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From: Vladimir Oltean <vladimir.oltean@nxp.com>
To: Colin Foster <colin.foster@in-advantage.com>
Cc: linux-kernel@vger.kernel.org, Lee Jones <lee@kernel.org>
Subject: Re: [PATCH v1 mfd] mfd: ocelot-spi: fix bulk read
Date: Wed, 22 Mar 2023 17:58:29 +0200	[thread overview]
Message-ID: <20230322155829.uecwlv23r7plgok4@skbuf> (raw)
In-Reply-To: <ZBsinMmfbglf2w8W@colin-ia-desktop>

On Wed, Mar 22, 2023 at 08:45:32AM -0700, Colin Foster wrote:
> The chip itself doesn't support bulk reads. Every register read must be
> "Chip Select \" > "Read+Address Command" > "Padding" > "One Register Value" >
> "Chip Select /"
> 
> Figure 74 of [1] shows "SI Read Timing in Fast Mode", but that is when
> the VSC751X is the SPI controller, not a SPI endpoint. i.e. when the
> VSC751X is reading _from_ an external flash chip. It also has a blurb
> about "After reading address n, the SI boot controller automatically
> continues reading address n+1".
> 
> Figure 63 shows "Read Sequence for One-Byte Padding" which is actually
> done when an external CPU is reading _from_ the VSC751X devices. There
> is no suggestion that address n+1 will be returned in this scenario.
> 
> [1] https://ww1.microchip.com/downloads/en/DeviceDoc/VMDS-10489.pdf
> 
> I can update the commit message as needed.

I have no further comment. From my perspective, resending the patch is
not needed.

  reply	other threads:[~2023-03-22 15:58 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-22 14:11 Colin Foster
2023-03-22 15:25 ` Vladimir Oltean
2023-03-22 15:45   ` Colin Foster
2023-03-22 15:58     ` Vladimir Oltean [this message]
2023-03-30 12:37 ` Lee Jones

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