[PATCH v2] mtd: spi-nor: Fix the spi_nor_read() when config SPI_STACKED_PARALLEL is enabled

[Abbarapu, Venkatesh]

> -----Original Message-----
> From: Marek Vasut <marex at denx.de>
> Sent: Monday, December 16, 2024 4:06 PM
> To: Abbarapu, Venkatesh <venkatesh.abbarapu at amd.com>; u-boot at lists.denx.de;
> tudor.ambarus at linaro.org; j-humphreys at ti.com
> Cc: Simek, Michal <michal.simek at amd.com>; jagan at amarulasolutions.com;
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> Subject: Re: [PATCH v2] mtd: spi-nor: Fix the spi_nor_read() when config
> SPI_STACKED_PARALLEL is enabled
> 
> On 12/16/24 5:16 AM, Abbarapu, Venkatesh wrote:
> 
> [...]
> 
> >>> +++ b/drivers/mtd/spi/spi-nor-core.c
> >>> @@ -1140,7 +1140,7 @@ static int spi_nor_erase(struct mtd_info *mtd,
> >>> struct
> >> erase_info *instr)
> >>>    				nor->spi->flags &= ~SPI_XFER_U_PAGE;
> >>>    		}
> >>>    #ifdef CONFIG_SPI_FLASH_BAR
> >>> -		ret = write_bar(nor, addr);
> >>> +		ret = write_bar(nor, offset);
> >>
> >> This change is really inobvious, the code above likely needs to be
> >> compiled out if the SPI_STACKED_PARALLEL stuff is disabled ?
> >
> > In the spi_nor_erase()
> > 	offset = addr;
> > 	if(PARALLEL)
> > 		offset/=2;
> > 	so for parallel or single configuration we need to pass "offset" to write_bar()
> > 	write_bar(nor, offset");
> 
> The code above likely needs to be compiled out if the SPI_STACKED_PARALLEL
> stuff is disabled ?
> 
> [...]
> 
Already the code here is being checked with the flags SNOR_F_HAS_PARALLEL and SNOR_F_HAS_STACKED. Do you want to add the check SPI_STACKED_PARALLEL apart from these flags?


> >> If I look at this change with 'git show -w' , the change looks like this:
> >>
> >> "
> >>    #ifdef CONFIG_SPI_FLASH_BAR
> >> +               u32 remain_len;
> >> +
> >>                   ret = write_bar(nor, offset);
> >>                   if (ret < 0)
> >>                           return log_ret(ret);
> >> +               remain_len = (SZ_16M * (nor->bank_curr + 1)) - offset;
> >> +               if (len < remain_len)
> >> +                       read_len = len;
> >> +               else
> >> +                       read_len = remain_len;
> >>    #endif
> >> -
> >> +               if (CONFIG_IS_ENABLED(SPI_STACKED_PARALLEL)) {
> >>                           if (len < rem_bank_len)
> >>                                   read_len = len;
> >>                           else
> >>                                   read_len = rem_bank_len;
> >> -
> >> +               }
> >>                   if (read_len == 0)
> >>                           return -EIO; "
> >>
> >> Why is there this part of code twice now, ifdeffed out differently in each case ?
> >>
> >> "
> >>                           if (len < rem_bank_len)
> >>                                   read_len = len;
> >>                           else
> >>                                   read_len = rem_bank_len; "
> >
> > For parallel/stacked configuration and address width the "rem_bank_len" will vary
> and as we don't want to disturb the default read functionality added the ifdef
> separately.
> What would happen if both SPI_FLASH_BAR and SPI_STACKED_PARALLEL are
> enabled on a system that only has one SPI NOR attached
> (non-stacked/parallel) ? I noticed the second "copy" of the code behaves slightly
> differently in the else branch, so does that mean this would break such setup ?

If both SPI_FLASH_BAR and SPI_STACKED_PARALLEL are enabled, the "rem_bank_len" manipulation is done under the CONFIG_IS_ENABLED(SPI_STACKED_PARALLEL) code and this won't break any default functionality.

Thanks
Venkatesh