linux-kernel - Re: [PATCH] mtd: rawnand: marvell: ensure timing values are written

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Message-ID: <20230523113930.48c631d4@xps-13>
Date:   Tue, 23 May 2023 11:39:30 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc:     richard@....at, vigneshr@...com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: rawnand: marvell: ensure timing values are written

Hi Chris,

chris.packham@...iedtelesis.co.nz wrote on Tue, 23 May 2023 15:21:03
+1200:

> When new timing values are calculated in marvell_nfc_setup_interface()
> ensure that they will be applied in marvell_nfc_select_target() by
> clearing the selected_chip pointer.
> 
> Suggested-by: Miquel Raynal <miquel.raynal@...tlin.com>
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>

I believe this patch deserves Fixes+Cc:stable?

> ---
> 
> Notes:
>     This at least gets me to a point where I can illustrated the problem
>     reported to me. It appears that despite the chip correctly reporting
>     support for SDR timing modes up to 4 the observed tWC is 20ns. I've not
>     seen any actual problem running in this state the only complaint is that
>     the datasheet says the minimum tWC is 25ns.
>     
>     If I make a change to my bootloader such that the NAND Clock Frequency
>     Select bit (0xF2440700:0) to 1 before booting the kernel _and_ I remove
>     the extra factor of 2 from the period_ns calculation I observe tWC of
>     about 60ns. If I don't remove the factor of 2 the NAND interface doesn't
>     work (can't write BBT).
> 
>  drivers/mtd/nand/raw/marvell_nand.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/marvell_nand.c b/drivers/mtd/nand/raw/marvell_nand.c
> index afb424579f0b..3b5e4d5d220f 100644
> --- a/drivers/mtd/nand/raw/marvell_nand.c
> +++ b/drivers/mtd/nand/raw/marvell_nand.c
> @@ -2457,6 +2457,12 @@ static int marvell_nfc_setup_interface(struct nand_chip *chip, int chipnr,
>  			NDTR1_WAIT_MODE;
>  	}
>  
> +	/*
> +	 * Reset nfc->selected_chip so the next command will cause the timing
> +	 * registers to be restored in marvell_nfc_select_target().
> +	 */

s/restored/updated/ ?

Restored feels like the content vanished.

> +	nfc->selected_chip = NULL;
> +
>  	return 0;
>  }
>  


Thanks,
Miquèl