From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [RFC] dmaengine: rcar-dmac: set scatter/gather max segment size From: Wolfram Sang Message-Id: <20180914133518.GA1413@kunai> Date: Fri, 14 Sep 2018 15:35:18 +0200 To: Geert Uytterhoeven Cc: Wolfram Sang , dmaengine@vger.kernel.org, Linux-Renesas , Yoshihiro Shimoda List-ID: SGkgR2VlcnQsCgo+ID4gKyAgICAgICBkbWFjLT5kZXYtPmRtYV9wYXJtcyA9ICZkbWFjLT5wYXJt czsKPiA+ICsgICAgICAgZG1hX3NldF9tYXhfc2VnX3NpemUoZG1hYy0+ZGV2LCAweDAxMDAwMDAw KTsKPiAKPiBUaGF0IGlzIG9uZSB0b28gbXVjaCwgY2ZyLgo+IAo+ICAgICBkcml2ZXJzL2RtYS9z aC9yY2FyLWRtYWMuYzojZGVmaW5lIFJDQVJfRE1BVENSX01BU0sgICAgICAgICAgICAgMHgwMGZm ZmZmZgoKSSBzZWUuIFdpbGwgZml4IGFuZCBzZW5kIGFuIHVwZGF0ZWQgcGF0Y2guIE5pY2UgdG8g c2VlIHRoYXQgSSB3YXMgbm90CnRvdGFsbHkgd3JvbmcgYnV0IGp1c3Qgb2ZmLWJ5LW9uZS4KCj4g QW5kIHllcywgdGhpcyBkZXBlbmRzIG9uIHRoZSBkYXRhIGxlbmd0aCwgd2hpY2ggaXMgbm90IGtu b3duIGF0IHByb2JlIHRpbWUuCj4gT2YgY291cnNlLCBkbWFfc2V0X21heF9zZWdfc2l6ZShkbWFj LT5kZXYsIFJDQVJfRE1BVENSX01BU0spCj4gc2hvdWxkIGJlIHNhZmUsIGFsYmVpdCAoc2xpZ2h0 bHkpIHN1Ym9wdGltYWwuCgpUcnVlLiBCdXQgc3RpbGwgKndheSogYmV0dGVyIHRoYW4gdGhlIGN1 cnJlbnQgZGVmYXVsdCBvZiA2NEsuCgpUaGFua3MgZm9yIHRoZSBoZWFkcyB1cCEKClJlZ2FyZHMs CgogICBXb2xmcmFtCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sauhun.de ([88.99.104.3]:44932 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727623AbeINStx (ORCPT ); Fri, 14 Sep 2018 14:49:53 -0400 Date: Fri, 14 Sep 2018 15:35:18 +0200 From: Wolfram Sang To: Geert Uytterhoeven Cc: Wolfram Sang , dmaengine@vger.kernel.org, Linux-Renesas , Yoshihiro Shimoda Subject: Re: [RFC PATCH] dmaengine: rcar-dmac: set scatter/gather max segment size Message-ID: <20180914133518.GA1413@kunai> References: <20180913145256.12261-1-wsa+renesas@sang-engineering.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="envbJBWh7q8WU6mo" Content-Disposition: inline In-Reply-To: Sender: linux-renesas-soc-owner@vger.kernel.org List-ID: --envbJBWh7q8WU6mo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Geert, > > + dmac->dev->dma_parms =3D &dmac->parms; > > + dma_set_max_seg_size(dmac->dev, 0x01000000); >=20 > That is one too much, cfr. >=20 > drivers/dma/sh/rcar-dmac.c:#define RCAR_DMATCR_MASK 0x00f= fffff I see. Will fix and send an updated patch. Nice to see that I was not totally wrong but just off-by-one. > And yes, this depends on the data length, which is not known at probe tim= e. > Of course, dma_set_max_seg_size(dmac->dev, RCAR_DMATCR_MASK) > should be safe, albeit (slightly) suboptimal. True. But still *way* better than the current default of 64K. Thanks for the heads up! Regards, Wolfram --envbJBWh7q8WU6mo Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAlubuRIACgkQFA3kzBSg KbYDVg//bh36euxWfK0dddVBPVqm1s4zCPNzupGqOMeJXeOdE6jAkuHfePRjta8x PMgoScr4JvODfNPvIF+wR2pfc7/7WYgMK3+L3fwCaeNMyRxTFNDEvE/E0IkN+OXr oCBEuDRnPpeAXVNnvpKqBGwlmKC8o8PVoloGfjDBgbNz+LFJPyaJFnkVrZv3tdJp /nbJnVJ6Dxs7GmhcJNH9ZSEFGZuYrKqJjHf3WYR96Ef4bsjSNxEkmCxunWhZjPvR 8moF2UWpRPwMBYD7LEAoHdHL2c+phiB2v5bcKP6g0MnD1eAcdJ52GEKtBM+trzsT Qg19sOdYaQ6J8T8oVe40gJywUtbZ6sTmygKy3a1JNmPL+6hE5WULekMTVDo9Ipo2 mWuWCNh99IOY6kYNZMg6h4LXeLaB1NS46nLsaDOJ4evWK+E4pc8/7ATOBX57/KfE PMWpt7Te7WbE46pXRC2QoqMOg93Vhh77J9iA3uh/FlciGKoLqZjPBhWi5NSeylqD PyLxiZnPVrRYzdqMLXhbupz/PkjiuuGFrcjwG5+8KbXZFVIaNCFSlW1A4+U/Y65h Tr2b558f+JWMIzkABQyKu43/b/YtmZKfn49dMd+kEfcGkGERDxt/tJXi7LM3npI+ cBLoN3LoHzQIeXmHTZqIuRqh1grdOyUqb751g92oOvByd/nNnkE= =Wmfh -----END PGP SIGNATURE----- --envbJBWh7q8WU6mo--