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Date:   Sun, 10 Jan 2021 09:19:44 +0530
From:   mdalam@...eaurora.org
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     miquel.raynal@...tlin.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, boris.brezillon@...labora.com,
        sricharan@...eaurora.org
Subject: Re: [PATCH] mtd: rawnand: qcom: update last code word register

On 2021-01-05 21:15, Manivannan Sadhasivam wrote:
> On Tue, Jan 05, 2021 at 12:24:45AM +0530, mdalam@...eaurora.org wrote:
>> On 2020-12-31 16:23, Manivannan Sadhasivam wrote:
>> > On Thu, Dec 17, 2020 at 07:32:56PM +0530, Md Sadre Alam wrote:
>> > > From QPIC version 2.0 onwards new register got added to
>> > > read last codeword. This change will update the same.
>> > >
>> > > For first three code word READ_LOCATION_n register will be
>> > > use.For last code wrod READ_LOCATION_LAST_CW_n register will be
>> > > use.
>> > >
>> > > Signed-off-by: Md Sadre Alam <mdalam@...eaurora.org>
>> > > ---
>> > >  drivers/mtd/nand/raw/qcom_nandc.c | 79
>> > > +++++++++++++++++++++++++++++++++------
>> > >  1 file changed, 67 insertions(+), 12 deletions(-)
>> > >
>> > > diff --git a/drivers/mtd/nand/raw/qcom_nandc.c
>> > > b/drivers/mtd/nand/raw/qcom_nandc.c
>> > > index 667e4bf..eaef51d 100644
>> > > --- a/drivers/mtd/nand/raw/qcom_nandc.c
>> > > +++ b/drivers/mtd/nand/raw/qcom_nandc.c
>> > > @@ -48,6 +48,10 @@
>> > >  #define	NAND_READ_LOCATION_1		0xf24
>> > >  #define	NAND_READ_LOCATION_2		0xf28
>> > >  #define	NAND_READ_LOCATION_3		0xf2c
>> > > +#define NAND_READ_LOCATION_LAST_CW_0    0xf40
>> > > +#define NAND_READ_LOCATION_LAST_CW_1    0xf44
>> > > +#define NAND_READ_LOCATION_LAST_CW_2    0xf48
>> > > +#define NAND_READ_LOCATION_LAST_CW_3    0xf4c
>> >
>> > Please keep the alignment as before.
>> >
>>  Fixed alignment in V2 patch
>> > >
>> > >  /* dummy register offsets, used by write_reg_dma */
>> > >  #define	NAND_DEV_CMD1_RESTORE		0xdead
>> > > @@ -187,6 +191,12 @@ nandc_set_reg(nandc,
>> > > NAND_READ_LOCATION_##reg,			\
>> > >  	      ((size) << READ_LOCATION_SIZE) |			\
>> > >  	      ((is_last) << READ_LOCATION_LAST))
>> > >
>> > > +#define nandc_set_read_loc_last(nandc, reg, offset, size, is_last)	\
>> > > +nandc_set_reg(nandc, NAND_READ_LOCATION_LAST_CW_##reg,			\
>> > > +	      ((offset) << READ_LOCATION_OFFSET) |		\
>> > > +	      ((size) << READ_LOCATION_SIZE) |			\
>> > > +	      ((is_last) << READ_LOCATION_LAST))
>> > > +
>> > >  /*
>> > >   * Returns the actual register address for all NAND_DEV_ registers
>> > >   * (i.e. NAND_DEV_CMD0, NAND_DEV_CMD1, NAND_DEV_CMD2 and
>> > > NAND_DEV_CMD_VLD)
>> > > @@ -316,6 +326,10 @@ struct nandc_regs {
>> > >  	__le32 read_location1;
>> > >  	__le32 read_location2;
>> > >  	__le32 read_location3;
>> > > +	__le32 read_location_last0;
>> > > +	__le32 read_location_last1;
>> > > +	__le32 read_location_last2;
>> > > +	__le32 read_location_last3;
>> > >
>> > >  	__le32 erased_cw_detect_cfg_clr;
>> > >  	__le32 erased_cw_detect_cfg_set;
>> > > @@ -644,6 +658,14 @@ static __le32 *offset_to_nandc_reg(struct
>> > > nandc_regs *regs, int offset)
>> > >  		return &regs->read_location2;
>> > >  	case NAND_READ_LOCATION_3:
>> > >  		return &regs->read_location3;
>> > > +	case NAND_READ_LOCATION_LAST_CW_0:
>> > > +		return &regs->read_location_last0;
>> > > +	case NAND_READ_LOCATION_LAST_CW_1:
>> > > +		return &regs->read_location_last1;
>> > > +	case NAND_READ_LOCATION_LAST_CW_2:
>> > > +		return &regs->read_location_last2;
>> > > +	case NAND_READ_LOCATION_LAST_CW_3:
>> > > +		return &regs->read_location_last3;
>> > >  	default:
>> > >  		return NULL;
>> > >  	}
>> > > @@ -719,9 +741,13 @@ static void update_rw_regs(struct
>> > > qcom_nand_host *host, int num_cw, bool read)
>> > >  	nandc_set_reg(nandc, NAND_READ_STATUS, host->clrreadstatus);
>> > >  	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);
>> > >
>> > > -	if (read)
>> > > +	if (read) {
>> > > +		if (nandc->props->qpic_v2)
>> > > +			nandc_set_read_loc_last(nandc, 0, 0, host->use_ecc ?
