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Date:   Wed, 24 Feb 2021 01:13:42 +0530
From:   mdalam@codeaurora.org
To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     mani@kernel.org, boris.brezillon@collabora.com,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        sricharan@codeaurora.org
Subject: Re: [PATCH] mtd: rawnand: qcom: update last code word register
In-Reply-To: <20210223173449.1a55df1e@xps13>
References: <1614024267-12529-1-git-send-email-mdalam@codeaurora.org>
 <20210223173449.1a55df1e@xps13>
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On 2021-02-23 22:04, Miquel Raynal wrote:
> Hello,
> 
> Md Sadre Alam <mdalam@codeaurora.org> wrote on Tue, 23 Feb 2021
> 01:34:27 +0530:
> 
>> From QPIC version 2.0 onwards new register got added to read last
> 
>                                a new
> 
>> codeword. This change will add the READ_LOCATION_LAST_CW_n register.
> 
>             Add support for this READ_LOCATION_LAST_CW_n register.
> 
>> 
>> For first three code word READ_LOCATION_n register will be
>> use.For last code word READ_LOCATION_LAST_CW_n register will be
>> use.
> 
> "
> In the case of QPIC v2, codewords 0, 1 and 2 will be accessed through
> READ_LOCATION_n, while codeword 3 will be accessed through
> READ_LOCATION_LAST_CW_n.
> "
> 
> When I read my own sentence, I feel that there is something wrong.
> If there are only 4 codewords, I guess a QPIC v2 is able to use
> READ_LOCATION_3 or READ_LOCATION_LAST_CW_0 interchangeably. Isn't it?
> 
> I guess the point of having these "last_cw_n" registers is to support
> up to 8 codewords, am I wrong? If this the case, the current patch
> completely fails doing that I don't get the point of such change.

This register is only use to read last code word.

I have address all the comments from all the previous sub sequent 
patches and pushed
all patches in only one series.

Please check.

> 
>> Signed-off-by: Md Sadre Alam <mdalam@codeaurora.org>
>> ---
> 
> [...]
> 
>>  /* helper to configure address register values */
>> @@ -700,8 +727,9 @@ static void set_address(struct qcom_nand_host 
>> *host, u16 column, int page)
>>   *
>>   * @num_cw:		number of steps for the read/write operation
>>   * @read:		read or write operation
>> + * @cw	:		which code word
>>   */
>> -static void update_rw_regs(struct qcom_nand_host *host, int num_cw, 
>> bool read)
>> +static void update_rw_regs(struct qcom_nand_host *host, int num_cw, 
>> bool read, int cw)
>>  {
>>  	struct nand_chip *chip = &host->chip;
>>  	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
>> @@ -740,7 +768,7 @@ static void update_rw_regs(struct qcom_nand_host 
>> *host, int num_cw, bool read)
>>  	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);
>> 
>>  	if (read)
>> -		nandc_set_read_loc(chip, 0, 0, 0, host->use_ecc ?
>> +		nandc_set_read_loc(chip, cw, 0, 0, host->use_ecc ?
>>  				   host->cw_data : host->cw_size, 1);
>>  }
>> 
>> @@ -1111,18 +1139,34 @@ static void config_nand_page_read(struct 
>> nand_chip *chip)
>>  		      NAND_ERASED_CW_SET | NAND_BAM_NEXT_SGL);
>>  }
>> 
>> +/* helper to check which location register should be use for this
> 
>     /*
>      * Check which location...
> 
>> + * code word. NAND_READ_LOCATION or NAND_READ_LOCATION_LAST_CW
>> + */
>> +static bool config_loc_last_reg(struct nand_chip *chip, int cw)
>> +{
>> +	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
>> +	struct nand_ecc_ctrl *ecc = &chip->ecc;
>> +
>> +	if (nandc->props->qpic_v2 && qcom_nandc_is_last_cw(ecc, cw))
>> +		return true;
> 
> Not sure this is really useful, it's probably better to drop this
> helper and just use...
> 
>> +
>> +	return false;
>> +}
>>  /*
>>   * Helper to prepare DMA descriptors for configuring registers
>>   * before reading each codeword in NAND page.
>>   */
>>  static void
>> -config_nand_cw_read(struct nand_chip *chip, bool use_ecc)
>> +config_nand_cw_read(struct nand_chip *chip, bool use_ecc, int cw)
>>  {
>>  	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
>> +	int reg = NAND_READ_LOCATION_0;
>> +
>> +	if (config_loc_last_reg(chip, cw))
> 
> ...     if (nandc->props->qpic_v2 && qcom_nandc_is_lastcw()) here.
> 
>> +		reg = NAND_READ_LOCATION_LAST_CW_0;
>> 
>>  	if (nandc->props->is_bam)
>> -		write_reg_dma(nandc, NAND_READ_LOCATION_0, 4,
>> -			      NAND_BAM_NEXT_SGL);
>> +		write_reg_dma(nandc, reg, 4, NAND_BAM_NEXT_SGL);
>> 
>>  	write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
>>  	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);
>> @@ -1142,12 +1186,12 @@ config_nand_cw_read(struct nand_chip *chip, 
>> bool use_ecc)
> 
> Thanks,
> Miquèl