Messages in this thread | | | Subject | Re: [PATCH] mtd: spi-nor: Fix Cadence QSPI page fault kernel panic | From | Thor Thayer <> | Date | Wed, 14 Nov 2018 09:25:08 -0600 |
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Hi Vignesh,
On 11/14/18 6:00 AM, Vignesh R wrote: > Hi, > > On 13/11/18 11:02 PM, thor.thayer@linux.intel.com wrote: >> From: Thor Thayer <thor.thayer@linux.intel.com> >> >> The current Cadence QSPI driver caused a kernel panic sporadically >> when writing to QSPI. The problem was caused by writing more bytes >> than needed because the QSPI operated on 4 bytes at a time. >> <snip> >> [ 11.202044] Unable to handle kernel paging request at virtual address bffd3000 >> [ 11.209254] pgd = e463054d >> [ 11.211948] [bffd3000] *pgd=2fffb811, *pte=00000000, *ppte=00000000 >> [ 11.218202] Internal error: Oops: 7 [#1] SMP ARM >> [ 11.222797] Modules linked in: >> [ 11.225844] CPU: 1 PID: 1317 Comm: systemd-hwdb Not tainted 4.17.7-d0c45cd44a8f >> [ 11.235796] Hardware name: Altera SOCFPGA Arria10 >> [ 11.240487] PC is at __raw_writesl+0x70/0xd4 >> [ 11.244741] LR is at cqspi_write+0x1a0/0x2cc >> </snip> >> On a page boundary limit the number of bytes copied from the tx buffer >> to remain within the page. >> >> This patch uses a temporary buffer to hold the 4 bytes to write and then >> copies only the bytes required from the tx buffer. A min() function is >> used to limit the length to prevent buffer indexing overflows. >> >> Reported-by: Adrian Amborzewicz <adrian.ambrozewicz@intel.com> >> Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com> >> --- >> drivers/mtd/spi-nor/cadence-quadspi.c | 19 ++++++++++++++++--- >> 1 file changed, 16 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c >> index d846428ef038..3659d94b4d2f 100644 >> --- a/drivers/mtd/spi-nor/cadence-quadspi.c >> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c >> @@ -644,9 +644,23 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor, loff_t to_addr, >> ndelay(cqspi->wr_delay); >> >> while (remaining > 0) { >> + size_t write_words, mod_bytes; >> + >> write_bytes = remaining > page_size ? page_size : remaining; >> - iowrite32_rep(cqspi->ahb_base, txbuf, >> - DIV_ROUND_UP(write_bytes, 4)); >> + write_words = write_bytes / 4; >> + mod_bytes = write_bytes % 4; >> + /* Write 4 bytes at a time then single bytes. */ >> + if (write_words) { >> + iowrite32_rep(cqspi->ahb_base, txbuf, write_words); >> + txbuf += (write_words * 4); >> + } >> + if (mod_bytes) { >> + unsigned int temp = 0xFFFFFFFF; >> + >> + memcpy(&temp, txbuf, min(sizeof(temp), mod_bytes)); > > Sorry, I dont understand why min() is required here since: > mod_bytes = write_bytes % 4; > Doesn't that ensure mod_bytes < sizeof(temp)? >
Yes, good point. I was being overly cautious with the memcpy buffers. I will re-spin and re-submit. Thanks!
>> + iowrite32(temp, cqspi->ahb_base); >> + txbuf += mod_bytes; >> + } >> >> if (!wait_for_completion_timeout(&cqspi->transfer_complete, >> msecs_to_jiffies(CQSPI_TIMEOUT_MS))) { >> @@ -655,7 +669,6 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor, loff_t to_addr, >> goto failwr; >> } >> >> - txbuf += write_bytes; >> remaining -= write_bytes; >> >> if (remaining > 0) >> >
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