linux-kernel - Re: [PATCH v2] mfd: da9052-spi: change read-mask to write-mask

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Message-ID: <aN0mqU75onKEYSDg@zeus>
Date: Wed, 1 Oct 2025 16:03:37 +0300
From: Ian Ray <ian.ray@...ealthcare.com>
To: Marcus Folkesson <marcus.folkesson@...il.com>
Cc: Support Opensource <support.opensource@...semi.com>,
	Lee Jones <lee@...nel.org>, Axel Lin <axel.lin@...ics.com>,
	Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
	linux-kernel@...r.kernel.org, ian.ray@...ealthcare.com
Subject: Re: [PATCH v2] mfd: da9052-spi: change read-mask to write-mask

Hello Marcus,

On Wed, Sep 25, 2024 at 12:19:53PM +0200, Marcus Folkesson wrote:
> Driver has mixed up the R/W bit.
> The LSB bit is set on write rather than read.
> Change it to avoid nasty things to happen.
> 
> Fixes: e9e9d3973594 ("mfd: da9052: Avoid setting read_flag_mask for da9052-i2c driver")
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>

Your patch breaks DA9053 SPI communication (for me, at least) on the
6.1.y branch (I have not tested on master).

The datasheets [1] and [2] both refer to R/Wn in the SPI signalling.

What led to the assertion that "The LSB bit is set on write rather
than read."?

In the original code "config.read_flag_mask = 1;", is OR'd into the
buffer in regmap_set_work_buf_flag_mask.  This sets the "R" bit as
expected.

[1] DA9052 CFR0011-120-00 Rev 5, Revision 2.5, 13-Feb-2017, page 67.
[2] DA9053 DA9053-00-IDS2n_131017, page 54.

Blue skies,
Ian