linux-kernel - Re: [PATCH v2] spi: bcm63xx: fix premature CS deassertion on RX-only transactions

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Message-ID: <aRpF3jRTs23YrPgC@sirena.co.uk>
Date: Sun, 16 Nov 2025 21:45:02 +0000
From: Mark Brown <broonie@...nel.org>
To: Hang Zhou <929513338@...com>
Cc: jonas.gorski@...il.com, linux-spi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] spi: bcm63xx: fix premature CS deassertion on RX-only
 transactions

On Mon, Nov 17, 2025 at 01:08:35AM +1100, Hang Zhou wrote:

> Fix this by writing 0xff dummy bytes into the TX FIFO for RX-only
> segments so that the number of bytes written to the FIFO matches the
> total message length seen by the controller.

Why 0xff?  The core's _MUST_TX handling writes 0x00 which feels a bit
more natural.  Given that this is PIO rather than DMA the memset_toio()
is going to be better than using the core (which is more for DMA).

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