Messages in this thread | | | Subject | Re: [RFC PATCH] mtd: spi-nor: add support to non-uniform SPI NOR flash memories | From | Tudor Ambarus <> | Date | Thu, 24 May 2018 12:32:38 +0300 |
| |
Hi, Marek,
On 05/23/2018 03:54 PM, Marek Vasut wrote: > On 05/23/2018 02:52 PM, Tudor Ambarus wrote: >> Hi, Marek, > > Hi, > >> On 05/23/2018 12:56 PM, Marek Vasut wrote: >> [...] >>>>> [...] >>>>> >>>>>>>> + while (len) { >>>>>>>> + cmd = spi_nor_find_best_erase_cmd(map, region, addr, len); >>>>>>>> + if (!cmd) >>>>>>>> + return -EINVAL; >>>>>>> What would happen if you realize mid-way that you cannot erase some >>>>>>> sector , do you end up with partial erase ? >>>>>> Is this possible? In non-overlaid regions, the address is aligned with >>>>>> at least one of the erase commands, else -EINVAL. For overlaid regions >>>>>> alignment doesn't matter. But yes, if this is possible, in this case, >>>>>> this proposal will do a partial erase. >>>>> Shouldn't we fail up front instead ? >>>> It will be great if we can do this without having performance penalties. >>>> Can we loose the conditions for the last erase command? If one wants to >>>> erase 80k chunk starting from offset 0 and only 32k and 64k erase type >>>> are supported, can we erase 96k? >>> No. But can you maybe build a list of erase commands to be executed once >>> you validate that the erase can be performed for example ? >> >> My second choice was an array witch saves u8 opcode and u32 erasesize. >> There are flashes of 256MB, in the worst case scenario with 4k erase >> type, we will end up with 64K entries. > > Some RLE encoding might help here ?
Nice.
> >> How about enforcing the length to be multiple of mtd->erasesize, like we >> do in uniform_erase? With this, the problem disappears. > > What is the erase size for the 4k-sector 256MiB flash ?
S70FS01GS[1] is a 128 MByte flash with non-uniform erase support. It supports 4k and 256k erase types. I would have to enforce the address and the length to be multiple of 256k in order to vanish the issue. But the whole point of non-uniform erase will vanish too, I guess.
I don't have any other good :) idea, so I'll implement your suggestion with the list of erase commands and RLE encoding.
Thanks, ta
[1] http://www.cypress.com/file/215911/download
| |