linux-kernel - Re: [PATCH v2] bus: sunxi-rsb: Return correct data when mixing 16-bit and 8-bit reads

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Message-ID: <20200224110248.hpi3dhp3t7q56hmm@gilmour.lan>
Date:   Mon, 24 Feb 2020 12:02:48 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Ondrej Jirman <megous@...ous.com>
Cc:     linux-sunxi@...glegroups.com, Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>,
        Stephen Boyd <swboyd@...omium.org>,
        "moderated list:ARM/Allwinner sunXi SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] bus: sunxi-rsb: Return correct data when mixing
 16-bit and 8-bit reads

On Fri, Feb 21, 2020 at 09:27:26PM +0100, Ondrej Jirman wrote:
> When doing a 16-bit read that returns data in the MSB byte, the
> RSB_DATA register will keep the MSB byte unchanged when doing
> the following 8-bit read. sunxi_rsb_read() will then return
> a result that contains high byte from 16-bit read mixed with
> the 8-bit result.
>
> The consequence is that after this happens the PMIC's regmap will
> look like this: (0x33 is the high byte from the 16-bit read)
>
> % cat /sys/kernel/debug/regmap/sunxi-rsb-3a3/registers
> 00: 33
> 01: 33
> 02: 33
> 03: 33
> 04: 33
> 05: 33
> 06: 33
> 07: 33
> 08: 33
> 09: 33
> 0a: 33
> 0b: 33
> 0c: 33
> 0d: 33
> 0e: 33
> [snip]
>
> Fix this by masking the result of the read with the correct mask
> based on the size of the read. There are no 16-bit users in the
> mainline kernel, so this doesn't need to get into the stable tree.
>
> Signed-off-by: Ondrej Jirman <megous@...ous.com>
> Acked-by: Chen-Yu Tsai <wens@...e.org>

Applied, thanks!
Maxime

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