From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomi Valkeinen Date: Thu, 09 Jan 2014 08:21:46 +0000 Subject: Re: [PATCH 1/2] ARM: omapfb: add coherent dma memory support Message-Id: <52CE5C1A.3070603@ti.com> MIME-Version: 1 Content-Type: multipart/mixed; boundary="oGPgmg3OQno4QS60kBCq6gCNbMTPg8BfL" List-Id: References: <1388409550-10720-1-git-send-email-tomi.valkeinen@ti.com> <1388409550-10720-2-git-send-email-tomi.valkeinen@ti.com> <20140107235951.GH5074@atomide.com> <52CD5D13.9090806@ti.com> <79CD15C6BA57404B839C016229A409A83EDB11F5@DBDE04.ent.ti.com> In-Reply-To: <79CD15C6BA57404B839C016229A409A83EDB11F5@DBDE04.ent.ti.com> To: linux-arm-kernel@lists.infradead.org --oGPgmg3OQno4QS60kBCq6gCNbMTPg8BfL Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2014-01-09 07:06, Hiremath, Vaibhav wrote: > I am seeing underflow issue on AM43x device if I use omapfb_vram argume= nt. > Did you see this on OMAP? >=20 > I am using "omapfb_vram=3D10M@0xA0000000", and I believe it is correct = way of usage. Hmm ok... The AM4x seems to have issues anyway, as we're seeing underflows easily in other situations also. Well, there's a small difference in the allocation. The normal dma alloc uses dma_alloc_attrs() and passes DMA_ATTR_WRITE_COMBINE as a flag, whereas allocating from the absolute address just uses the piece of memory. I couldn't find how to set write-combine for the abs memory area.= Then again, that's for CPU caching, so I don't see why it would affect DSS as such (but that's still something we should measure, cpu read/write perf for normal and abs allocation). The only thought I have is that somehow the reserved memory area is missing some configuration that is done for the rest of the memory. But that's purely a guess, this is totally out of my area of expertise... Vaibhav, just to be sure, can you run both with normal dma_alloc and with the reserve, and verify that the dispc register dumps are the same? I don't see how they could be different, but just to be sure. Tomi --oGPgmg3OQno4QS60kBCq6gCNbMTPg8BfL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBAgAGBQJSzlweAAoJEPo9qoy8lh71j1YQAJ71toua5iWbpBW3l8SD/Xwu Q0UX6cVcPpOCihYtVUWSWKQRCiSZ+gTMtrFumQNxvxDRt9Gywj4yTuOJBCuko9G9 hPeFlSFB3YusGDxcsSTaimfKQOmRwCbMM8SYk2ximM2lcuUg3CsQ2oyfMPIpdKct unQ/2JVgO2o1axKNKNIwGdns8t3UqkBGgWcVyxgdliPBGAzqp8sUeX/5hq2Vx3/s OLobVu+G3i2BaEV/3S4UNYVDA9g/HTXACtej8bW2z06YmqHVUU0H9g1Setiyo1TX eH+1TDECnHJnAYNM2AtkJIN6zgC3UXyzrzcAuL8T/uIWoLvy/qMQAJbe5ijIcXKj n7I5c1rtV7VRxSaUcdQ3UER4NSjb5AEw7xgCE7BJIWanxavJMpv1+VyorZdVIdNt ymgwBT1Y2jc3DYqt/19o3cRCo0tOjG6w8esDvXBc7qPo9s9ao9qLeSIzPWPikA7o n6V0V9Ii18HdOsg9iJmd//G2Boky52b+pffhcKp0frKqZ2F8fMvnI409M1Vmcslj k0DRobamlya9PFa0ZNZpo2zfFbupt4w7zf0gb6GgWn26oYARQOm8abmPmS1manN3 8wpS6NIqhoIm7L3frFlFF9b+8ZjcvJns5EvgDX3zOf9ZsqoS0ClVoBNtq180CmU4 gM644Q+GPMWrq1MMQYVe =u3mX -----END PGP SIGNATURE----- --oGPgmg3OQno4QS60kBCq6gCNbMTPg8BfL--