[PATCH] mtd: rawnand: gpmi: Fix setting busy timeout setting

[Miquel Raynal]

On Tue, 2022-06-14 at 08:31:38 UTC, Sascha Hauer wrote:
> The DEVICE_BUSY_TIMEOUT value is described in the Reference Manual as:
> 
> | Timeout waiting for NAND Ready/Busy or ATA IRQ. Used in WAIT_FOR_READY
> | mode. This value is the number of GPMI_CLK cycles multiplied by 4096.
> 
> So instead of multiplying the value in cycles with 4096, we have to
> divide it by that value. Use DIV_ROUND_UP to make sure we are on the
> safe side, especially when the calculated value in cycles is smaller
> than 4096 as typically the case.
> 
> This bug likely never triggered because any timeout != 0 usually will
> do. In my case the busy timeout in cycles was originally calculated as
> 2408, which multiplied with 4096 is 0x968000. The lower 16 bits were
> taken for the 16 bit wide register field, so the register value was
> 0x8000. With 2970bf5a32f0 ("mtd: rawnand: gpmi: fix controller timings
> setting") however the value in cycles became 2384, which multiplied
> with 4096 is 0x950000. The lower 16 bit are 0x0 now resulting in an
> intermediate timeout when reading from NAND.
> 
> Fixes: b1206122069aa ("mtd: rawnand: gpmi: use core timings instead of an empirical derivation")
> Cc: stable at vger.kernel.org
> Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/fixes, thanks.

Miquel