>> > > +					host->cw_data : host->cw_size, 1);
>> >
>> > Forgot to add else? Otherwise both NAND_READ_LOCATION_n and
>> > NAND_READ_LOCATION_LAST_CW_n
>> > will be used.
>> 
>>   Here else is not needed , because to read last code word we need to
>> configure
>>   NAND_READ_LOCATION_LAST_CW_n register. Any way here we are doing 
>> only
>> register configuration.
>>   for all the code words. Earlier version of QPIC we were using
>> nandc_set_read_loc()
>>   for all the code words, but in qpic V2 onwards for last code word we 
>> have
>> to use
>>   NAND_READ_LOCATION_LAST_CW_n register. So configuring here the same.
>> 
> 
> nandc_set_read_loc() has the last argument "is_last". This is used to 
> convey
> whether we need to set READ_LOCATION_LAST bit or not. This is fine for 
> QPIC
> IP < 2, but for >=2 we need to use nandc_set_read_loc_last() only. My 
> point
> is why do you need to still use nandc_set_read_loc() here for QPIC v2? 
> That's
> why I asked you about using else().
> 
   Got it. I fixed this in V3 patch.
>> 
>> >
>> > >  		nandc_set_read_loc(nandc, 0, 0, host->use_ecc ?
>> > >  				   host->cw_data : host->cw_size, 1);
>> > > +	}
>> > >  }
>> > >
>> > >  /*
>> > > @@ -1096,9 +1122,13 @@ static void config_nand_page_read(struct
>> > > qcom_nand_controller *nandc)
>> > >  static void
>> > >  config_nand_cw_read(struct qcom_nand_controller *nandc, bool use_ecc)
>> > >  {
>> > > -	if (nandc->props->is_bam)
>> > > +	if (nandc->props->is_bam) {
>> > > +		if (nandc->props->qpic_v2)
>> > > +			write_reg_dma(nandc, NAND_READ_LOCATION_LAST_CW_0,
>> > > +				      4, NAND_BAM_NEXT_SGL);
>> > >  		write_reg_dma(nandc, NAND_READ_LOCATION_0, 4,
>> > >  			      NAND_BAM_NEXT_SGL);
>> >
>> > Don't you need to modify the number of registers to write? It can't be 4
>> > all the
>> > time if NAND_READ_LOCATION_LAST_CW_0 is used.
>> 
>>   Changed number of registers to write from 4 to 1 in V2 patch for 
>> register
>> NAND_READ_LOCATION_LAST_CW_0 .
>> >
>> > > +	}
>> > >
>> > >  	write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
>> > >  	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);
>> > > @@ -1633,16 +1663,28 @@ qcom_nandc_read_cw_raw(struct mtd_info *mtd,
>> > > struct nand_chip *chip,
>> > >  	}
>> > >
>> > >  	if (nandc->props->is_bam) {
>> > > -		nandc_set_read_loc(nandc, 0, read_loc, data_size1, 0);
>> > > +		if (nandc->props->qpic_v2 && cw == (ecc->steps - 1))
>> > > +			nandc_set_read_loc_last(nandc, 0, read_loc, data_size1, 0);
>> > > +		else
>> > > +			nandc_set_read_loc(nandc, 0, read_loc, data_size1, 0);
>> >
>> > IIUC nandc_set_read_loc_last() is only needed to read the last codeword
>> > which is
>> > handled by the last command in this function:
>> 
>>   Function qcom_nandc_read_cw_raw() is getting called for each code 
>> word for
>> raw read and its reading
>>   one code word at a time. So to read last code word when condition cw 
>> ==
>> (ecc->steps - 1) will match, we have
>>   to configure NAND_READ_LOCATION_LAST_CW_n register. Because below 
>> piece of
>> code is doing one code word
>>   read for first three code word so same logic will also apply for 
>> last code
>> word as well.
>> 
> 
> Fine, but still "cw == (ecc->steps - 1)" will stay same for all 
> comparisions
> in this function, right? So why can't you use it only for the last 
> command?
> 
    Yes I understand, but data_size1, oob_size1, data_size2 and oob_size2 
are the sizes
    to extract these many bytes of data from buff whose offset specified 
by the register
    QPIC_NAND_READ_LOCATION_LAST_CW_n. "read_loc" also changing. 
