From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [PATCH 1/3] spi/qspi: Add memory mapped read support. Date: Wed, 9 Oct 2013 20:36:47 +0100 Message-ID: <20131009193647.GA21581@sirena.org.uk> References: <1381332284-21822-1-git-send-email-sourav.poddar@ti.com> <1381332284-21822-2-git-send-email-sourav.poddar@ti.com> <20131009160759.GQ21581@sirena.org.uk> <52558A49.5090904@ti.com> <20131009174027.GS21581@sirena.org.uk> <87hacq1d5k.fsf@dell.be.48ers.dk> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============7751547304807162355==" Cc: balbi@ti.com, linux-mtd@lists.infradead.org, spi-devel-general@lists.sourceforge.net, Sourav Poddar , computersforpeace@gmail.com, dwmw2@infradead.org To: Peter Korsgaard Return-path: In-Reply-To: <87hacq1d5k.fsf@dell.be.48ers.dk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-mtd" Errors-To: linux-mtd-bounces+gldm-linux-mtd-36=gmane.org@lists.infradead.org List-Id: linux-spi.vger.kernel.org --===============7751547304807162355== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="/c0JJ5TGZ+xtmyhA" Content-Disposition: inline --/c0JJ5TGZ+xtmyhA Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Oct 09, 2013 at 09:01:59PM +0200, Peter Korsgaard wrote: > Indeed. I can see how such a feature could be useful in E.G. a lowlevel > bootloader (because of simplicity), but am less convinced about it in > Linux where we could conceivable do something else useful while waiting > on the spi controller. > But if there's number to prove otherwise.. I can see it being useful if there's a DMA controller that can do the transfer as a memory to memory DMA - the hardware can probably issue flash read commands a bit faster than the AP can so you should be able to get closer to saturating the bus. The patches didn't try to do that or make it possible for something further up the stack to do it and the differences should end up being fairly small with optimisations like those in the pxa2xx or pl022 drivers (which I'm currently working on pulling out into the framework). --/c0JJ5TGZ+xtmyhA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSVbBMAAoJELSic+t+oim99HsQAI6w5/W7EjDQTZQ6+g2KadMP Bojzk7yjH07ZRpfONeMgzzWPTdVHOHRK6i/YWVib+8IjncMNXBPoYVGMrBqau73T Bt/os5LSVqnL7ZQ1MSjYe3i/4IFoSXmACa1RQYs3ULjxMmXMcOteCwb4P4I/Euy6 Fnn1QCaFzmAHGZ9XNuU6Mb/05doK6mCGu+89vo6EkQuhjrtJ3ZAhBfeNE/zEY6eI JEiP/DoLmpVe8IwXoTb+NfO2oLGrISG3pX9YHGIFADdINA9uFz+0xSMt8UuoiS7P iZ2gpPClKAj6zobtgGbrqn4SoC2npmwUsudHY05gP1H9h7/4diKFORcAZaiCosoK AzNsnR7i8bjcYYBuc+k7CxSvqkXUTdfAWnSwnyfHgsPymc0A+FNyueDNWfNASJas OUOyQZIafRYE7ypmdFe0Q0c1B6COaKNU2Va1ejTxKRBfUvxoUXbNgbFb2jMHRdm8 AIjNrjkaukJSi6xHickznAbm5hXeyvoXuu6lcc5xlQWvum6EtiKmrKWE1e/R+ocK 0Yer+bNlT5dVqApU4x9FBsLkrqsMWFJBsiWnESLb5tqDyCi9oejIgGmpZz+Zx7gl TuIKYTtWPUOuax6FGqLpYPuAEfeP/FrUDbhM03m1kqaL4cuUGaJFTbHSkUyw9aQa 8o+9QKLwK2NA0FUR6vgy =2Ny9 -----END PGP SIGNATURE----- --/c0JJ5TGZ+xtmyhA-- --===============7751547304807162355== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/ --===============7751547304807162355==-- From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [2001:41c8:1:5384::2] (helo=cassiel.sirena.org.uk) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1VTzZu-0006mA-FJ for linux-mtd@lists.infradead.org; Wed, 09 Oct 2013 19:37:50 +0000 Date: Wed, 9 Oct 2013 20:36:47 +0100 From: Mark Brown To: Peter Korsgaard Message-ID: <20131009193647.GA21581@sirena.org.uk> References: <1381332284-21822-1-git-send-email-sourav.poddar@ti.com> <1381332284-21822-2-git-send-email-sourav.poddar@ti.com> <20131009160759.GQ21581@sirena.org.uk> <52558A49.5090904@ti.com> <20131009174027.GS21581@sirena.org.uk> <87hacq1d5k.fsf@dell.be.48ers.dk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="/c0JJ5TGZ+xtmyhA" Content-Disposition: inline In-Reply-To: <87hacq1d5k.fsf@dell.be.48ers.dk> Subject: Re: [PATCH 1/3] spi/qspi: Add memory mapped read support. Cc: balbi@ti.com, linux-mtd@lists.infradead.org, spi-devel-general@lists.sourceforge.net, Sourav Poddar , computersforpeace@gmail.com, dwmw2@infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --/c0JJ5TGZ+xtmyhA Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Oct 09, 2013 at 09:01:59PM +0200, Peter Korsgaard wrote: > Indeed. I can see how such a feature could be useful in E.G. a lowlevel > bootloader (because of simplicity), but am less convinced about it in > Linux where we could conceivable do something else useful while waiting > on the spi controller. > But if there's number to prove otherwise.. I can see it being useful if there's a DMA controller that can do the transfer as a memory to memory DMA - the hardware can probably issue flash read commands a bit faster than the AP can so you should be able to get closer to saturating the bus. The patches didn't try to do that or make it possible for something further up the stack to do it and the differences should end up being fairly small with optimisations like those in the pxa2xx or pl022 drivers (which I'm currently working on pulling out into the framework). --/c0JJ5TGZ+xtmyhA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSVbBMAAoJELSic+t+oim99HsQAI6w5/W7EjDQTZQ6+g2KadMP Bojzk7yjH07ZRpfONeMgzzWPTdVHOHRK6i/YWVib+8IjncMNXBPoYVGMrBqau73T Bt/os5LSVqnL7ZQ1MSjYe3i/4IFoSXmACa1RQYs3ULjxMmXMcOteCwb4P4I/Euy6 Fnn1QCaFzmAHGZ9XNuU6Mb/05doK6mCGu+89vo6EkQuhjrtJ3ZAhBfeNE/zEY6eI JEiP/DoLmpVe8IwXoTb+NfO2oLGrISG3pX9YHGIFADdINA9uFz+0xSMt8UuoiS7P iZ2gpPClKAj6zobtgGbrqn4SoC2npmwUsudHY05gP1H9h7/4diKFORcAZaiCosoK AzNsnR7i8bjcYYBuc+k7CxSvqkXUTdfAWnSwnyfHgsPymc0A+FNyueDNWfNASJas OUOyQZIafRYE7ypmdFe0Q0c1B6COaKNU2Va1ejTxKRBfUvxoUXbNgbFb2jMHRdm8 AIjNrjkaukJSi6xHickznAbm5hXeyvoXuu6lcc5xlQWvum6EtiKmrKWE1e/R+ocK 0Yer+bNlT5dVqApU4x9FBsLkrqsMWFJBsiWnESLb5tqDyCi9oejIgGmpZz+Zx7gl TuIKYTtWPUOuax6FGqLpYPuAEfeP/FrUDbhM03m1kqaL4cuUGaJFTbHSkUyw9aQa 8o+9QKLwK2NA0FUR6vgy =2Ny9 -----END PGP SIGNATURE----- --/c0JJ5TGZ+xtmyhA--