLL PHY supported. */
>> +	u8 phy_dll_aging;
>> +	/*
>> +	 * It informs if per bit deskew for read and write path in
>> +	 * the PHY is supported.
>> +	 */
>> +	u8 phy_per_bit_deskew;
>> +	/* It informs if slave DMA interface is connected to DMA engine. */
>> +	u8 has_dma;
>
>There is no needed to dedicate 8 bits to a variable if you only care about a single
>bit. You may write this as:
>
>bool has_dma : 1;
I modified it locally but it looks that checkpatch does not like such
notation
"WARNING: Avoid using bool as bitfield.  Prefer bool bitfields as
unsigned int or u<8|16|32>"
So maybe I will leave it as is.

>[snip]
>
>> +static struct
>> +cdns_nand_chip *to_cdns_nand_chip(struct nand_chip *chip)
>> +{
>> +	return container_of(chip, struct cdns_nand_chip, chip);
>> +}
>> +
>> +static struct
>> +cdns_nand_ctrl *to_cdns_nand_ctrl(struct nand_controller *controller)
>> +{
>> +	return container_of(controller, struct cdns_nand_ctrl, controller);
>> +}
>
>It's better to inline explicitly such cases because they won't get inlined with some
>kernel configurations, like enabled ftracing for example.
>
>> +static bool
>> +cadence_nand_dma_buf_ok(struct cdns_nand_ctrl *cdns_ctrl, const void *buf,
>> +			u32 buf_len)
>> +{
>> +	u8 data_dma_width = cdns_ctrl->caps2.data_dma_width;
>> +
>> +	return buf && virt_addr_valid(buf) &&
>> +		likely(IS_ALIGNED((uintptr_t)buf, data_dma_width)) &&
>> +		likely(IS_ALIGNED(buf_len, data_dma_width));
>> +}
>> +
>> +static int cadence_nand_wait_for_value(struct cdns_nand_ctrl *cdns_ctrl,
>> +				       u32 reg_offset, u32 timeout_us,
>> +				       u32 mask, bool is_clear)
>> +{
>> +	u32 val;
>> +	int ret = 0;
>> +
>> +	ret = readl_poll_timeout(cdns_ctrl->reg + reg_offset,
>> +				 val, !(val & mask) == is_clear,
>> +				 10, timeout_us);
>
>Apparently you don't care about having memory barrier here, hence
>readl_relaxed_poll_timeout().
ok I will update it.
>
>> +	if (ret < 0) {
>> +		dev_err(cdns_ctrl->dev,
>> +			"Timeout while waiting for reg %x with mask %x is clear %d\n",
>> +			reg_offset, mask, is_clear);
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +static int cadence_nand_set_ecc_enable(struct cdns_nand_ctrl *cdns_ctrl,
>> +				       bool enable)
>> +{
>> +	u32 reg;
>> +
>> +	if (cadence_nand_wait_for_value(cdns_ctrl, CTRL_STATUS,
>> +					1000000,
>> +					CTRL_STATUS_CTRL_BUSY, true))
>> +		return -ETIMEDOUT;
>> +
>> +	reg = readl(cdns_ctrl->reg + ECC_CONFIG_0);
>> +
>> +	if (enable)
>> +		reg |= ECC_CONFIG_0_ECC_EN;
>> +	else
>> +		reg &= ~ECC_CONFIG_0_ECC_EN;
>> +
>> +	writel(reg, cdns_ctrl->reg + ECC_CONFIG_0);
>
>And here.. looks like there is no need for the memory barries, hence use the relaxed
>versions of readl/writel. Same for the rest of the patch.
>
ok
>> +	return 0;
>> +}
>> +
>> +static void cadence_nand_set_ecc_strength(struct cdns_nand_ctrl *cdns_ctrl,
>> +					  u8 corr_str_idx)
>> +{
>> +	u32 reg;
>> +
>> +	if (cdns_ctrl->curr_corr_str_idx == corr_str_idx)
>> +		return;
>> +
>> +	reg = readl(cdns_ctrl->reg + ECC_CONFIG_0);
>> +	reg &= ~ECC_CONFIG_0_CORR_STR;
>> +	reg |= FIELD_PREP(ECC_CONFIG_0_CORR_STR, corr_str_idx);
>> +	writel(reg, cdns_ctrl->reg + ECC_CONFIG_0);
>> +
>> +	cdns_ctrl->curr_corr_str_idx = corr_str_idx;
>> +}
>> +
>> +static u8 cadence_nand_get_ecc_strength_idx(struct cdns_nand_ctrl *cdns_ctrl,
>> +					    u8 strength)
>> +{
>> +	u8 i, corr_str_idx = 0;
>> +
>> +	for (i = 0; i < BCH_MAX_NUM_CORR_CAPS; i++) {
>> +		if (cdns_ctrl->ecc_strengths[i] == strength) {
>> +			corr_str_idx = i;
>> +			break;
>> +		}
>> +	}
>
>Is it a error case when i == BCH_MAX_NUM_CORR_CAPS?
Yes it is an error but it could appear only if ECC capability registers
have wrong values. I will handle that error anyway.

