linux-kernel - Re: [PATCH 2/2] gpmi-nand: Add ERR007117 protection for nfc_apply

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Date:   Fri, 19 Nov 2021 19:43:39 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Christian Eggers <ceggers@...i.de>,
        Michael Trimarchi <michael@...rulasolutions.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Stefan Riedmueller <S.Riedmueller@...tec.de>,
        Han Xu <han.xu@....com>, Greg Ungerer <gerg@...nel.org>
Cc:     Sascha Hauer <s.hauer@...gutronix.de>,
        Christian Hemp <C.Hemp@...tec.de>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "Stefan Riedmueller" <s.riedmueller@...tec.de>,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/2] gpmi-nand: Add ERR007117 protection for nfc_apply_timings

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@...tec.de>
> Signed-off-by: Stefan Riedmueller <s.riedmueller@...tec.de>
> Signed-off-by: Christian Eggers <ceggers@...i.de>
> Cc: stable@...r.kernel.org
> Acked-by: Han Xu <han.xu@....com>

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

Miquel