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Date:   Fri, 12 Feb 2021 09:19:45 +0100
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     mdalam@codeaurora.org
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        boris.brezillon@collabora.com, linux-mtd@lists.infradead.org,
        linux-kernel@vger.kernel.org, vigneshr@ti.com,
        sricharan@codeaurora.org
Subject: Re: [PATCH V4] mtd: rawnand: qcom: update last code word register
Message-ID: <20210212091945.304c2530@xps13>
In-Reply-To: <fe43b382fd48d7fb494dd66a4b5ac80a@codeaurora.org>
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        <20210210090144.GE19226@work>
        <20210211150759.506f3463@xps13>
        <fe43b382fd48d7fb494dd66a4b5ac80a@codeaurora.org>
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Hello,

mdalam@codeaurora.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@linaro.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@codeaurora.org>  
> >> >> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.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;

>   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