Received-SPF: pass (google.com: domain of linux-kernel+bounces-63802-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Date: Tue, 13 Feb 2024 15:28:31 +0000
From: Mark Brown <broonie@kernel.org>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: =?iso-8859-1?Q?Th=E9o?= Lebrun <theo.lebrun@bootlin.com>,
	linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org,
	Dhruva Gole <d-gole@ti.com>,
	Gregory CLEMENT <gregory.clement@bootlin.com>,
	Vladimir Kondratiev <vladimir.kondratiev@mobileye.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Tawfik Bayouk <tawfik.bayouk@mobileye.com>
Subject: Re: [PATCH] spi: spi-mem: add statistics support to ->exec_op() calls
Message-ID: <69f023bb-2844-496f-9f3f-4e2e80129d33@sirena.org.uk>
References: <20240209-spi-mem-stats-v1-1-dd1a422fc015@bootlin.com>
 <b0844e5a-ee4b-4608-99a1-877660e01d57@linaro.org>
Precedence: bulk
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="MMftTTIZEnYjxm6P"
Content-Disposition: inline
In-Reply-To: <b0844e5a-ee4b-4608-99a1-877660e01d57@linaro.org>


--MMftTTIZEnYjxm6P
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Tue, Feb 13, 2024 at 12:39:02PM +0000, Tudor Ambarus wrote:
> On 2/9/24 13:51, Th=E9o Lebrun wrote:

> > +		if (!ret || ret !=3D -ENOTSUPP || ret !=3D -EOPNOTSUPP) {
> > +			spi_mem_add_op_stats(ctlr->pcpu_statistics, op, ret);
> > +			spi_mem_add_op_stats(mem->spi->pcpu_statistics, op, ret);
> > +

> Would be good to be able to opt out the statistics if one wants it.

> SPI NORs can write with a single write op maximum page_size bytes, which
> is typically 256 bytes. And since there are SPI NORs that can run at 400
> MHz, I guess some performance penalty shouldn't be excluded.

If we can cope with this sort of statistics collection in the networking
fast path we can probably cope with it for SPI too, the immediate
recording is all per CPU so I'd like to see some numbers showing that
it's a problem before worrying about it too much.  Even the people doing
things like saturating CAN buses haven't been raising it as a concern
for the regular SPI data path.  We could add a Kconfig if it's an issue.

--MMftTTIZEnYjxm6P
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmXLip8ACgkQJNaLcl1U
h9CTjQf/axznzzZjRR5HlbP310cOtEp7gWYv/5Py4bHDmJOsfZSb/gXBo/joMaRC
+HlD1aUoSw6g6DTwj6u5pD+8hNqmVOeUoM7Wy8b/xbDMAjZAfxM7W+AbtX+WiO0C
UyVGLSvUe4tTDiUJg6xhWQEFG6E8cZl7Sd3/LCcfl7Dy8XM+fQglFdhpnAka5Zqb
N6yB5zHdXBsEbAvUEUdwplckFjqecpAKTXSMyy5PlT7sdcgh8SfNszR0w58d6h2d
HkgYUQxmn0Q9tEZw569UhoR7i/9y/i+nUVTk51A0Byhh6pB58oQXTLwhm5Q2XABQ
vwKjnlRwwfk1sWk5jOz0eG0OiWnhog==
=kMnE
-----END PGP SIGNATURE-----

--MMftTTIZEnYjxm6P--