>> +	return corr_str_idx;
>> +}
>> +
>> +static int cadence_nand_set_skip_marker_val(struct cdns_nand_ctrl *cdns_ctrl,
>> +					    u16 marker_value)
>> +{
>> +	u32 reg = 0;
>> +
>> +	if (cadence_nand_wait_for_value(cdns_ctrl, CTRL_STATUS,
>> +					1000000,
>> +					CTRL_STATUS_CTRL_BUSY, true))
>> +		return -ETIMEDOUT;
>> +
>> +	reg = readl(cdns_ctrl->reg + SKIP_BYTES_CONF);
>> +	reg &= ~SKIP_BYTES_MARKER_VALUE;
>> +	reg |= FIELD_PREP(SKIP_BYTES_MARKER_VALUE,
>> +		    marker_value);
>> +
>> +	writel(reg, cdns_ctrl->reg + SKIP_BYTES_CONF);
>> +
>> +	return 0;
>> +}
>> +
>> +static int cadence_nand_set_skip_bytes_conf(struct cdns_nand_ctrl *cdns_ctrl,
>> +					    u8 num_of_bytes,
>> +					    u32 offset_value,
>> +					    int enable)
>> +{
>> +	u32 reg = 0;
>> +	u32 skip_bytes_offset = 0;
>
>Please don't initialize variables if not necessary. You could also write this in a
>single line.
>
>	u32 skip_bytes_offset, reg;
>
>Same for the rest of the patch.
>
Ok to I will change it.
>> +	if (cadence_nand_wait_for_value(cdns_ctrl, CTRL_STATUS,
>> +					1000000,
>> +					CTRL_STATUS_CTRL_BUSY, true))
>> +		return -ETIMEDOUT;
>> +
>> +	if (!enable) {
>> +		num_of_bytes = 0;
>> +		offset_value = 0;
>> +	}
>> +
>> +	reg = readl(cdns_ctrl->reg + SKIP_BYTES_CONF);
>> +	reg &= ~SKIP_BYTES_NUM_OF_BYTES;
>> +	reg |= FIELD_PREP(SKIP_BYTES_NUM_OF_BYTES,
>> +		    num_of_bytes);
>> +	skip_bytes_offset = FIELD_PREP(SKIP_BYTES_OFFSET_VALUE,
>> +				       offset_value);
>> +
>> +	writel(reg, cdns_ctrl->reg + SKIP_BYTES_CONF);
>> +	writel(skip_bytes_offset, cdns_ctrl->reg + SKIP_BYTES_OFFSET);
>> +
>> +	return 0;
>> +}
>> +
>> +/* Fucntions enables/disables hardware detection of erased data */
>
>s/Fucntions/Function/, please use spellchecker. I'd also recommend to start all
>single-line comments with a lower case (and without a dot in the end) because it is a
>more common style in the kernel and is a bit easier for the eyes.
Ok  I will do it. 
>
>[snip]
  
Thanks
Piotr Sroka