Messages in this thread | | | Subject | Re: [PATCH v8] mtd: spi-nor: Add support for S3AN spi-nor devices | From | Marek Vasut <> | Date | Thu, 1 Dec 2016 19:11:24 +0100 |
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On 12/01/2016 06:52 PM, Ricardo Ribalda Delgado wrote: > Hi Marek
Hi,
> Thanks for your review > > On Thu, Dec 1, 2016 at 5:05 PM, Marek Vasut <marek.vasut@gmail.com> wrote: >> >> On 11/24/2016 05:56 PM, Ricardo Ribalda Delgado wrote: > >>> +#define SPI_S3AN BIT(10) /* >>> + * Xilinx Spartan 3AN In-System Flash >>> + * (MFR cannot be used for probing >>> + * because it has the same value as >>> + * ATMEL flashes) >>> + */ >> >> I have possibly off-topic question. Altera has something very similar -- >> EPCS/EPCQ flash which cannot be detected using standard READID . >> Would this patch help with supporting those degenerate flashes too? >> >>> }; >>> > > I dont know, but I love the term degenerated flash, please let me use it :)
Hehe. It'd be great to know whether we don't have a possibility for a generic usecase here. Can you briefly check that ?
>>> for (i = 0; i < len; ) { >>> ssize_t written; >>> + loff_t addr = to + i; >>> + >>> + if (hweight32(nor->page_size) == 1) { >>> + page_offset = addr & (nor->page_size - 1); >>> + } else { >>> + uint64_t aux = addr; >>> >>> - page_offset = (to + i) & (nor->page_size - 1); >>> + page_offset = do_div(aux, nor->page_size); >>> + } >> >> Why is this part necessary ? > > If page_size is not a power of 2 (264,528), the & (size-1) operation > for getting the offset does not work, you need to do a real modulus.
Aaah, now it makes sense. Ew, but all right, thanks for clarifying. This could use a comment, somewhere along these lines.
>>> + >>> + /* Flash in Power of 2 mode */ >>> + if (val & XSR_PAGESIZE) { >>> + nor->page_size = (nor->page_size == 264) ? 256 : 512; >> >> 264 is due to some ECC ? > > The flash can be in standard mode or in power of two mode. You need to > check the status register to know if the chip is in one mode or the > other. > > The flash is in standard mode from factory, you can change the mode to > power of two, but the data is corrupted and you cannot change back to > standard mode. > > I guess they are using some bits reserved to ECC for data and that way > you can squeeze some bits for user data.
OK, comment could help clarify this, so please add one.
>>> + nor->mtd.writebufsize = nor->page_size; >>> + nor->mtd.size = 8 * nor->page_size * info->n_sectors; >>> + nor->mtd.erasesize = 8 * nor->page_size; >>> + } else { >>> + nor->flags |= SNOR_F_S3AN_ADDR_DEFAULT; >>> + } >>> + >>> + return 0; >>> +} >> >> [...] >> >> -- >> Best regards, >> Marek Vasut > > Thanks Again > > > >
-- Best regards, Marek Vasut
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