Message ID | 4BF011D7.4010907@shemesh.biz |
---|---|
State | New, archived |
Headers | show |
2010/5/16 Shachar Shemesh: > The second problem I'm having with this driver is that it reports itself as > NOR flash. the response is: so what ? you havent described how this is problematic in any way. -mike
On Sun, May 16, 2010 at 15:04, Shachar Shemesh wrote: > Mike Frysinger wrote: >> 2010/5/16 Shachar Shemesh: >>> The second problem I'm having with this driver is that it reports itself as >>> NOR flash. >> >> the response is: so what ? you havent described how this is >> problematic in any way. > > Then why have flash type at all, if no-one cares? so your answer is "there is no problem with calling it NOR flash" if it looks like a duck, quacks like a duck, and walks like a duck, then why waste time calling it a DataDuck ? for all intents and purposes, all the kernel code/utilities that work with the flashes can treat these SPI flashes as NOR flashes and everything works fine. > Either way, the patch in my previous message is intended for inclusion. it isnt acceptable in the current format. so until you clean it up and submit it properly, nothing is going to happen. this of course ignores the errors in the patch like calling it DataFlash which you yourself clearly have shown is wrong. DataFlash is a special type of flash made by Atmel. it has properties which other SPI flashes do not. -mike
On Sun, May 16, 2010 at 15:55, Shachar Shemesh wrote: > Mike Frysinger wrote: >> so your answer is "there is no problem with calling it NOR flash" >> >> if it looks like a duck, quacks like a duck, and walks like a duck, >> then why waste time calling it a DataDuck ? for all intents and >> purposes, all the kernel code/utilities that work with the flashes can >> treat these SPI flashes as NOR flashes and everything works fine. > > Actually, that is not the case. Not even remotely. > > NOR flashes (and the m25p80 driver broadcasts it this way) have the ability > to change individual bytes (and, some flashes, individual bits). The SPI > flashes need to erase an entire block. NOR flashes are accessible via the > data bus, these require complicated SPI transactions. They neither quack nor > look anywhere near the same. you havent shown how the current behavior results in non-working flashes. you probably can claim that things dont work as optimally as possible according to the hardware, but as you noted, people work on what interests/annoys them rather than what other people report. > You might want to claim that they are NAND flashes, but, again, those are > somewhat different. Dataflashes are the closest these come to, as far as I > can tell. it doesnt make sense to lump SPI and NAND together because NAND allows for bad blocks. both NOR and SPI are guaranteed to be good throughout or the device is dead. so for all practical uses thus far, SPI and NOR operate the same way. >> it isnt acceptable in the current format. so until you clean it up >> and submit it properly, nothing is going to happen. > > Care to elaborate? Have never submitted patches to Linux before. I don't > mind RTFM, but please point me to the right manual. all Linux documentation is in the folder aptly named "Documentation", and from there it's a short hop to "SubmittingPatches". >> this of course ignores the errors in the patch like calling it >> DataFlash which you yourself clearly have shown is wrong. DataFlash >> is a special type of flash made by Atmel. it has properties which >> other SPI flashes do not. > > What would have really been necessary was a property saying "Serial flash". > I'm afraid I don't fully understand all of the consequence of adding such a > property, however. For one thing, this type is exported to user space. If > that's the only way to get this patch in, I'll do it, of course. I was > attempting to defer to your experience on the matter. since it is an exported ABI as you noted, the details need to be thought & hashed out before committing things as typically you cant go back. so why not start with a list of the differences that matter to the MTD layers where the NOR flashes differ from SPI flashes. emphasis here is on "where it matters to the MTD layers". if the MTD layers operate no differently whatsoever when encountering NOR and SPI flashes, then it doesnt really make sense to declare a new type for it. > I am not so sure about the "properties which other SPI flashes do not". Not, > at least, according to my research (which does not beat experience, but does > beat obscure abstract statements). iirc, dataflashes allow programming on individual bytes just like NOR flashes. most serial flashes (like the ST micro that started the SPI flash driver in the first place) have to be programmed on a page basis. dataflashes also have more flexible erase structures (4kb, 32kb, or 64kb) while ST micro can only be erased