"is_last" is just a flag
    which indicate this is the last read location to process.For last 
code word also we  are
    updating data_size1, oob_size1, data_size2 and oob_size2 so condition 
should be applied for
    all command not only for last command.
>> >
>> > nandc_set_read_loc(nandc, 3, read_loc, oob_size2, 1);
>> >
>> > >  		read_loc += data_size1;
>> > >
>> > > -		nandc_set_read_loc(nandc, 1, read_loc, oob_size1, 0);
>> > > +		if (nandc->props->qpic_v2 && cw == (ecc->steps - 1))
>> > > +			nandc_set_read_loc_last(nandc, 1, read_loc, oob_size1, 0);
>> > > +		else
>> > > +			nandc_set_read_loc(nandc, 1, read_loc, oob_size1, 0);
>> > >  		read_loc += oob_size1;
>> > >
>> > > -		nandc_set_read_loc(nandc, 2, read_loc, data_size2, 0);
>> > > +		if (nandc->props->qpic_v2 && cw == (ecc->steps - 1))
>> > > +			nandc_set_read_loc_last(nandc, 2, read_loc, data_size2, 0);
>> > > +		else
>> > > +			nandc_set_read_loc(nandc, 2, read_loc, data_size2, 0);
>> > >  		read_loc += data_size2;
>> > >
>> > > -		nandc_set_read_loc(nandc, 3, read_loc, oob_size2, 1);
>> > > +		if (nandc->props->qpic_v2 && cw == (ecc->steps - 1))
>> > > +			nandc_set_read_loc_last(nandc, 3, read_loc, oob_size2, 0);
>> > > +		else
>> > > +			nandc_set_read_loc(nandc, 3, read_loc, oob_size2, 1);
>> > >  	}
>> > >
>> > >  	config_nand_cw_read(nandc, false);
>> > > @@ -1873,14 +1915,27 @@ static int read_page_ecc(struct
>> > > qcom_nand_host *host, u8 *data_buf,
>> > >
>> > >  		if (nandc->props->is_bam) {
>> > >  			if (data_buf && oob_buf) {
>> > > -				nandc_set_read_loc(nandc, 0, 0, data_size, 0);
>> > > -				nandc_set_read_loc(nandc, 1, data_size,
>> > > -						   oob_size, 1);
>> > > +				if (nandc->props->qpic_v2 && i == (ecc->steps - 1)) {
>> > > +					nandc_set_read_loc_last(nandc, 0, 0, data_size, 0);
>> >
>> > Why do you need this? Can't you use nandc_set_read_loc()? Same for below
>> > cases.
>> 
>>   Here we are looping for all the code words and when we will do
>> configuration for last
>>   code word we have to use NAND_READ_LOCATION_LAST_CW_n register 
>> that's why
>> i am using
>>   nandc_set_read_loc_last() instead of nandc_set_read_loc().
>> >
> 
> Sorry, confused! You are calling nandc_set_read_loc_last() twice and 
> only the
> last one has "is_last" flag set. Can you please clarify?

   For last code word , in first call of nandc_set_read_loc_last() 
"data_size" bytes will get extracted.
   and in the the second call of nandc_set_read_loc_last() "oob_size" 
bytes will get extracted and this
   is the last read location to process so I am setting "is_last" flag in 
the second call.
> 
> Thanks,
> Mani
> 
>> > Thanks,
>> > Mani
>> >
>> > > +					nandc_set_read_loc_last(nandc, 1, data_size,
>> > > +								oob_size, 1);
>> > > +				} else {
>> > > +					nandc_set_read_loc(nandc, 0, 0, data_size, 0);
>> > > +					nandc_set_read_loc(nandc, 1, data_size,
>> > > +							   oob_size, 1);
>> > > +				}
>> > >  			} else if (data_buf) {
>> > > -				nandc_set_read_loc(nandc, 0, 0, data_size, 1);
>> > > +				if (nandc->props->qpic_v2 && i == (ecc->steps - 1))
>> > > +					nandc_set_read_loc_last(nandc, 0, 0, data_size, 1);
>> > > +				else
>> > > +					nandc_set_read_loc(nandc, 0, 0, data_size, 1);
>> > >  			} else {
>> > > -				nandc_set_read_loc(nandc, 0, data_size,
>> > > -						   oob_size, 1);
>> > > +				if (nandc->props->qpic_v2 && i == (ecc->steps - 1))
>> > > +					nandc_set_read_loc_last(nandc, 0, data_size,
>> > > +								oob_size, 1);
>> > > +				else
>> > > +					nandc_set_read_loc(nandc, 0, data_size,
>> > > +							   oob_size, 1);
>> > >  			}
>> > >  		}
>> > >
>> > > --
>> > > 2.7.4
>> > >

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