Re: [PATCH 2/2] gpmi-nand: Add ERR007117 protection for nfc_apply_timings

[Miquel Raynal]

On Tue, 2021-11-02 at 20:20:22 UTC, Christian Eggers wrote:
> gpmi_io clock needs to be gated off when changing the parent/dividers of
> enfc_clk_root (i.MX6Q/i.MX6UL) respectively qspi2_clk_root (i.MX6SX).
> Otherwise this rate change can lead to an unresponsive GPMI core which
> results in DMA timeouts and failed driver probe:
> 
> [    4.072318] gpmi-nand 112000.gpmi-nand: DMA timeout, last DMA
> ...
> [    4.370355] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -110
> ...
> [    4.375988] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
> [    4.381524] gpmi-nand 112000.gpmi-nand: Error in ECC-based read: -22
> [    4.387988] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
> [    4.393535] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
> ...
> 
> Other than stated in i.MX 6 erratum ERR007117, it should be sufficient
> to gate only gpmi_io because all other bch/nand clocks are derived from
> different clock roots.
> 
> The i.MX6 reference manuals state that changing clock muxers can cause
> glitches but are silent about changing dividers. But tests showed that
> these glitches can definitely happen on i.MX6ULL. For i.MX7D/8MM in turn,
> the manual guarantees that no glitches can happen when changing
> dividers.
> 
> Co-developed-by: Stefan Riedmueller <s.riedmueller@xxxxxxxxx>
> Signed-off-by: Stefan Riedmueller <s.riedmueller@xxxxxxxxx>
> Signed-off-by: Christian Eggers <ceggers@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Acked-by: Han Xu <han.xu@xxxxxxx>

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

Miquel