at 64kb sectors. my point is just that calling all SPI flashes "dataflashes" is inherently wrong since only Atmel makes dataflashes. it's also a bit funny since you started off the thread with the complaint that calling SPI flashes NOR flashes was wrong because SPI flashes arent NOR flashes. if you're going to declare a new category for SPI flashes, then it should be something that applies to all the current SPI flashes (just look in the m25p80.c driver to see all the ones supported). > Again, I'm trying to recruit the collective knowledge of this list in order > to do the right thing, not get into a fight. i'm just a schlub here. i'm not a MTD maintainer and wont be approving any patches. but this list suffers from responses, so i figured i'd throw something out i have a passing knowledge of. > I don't mind doing the work, > but I need help filling in the knowledge. I was told that newbies are > welcome, so long as they show a willingness not to dump their desires on > others, say by submitting actual patches..... that is indeed the way. but you cant really say "this patch is intended for inclusion" when (1) it is incorrectly formatted and (2) it has clearly unacceptable known bugs before the patch was even reviewed. -mike
On 17.05.2010 06:54, Mike Frysinger wrote: > On Sun, May 16, 2010 at 15:55, Shachar Shemesh wrote: > >> Mike Frysinger wrote: >> >>> so your answer is "there is no problem with calling it NOR flash" >>> >>> if it looks like a duck, quacks like a duck, and walks like a duck, >>> then why waste time calling it a DataDuck ? for all intents and >>> purposes, all the kernel code/utilities that work with the flashes can >>> treat these SPI flashes as NOR flashes and everything works fine. >>> >> Actually, that is not the case. Not even remotely. >> >> NOR flashes (and the m25p80 driver broadcasts it this way) have the ability >> to change individual bytes (and, some flashes, individual bits). The SPI >> flashes need to erase an entire block. NOR flashes are accessible via the >> data bus, these require complicated SPI transactions. They neither quack nor >> look anywhere near the same. >> > > you havent shown how the current behavior results in non-working > flashes. you probably can claim that things dont work as optimally as > possible according to the hardware, but as you noted, people work on > what interests/annoys them rather than what other people report. > ST M25P80 can change individual bytes. >> You might want to claim that they are NAND flashes, but, again, those are >> somewhat different. Dataflashes are the closest these come to, as far as I >> can tell. >> > > it doesnt make sense to lump SPI and NAND together because NAND allows > for bad blocks. both NOR and SPI are guaranteed to be good throughout > or the device is dead. so for all practical uses thus far, SPI and > NOR operate the same way. > Yes. >> I am not so sure about the "properties which other SPI flashes do not". Not, >> at least, according to my research (which does not beat experience, but does >> beat obscure abstract statements). >> > > iirc, dataflashes allow programming on individual bytes just like NOR > flashes. most serial flashes (like the ST micro that started the SPI > flash driver in the first place) have to be programmed on a page > basis. dataflashes also have more flexible erase structures (4kb, > 32kb, or 64kb) while ST micro can only be erased at 64kb sectors. > The ST M25P80 has a minimum write size of 1 bit (datasheet is a bit unclear, could also be 1 byte) and a maximum write size of 256 bytes. > my point is just that calling all SPI flashes "dataflashes" is > inherently wrong since only Atmel makes dataflashes. it's also a bit > funny since you started off the thread with the complaint that calling > SPI flashes NOR flashes was wrong because SPI flashes arent NOR > flashes. if you're going to declare a new category for SPI flashes, > then it should be something that applies to all the current SPI > flashes (just look in the m25p80.c driver to see all the ones > supported). > DataFlash is special because some of the chips have a user configurable page size: 512 or 528 Bytes per page. There's always the option of looking at how flashrom <http://www.flashrom.org/> handles those chips. flashrom an OS-independent userspace tool specialized on chips which are used for BIOS/firmware, but it handles some other flash chips as well. Regards, Carl-Daniel
