From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: Depreciated spi_master.transfer and "prepared spi messages" for an optimized pipelined-SPI-DMA-driver Date: Thu, 7 Nov 2013 20:31:27 +0000 Message-ID: <20131107203127.GB2493@sirena.org.uk> References: <20131104184511.GR2493@sirena.org.uk> <5A55A832-5313-499C-A483-BF5A6649D69D@sperl.org> <20131106094854.GF11602@sirena.org.uk> <844EDAEA-3FDC-48D0-B59E-CECC0A83761E@sperl.org> <20131106113219.GJ11602@sirena.org.uk> <20131106162410.GB2674@sirena.org.uk> <3B0EDE3F-3386-4879-8D89-2E4577860073@sperl.org> <20131106232605.GC2674@sirena.org.uk> <72D635F5-4229-4D78-8AA3-1392D5D80127@sperl.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kD5A6s5fH5u0LDZc" Cc: linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Martin Sperl Return-path: Content-Disposition: inline In-Reply-To: <72D635F5-4229-4D78-8AA3-1392D5D80127-d5rIkyn9cnPYtjvyW6yDsg@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: --kD5A6s5fH5u0LDZc Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Nov 07, 2013 at 01:43:39AM +0100, Martin Sperl wrote: > The problem is that you intend to do prepare/unprepare transparently. Please be more concrete and specific, I'm still really struggling to understand what your concern is. Please do also reply to what's being said rather than deleting the entire mail, it makes it easier to follow the thread of conversation. > OK - but I see problems with heuristics on when it is safe to assume > that a message has not been changed since the last call (either xfers > or tx/rx_buff pointer). If it has not changed then we can use the cached= =20 > computations from the previous step ( equivalent to prepared). Why would the SPI core assume that a message just passed into it is a previously submitted message which has not been changed? This seems like something which would add extra complexity to the implementation over the simpler approach of just treating each new message as a new one. Bear in mind that the goals here are to refactor the code so that the DMA mapping is factored out of the drivers (and can be moved so that it runs in parallel with transfers), factor out the handling of /CS and in general the handling of message breaks and avoid all the drivers having to implement the logic required to push transfers from interrupt context where possible. --kD5A6s5fH5u0LDZc Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSe/ibAAoJELSic+t+oim9CbYP/0FO6mFS1mh98TLwieT+UiJU ldU5q4tKik74z7gM5DF3yBH/uyIMYVASv/wCp88ntUVa7lOC/W22vl6MxP+Qcvja YuX6Bn1Hp+MnxJqL5rKKGF3FhTZaC+l0imQQuLfm9+rMIsobTIDnh3KYMo3aacHh emM5AjjxnodckX857vdk5KDziuS0fZtmelno7FPCWTjFhqQhbE+67mLytDpADZSt Y1fRmBVTNvLePG23p2i9elk1tpnmNRB/zT+BtrjgcRI/xMmqbCCKbm8i8bG84WfF hMDSSHIPJOctEBi84Y6YQ6fv66K3fVdrK8rkEViGATkzrkRrkP5JlXp25pAkw4e3 LbgDKsPEQssbyVYpu1PXxVFQQq3NRbuUzTl+MZTHpcYVLcw8UtwrdecC2+wpoTR3 ZcZHASbaOqpNjtBPTwXgYRpFP5zbX0JS8uZUf1Xg40LAsKbziR0GHPGZTnRbhUgD 3nvEwbFNlUVSRtAuzfwkIBeUrIkujCDfDaarAFyw99mdb1QasGD6ub+fp0HAKV6A G7/c/YEs6p2rLmTSxZ7JGCqJKPGV9p0o6lWiV0uauUHaiV1Ca1d/o5/KphRFAxFL jpXomYTIkzDb8+Q8oIQYgJpSl827y5P0MZFGUwZACdXHe1NmMu6t1jELiiecSYFf eOxkMhm5fv58CrQATFyk =6tOT -----END PGP SIGNATURE----- --kD5A6s5fH5u0LDZc-- -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html