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SubjectRe: [RESEND] mtd: spi-nor: Fix Cadence QSPI RCU Schedule Stall
Date
Miquel,

On 08/16/2019 01:55 AM, thor.thayer@linux.intel.com wrote:
> External E-Mail
>
>
> From: Thor Thayer <thor.thayer@linux.intel.com>
>
> The current Cadence QSPI driver sometimes caused a
> "rcu_sched self-detected stall" while writing large files.
>
> Stall Report:
> '# mtd_debug write /dev/mtd1 0 48816464 blob.img
> [ 1815.454227] rcu: INFO: rcu_sched self-detected stall on CPU
> [ 1815.459789] rcu: 0-....: (2099 ticks this GP) idle=8c6/1/0x40000002
> softirq=6492/6492 fqs=935
> [ 1815.468442] rcu: (t=2100 jiffies g=8749 q=247)
> <snip> (abbreviated backtrace)
> [ 1815.772086] [<c05a3ea0>] (cqspi_exec_flash_cmd) (cqspi_read_reg)
> [ 1815.786203] [<c05a5488>] (cqspi_read_reg) from (read_sr)
> [ 1815.803790] [<c05a0330>] (read_sr) from
> (spi_nor_wait_till_ready_with_timeout)
> [ 1815.816610] [<c05a182c>] (spi_nor_wait_till_ready_with_timeout) from
> (spi_nor_write+0x104/0x1d0)
> [ 1815.836791] [<c05a1a44>] (spi_nor_write) from (part_write+0x50/0x58)
> <snip>
> [ 1815.997961] cadence-qspi ff809000.spi: Flash command execution timed out.
> [ 1816.004733] error -110 reading SR
> file_to_flash: write, size 0x2e8e150, n 0x2e8e150
> write(): Connection timed out
>
> This was caused by a tight loop in cqspi_wait_for_bit(). Fix by using
> readl_relaxed_poll_timeout() which sleeps 10us while polling a register.
>
> Fit onto 80 character line by truncating the bool clear parameter
>
> Fixes: 140623410536 ("mtd: spi-nor: Add driver for Cadence Quad SPI Flash Controller")
> Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>

Probably this is a good candidate for mtd/fixes.

Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>

> ---
> drivers/mtd/spi-nor/cadence-quadspi.c | 19 +++++--------------
> 1 file changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 67f15a1f16fd..7bef63947b29 100644
> --- a/drivers/mtd/spi-nor/cadence-quadspi.c
> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
> @@ -13,6 +13,7 @@
> #include <linux/errno.h>
> #include <linux/interrupt.h>
> #include <linux/io.h>
> +#include <linux/iopoll.h>
> #include <linux/jiffies.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> @@ -241,23 +242,13 @@ struct cqspi_driver_platdata {
>
> #define CQSPI_IRQ_STATUS_MASK 0x1FFFF
>
> -static int cqspi_wait_for_bit(void __iomem *reg, const u32 mask, bool clear)
> +static int cqspi_wait_for_bit(void __iomem *reg, const u32 mask, bool clr)
> {
> - unsigned long end = jiffies + msecs_to_jiffies(CQSPI_TIMEOUT_MS);
> u32 val;
>
> - while (1) {
> - val = readl(reg);
> - if (clear)
> - val = ~val;
> - val &= mask;
> -
> - if (val == mask)
> - return 0;
> -
> - if (time_after(jiffies, end))
> - return -ETIMEDOUT;
> - }
> + return readl_relaxed_poll_timeout(reg, val,
> + (((clr ? ~val : val) & mask) == mask),
> + 10, CQSPI_TIMEOUT_MS * 1000);
> }
>
> static bool cqspi_is_idle(struct cqspi_st *cqspi)
>
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