I should point out that I have sent a retraction to the patch, but my messages got held up for moderation with "suspicious header" and no further explanation. I'm taking a wild guess as to the reason, in the hope that this message does get through. If it does, holding messages with "list does not support HTML or mixed format mail" will be a more useful error report. Carl-Daniel Hailfinger wrote: > > > > The ST M25P80 has a minimum write size of 1 bit (datasheet is a bit > unclear, could also be 1 byte) and a maximum write size of 256 bytes. > > I have not studies the M25P80 data sheet, but did the M25P32 and the MX25L6405D chips, and I believe all SPI flahses handled by the m25p80 driver behave the same in that regard (which is why they were clamped together to begin with). The minimal "program" length is 1 byte, but since a program can only change a 1 bit into 0, effectively, setting a word to "11...101...11", where the zero is at the bit you want to set, will program 1 bit. > > There's always the option of looking at how flashrom > <http://www.flashrom.org/> handles those chips. flashrom an > OS-independent userspace tool specialized on chips which are used for > BIOS/firmware, but it handles some other flash chips as well. > It lists them as "SPI", and the chip support page claims, at least for most of them, that it does not know how to erase them (http://www.flashrom.org/Supported_hardware). Shachar
On 18.05.2010 08:37, Shachar Shemesh wrote: > Carl-Daniel Hailfinger wrote: >> The ST M25P80 has a minimum write size of 1 bit (datasheet is a bit >> unclear, could also be 1 byte) and a maximum write size of 256 bytes. >> > I have not studies the M25P80 data sheet, but did the M25P32 and the > MX25L6405D chips, and I believe all SPI flahses handled by the m25p80 > driver behave the same in that regard (which is why they were clamped > together to begin with). > > The minimal "program" length is 1 byte, but since a program can only > change a 1 bit into 0, effectively, setting a word to "11...101...11", > where the zero is at the bit you want to set, will program 1 bit. Yes. The situation is a bit complicated. Some flash chips will not accept further writes to a location that has been written once even if those further writes would only change more bits to 0. Such chips have true 1 byte granularity. Other chips (and AFAIK the whole ST M25 series) can do at least two writes per byte location as long as the second write does not set any 0 bit to 1. >> There's always the option of looking at how flashrom >> <http://www.flashrom.org/> handles those chips. flashrom an >> OS-independent userspace tool specialized on chips which are used for >> BIOS/firmware, but it handles some other flash chips as well. >> > It lists them as "SPI", and the chip support page claims, at least for > most of them, that it does not know how to erase them > (http://www.flashrom.org/Supported_hardware). Thanks for pointing out that this page is misleading. The status "?" means that it is untested and should work. Only a read "No" means unsupported. I'll change the wiki to be more readable. Regards, Carl-Daniel
Index: drivers/mtd/devices/m25p80.c =================================================================== --- drivers/mtd/devices/m25p80.c (revision 3333) +++ drivers/mtd/devices/m25p80.c (working copy) @@ -212,7 +212,7 @@ { DEBUG(MTD_DEBUG_LEVEL3, "%s: %s %dKiB at 0x%08x\n", dev_name(&flash->spi->dev), __func__, - flash->mtd.erasesize / 1024, offset); + flash->mtd.writesize / 1024, offset); /* Wait until finished previous write command. */ if (wait_till_ready(flash)) @@ -255,7 +255,7 @@ /* sanity checks */ if (instr->addr + instr->len > flash->mtd.size) return -EINVAL; - div_u64_rem(instr->len, mtd->erasesize, &rem); + div_u64_rem(instr->len, mtd->writesize, &rem); if (rem) return -EINVAL; @@ -286,8 +286,8 @@ return -EIO; } - addr += mtd->erasesize; - len -= mtd->erasesize; + addr += mtd->writesize; + len -= mtd->writesize; } } @@ -831,9 +831,8 @@ else flash->mtd.name = dev_name(&spi->dev); - flash->mtd.type = MTD_NORFLASH; - flash->mtd.writesize = 1; - flash->mtd.flags = MTD_CAP_NORFLASH; + flash->mtd.type = MTD_DATAFLASH; + flash->mtd.flags = MTD_WRITEABLE; flash->mtd.size = info->sector_size * info->n_sectors; flash->mtd.erase = m25p80_erase; flash->mtd.read = m25p80_read; @@ -845,12 +844,13 @@ flash->mtd.write = m25p80_write; /* prefer "small sector" erase if possible */ - if (info->flags & SECT_4K) { + flash->mtd.erasesize = info->sector_size; + if (info->flags & SECT_4K && (info->sector_size%4096)==0 ) { flash->erase_opcode = OPCODE_BE_4K; - flash->mtd.erasesize = 4096; + flash->mtd.writesize = 4096; } else { flash->erase_opcode = OPCODE_SE; - flash->mtd.erasesize = info->sector_size; + flash->mtd.writesize = info->sector_size; } flash->mtd.dev.parent = &spi->dev; @@ -860,10 +860,11 @@ DEBUG(MTD_DEBUG_LEVEL2, "mtd .name = %s, .size = 0x%llx (%lldMiB) " - ".erasesize = 0x%.8x (%uKiB) .numeraseregions = %d\n", + ".erasesize = 0x%.8x (%uKiB) .writesize = 0x%.8x (%uKiB) .numeraseregions = %d\n", flash->mtd.name, (long long)flash->mtd.size, (long long)(flash->mtd.size >> 20), flash->mtd.erasesize, flash->mtd.erasesize / 1024, + flash->mtd.writesize, flash->mtd.writesize / 1024, flash->mtd.numeraseregions); if (flash->mtd.numeraseregions)