linux-kernel - Re: [PATCH V4] mtd: rawnand: qcom: update last code word register

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Message-ID: <bd4f0fea5d074c98dc3ce3b2113d30ee@codeaurora.org>
Date:   Mon, 15 Feb 2021 02:50:41 +0530
From:   mdalam@...eaurora.org
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        boris.brezillon@...labora.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, vigneshr@...com,
        sricharan@...eaurora.org
Subject: Re: [PATCH V4] mtd: rawnand: qcom: update last code word register

On 2021-02-12 13:49, Miquel Raynal wrote:
> Hello,
> 
> mdalam@...eaurora.org wrote on Fri, 12 Feb 2021 01:00:47 +0530:
> 
>> On 2021-02-11 19:37, Miquel Raynal wrote:
>> > Hello,
>> >
>> > Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote on Wed,
>> > 10 Feb 2021 14:31:44 +0530:
>> >
>> >> On Fri, Jan 29, 2021 at 03:09:19AM +0530, Md Sadre Alam wrote:
>> >> > From QPIC version 2.0 onwards new register got added to
>> >> > read last codeword. This change will add the 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.
>> >
>> > Sorry for the late notice, I think the patch is fine but if you don't
>> > mind I would like to propose a small change that should simplify your
>> > patch a lot, see below.
>> >
>> >> >
>> >> > Signed-off-by: Md Sadre Alam <mdalam@...eaurora.org>
>> >> >> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>> >> >> Thanks,
>> >> Mani
>> >> >> > ---
>> >> > [V4]
>> >> >  * Modified condition for nandc_set_read_loc_last() in qcom_nandc_read_cw_raw().
>> >> >  * Added one additional argument "last_cw" to the function config_nand_cw_read()
>> >> >    to handle last code word condition.
>> >> >  * Changed total number of last code word register "NAND_READ_LOCATION_LAST_CW_0" to 4
>> >> >    while doing code word configuration.
>> >> >  drivers/mtd/nand/raw/qcom_nandc.c | 110 +++++++++++++++++++++++++++++---------
>> >> >  1 file changed, 84 insertions(+), 26 deletions(-)
>> >> >
>> >> > diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
>> >> > index 667e4bf..9484be8 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
>> >> >
>> >> >  /* 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))
>> >> > +
>> >
>> > You could rename the macro nandc_set_read_loc() into
>> > nandc_set_read_loc_first() or anything else that make sense, then have
>> > a helper which does:
>> >
>> > nandc_set_read_loc()
>> > {
>> > 	if (condition for first)
>> > 		return nandc_set_read_loc_first();
>> > 	else
>> > 		return nandc_set_read_loc_last();
>> > }
>> >
>> 
>>    Yes this is more precise way & simplify the patch a lot.
>>    But for this i have to change these two macro as a function.
>> 
>>    nandc_set_read_loc() & nandc_set_read_loc_last().
>> 
>>    Since for last code word register we are using Token Pasting 
>> Operator##.
>> 
>>    So if i am implementing like the below.
>> 
>>    /* helper to configure location register values */
>>    static void nandc_set_read_loc(struct qcom_nand_controller *nandc, 
>> int reg,
>>                    int offset, int size, int is_last, bool last_cw)
>>    {
>>            if (last_cw)
>>                    return nandc_set_read_loc_last(nandc, reg, offset, 
>> size, is_last);
>>            else
>>                    return nandc_set_read_loc_first(nandc, reg, offset, 
>> size, is_last);
>>   }
>> 
>>    So here for macro expansion reg should be a value not a variable 
>> else it will be expended like
>>    NAND_READ_LOCATION_LAST_CW_reg instead of 
>> NAND_READ_LOCATION_LAST_CW_0,1,2,3 etc.
> 
> I know it involves a little bit more computation but I wonder if using
> funcs instead of macros here would not be nicer? Perhaps something 
> like:
> 
> 	loc = is_last ? NAND_READ_LOCATION /* 0xf20 */ :
> NAND_READ_LOCATION_LAST /* 0xf40 */;
> 	loc += reg * 2;

   I have added a helper function to update location register value in V5 
patch.
   Please check the patch.
> 
>>   the call for nandc_set_read_loc() as nandc_set_read_loc(nandc, 0, 
>> read_loc, data_size1, 0, true); ---> for last code word.
>>   nandc_set_read_loc(nandc, 0, read_loc, data_size1, 0, false); ---> 
>> for first three code wrod.
> 
> I think it's best to forward 'cw' as a parameter and do the
> computation of is_last locally.
> 
>>   So is this ok for you to convert these two macro into function ?
>> 
>> > And in the rest of your patch you won't have to touch anything else.
>> >
>> > Thanks,
>> > Miquèl
> 
> Thanks,
> Miquèl