linux-kernel - Re: [PATCH v1 01/12] nvmem: microchip-otpc: Avoid writing a write-only register

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Message-ID: <f514b2af-e2bc-4ea3-8630-937c6c05dc31@tuxon.dev>
Date: Sat, 24 Aug 2024 18:51:59 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Alexander Dahl <ada@...rsis.com>
Cc: Christian Melki <christian.melki@...ata.com>,
 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
 "moderated list:MICROCHIP OTPC DRIVER"
 <linux-arm-kernel@...ts.infradead.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 01/12] nvmem: microchip-otpc: Avoid writing a
 write-only register

Hi, ALexander,

On 21.08.2024 13:59, Alexander Dahl wrote:
> The OTPC Control Register (OTPC_CR) has just write-only members.
> Reading from that register leads to a warning in OTPC Write Protection
> Status Register (OTPC_WPSR) in field Software Error Type (SWETYP) of
> type READ_WO (A write-only register has been read (warning).)
> 
> Just create the register write content from scratch is sufficient here.
> 
> Signed-off-by: Alexander Dahl <ada@...rsis.com>

Maybe worth a Fixes tag here.

> ---
>  drivers/nvmem/microchip-otpc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvmem/microchip-otpc.c b/drivers/nvmem/microchip-otpc.c
> index 7cf81738a3e0..03e60b99f2c9 100644
> --- a/drivers/nvmem/microchip-otpc.c
> +++ b/drivers/nvmem/microchip-otpc.c
> @@ -82,7 +82,7 @@ static int mchp_otpc_prepare_read(struct mchp_otpc *otpc,
>  	writel_relaxed(tmp, otpc->base + MCHP_OTPC_MR);
>  
>  	/* Set read. */
> -	tmp = readl_relaxed(otpc->base + MCHP_OTPC_CR);
> +	tmp = 0;
>  	tmp |= MCHP_OTPC_CR_READ;
>  	writel_relaxed(tmp, otpc->base + MCHP_OTPC_CR);

	writel_relaxed(MCHP_OTPC_CR_READ, otpc->base + MCHP_OTPC_CR);

should be enough here.

Thank you,
Claudiu Beznea

>