From: Ahmad Fatoum <firstname.lastname@example.org> To: email@example.com, firstname.lastname@example.org, Joakim.Tjernlund@infinera.com, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Cc: Chris Packham <email@example.com>, Brian Norris <firstname.lastname@example.org>, David Woodhouse <email@example.com>, firstname.lastname@example.org, email@example.com, "firstname.lastname@example.org" <email@example.com>, Pengutronix Kernel Team <firstname.lastname@example.org>, email@example.com, Shaohui.Xie@nxp.com Subject: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1 Date: Mon, 13 Dec 2021 14:24:39 +0100 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) Hi, I've been investigating a breakage on a PowerPC MPC8313: The SoC is connected via the "Enhanced Local Bus Controller" to a 8-bit-parallel S29GL064N flash, which is represented as a memory-mapped cfi-flash. The regression began in v4.17-rc1 with dfeae1073583 ("mtd: cfi_cmdset_0002: Change write buffer to check correct value") and causes all flash write accesses on the hardware to fail. Example output after v5.1-rc2: root@host:~# mount -t jffs2 /dev/mtdblock0 /mnt MTD do_write_buffer_wait(): software timeout, address:0x000c000b. jffs2: Write clean marker to block at 0x000c0000 failed: -5 This issue still persists with v5.16-rc. Reverting aforementioned patch fixes it, but I am still looking for a change that keeps both Tokunori's and my hardware happy. What Tokunori's patch did is that it strengthened the success condition for flash writes: - Prior to the patch, DQ polling was done until bits stopped toggling. This was taken as an indicator that the write succeeded and was reported up the stack. i.e. success condition is chip_ready() - After the patch, polling continues until the just written data is actually read back, i.e. success condition is chip_good() This new condition never holds for me, when DQ stabilizes, it reads 0xFF, never the just written data. The data is still written and can be read back on subsequent reads, just not at that point of time in the poll loop. We haven't had write issues for the years predating that patch. As the regression has been mainline for a while, I am wondering what about my setup that makes it pop up here, but not elsewhere? I consulted the data sheet and found Figure 27, which describes DQ polling during embedded algorithms. DQ switches from status output to "True" (I assume True == all bits set == 0xFF) until CS# is reasserted. I compared with another chip's datasheet, and it (Figure 8.4) doesn't describe such an intermittent "True" state. In any case, the driver polls a few hundred times, however, before giving up, so there should be enough CS# toggles. Locally, I'll revert this patch for now. I think accepting 0xFF as a success condition may be appropriate, but I don't yet have the rationale to back it up. I am investigating this some more, probably with a logic trace, but I wanted to report this in case someone has pointers and in case other people run into the same issue. Cheers, Ahmad  Prior to d9b8a67b3b95 ("mtd: cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer") first included with v5.1-rc2, failing writes just hung indefinitely in kernel space. That's fixed, but the writes still fail. : 001-98525 Rev. *B, https://www.infineon.com/dgdl/Infineon-S29GL064N_S29GL032N_64_Mbit_32_Mbit_3_V_Page_Mode_MirrorBit_Flash-DataSheet-v03_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ed556fd548b : https://www.mouser.com/datasheet/2/268/SST39VF1601C-SST39VF1602C-16-Mbit-x16-Multi-Purpos-709008.pdf Note that "true data" means valid data here, not all bits one. -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
next reply other threads:[~2021-12-13 13:24 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-13 13:24 Ahmad Fatoum [this message] 2021-12-14 7:23 ` Thorsten Leemhuis 2021-12-15 17:34 ` Tokunori Ikegami 2022-01-20 13:00 ` Thorsten Leemhuis 2022-01-28 12:55 ` Ahmad Fatoum 2022-01-29 18:01 ` Tokunori Ikegami 2022-02-07 14:28 ` Ahmad Fatoum 2022-02-13 16:47 ` Tokunori Ikegami 2022-02-14 16:22 ` Ahmad Fatoum 2022-02-14 18:46 ` Tokunori Ikegami 2022-02-20 12:22 ` Tokunori Ikegami 2022-03-04 11:11 ` Ahmad Fatoum 2022-03-06 15:49 ` Tokunori Ikegami 2022-03-08 9:44 ` Ahmad Fatoum 2022-03-08 16:13 ` Tokunori Ikegami 2022-03-08 16:23 ` Ahmad Fatoum 2022-03-08 16:40 ` Tokunori Ikegami
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