From: "Gupta, Pekon" <pekon@ti.com>
To: Trent Piepho <tpiepho@gmail.com>
Cc: Peter Korsgaard <peter@korsgaard.com>,
"Balbi, Felipe" <balbi@ti.com>, Mark Brown <broonie@kernel.org>,
"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
"spi-devel-general@lists.sourceforge.net"
<spi-devel-general@lists.sourceforge.net>,
"Poddar, Sourav" <sourav.poddar@ti.com>,
Brian Norris <computersforpeace@gmail.com>,
David Woodhouse <dwmw2@infradead.org>
Subject: RE: [PATCH 1/3] spi/qspi: Add memory mapped read support.
Date: Tue, 15 Oct 2013 18:33:23 +0000 [thread overview]
Message-ID: <20980858CB6D3A4BAE95CA194937D5E73EA23640@DBDE04.ent.ti.com> (raw)
In-Reply-To: <CA+7tXigv1Q3BPE3uhzdJpx3DsqUpxzrBUaPfWR-i15PsVtMWsQ@mail.gmail.com>
> From: Trent Piepho
> Are there any numbers to show if memory mapped read support is a
> benefit in Linux? There is some question as to whether it's useful at
> all or not.
>
> If it is, I think low latency for small reads is probably one of the
> only advantages. To do that, you aren't going to want to deal with
> device PM for every single read. It would make more sense to turn the
> hardware on when the MTD device is opened and leave it on until
> closed.
>
+1
Therefore early suggestions were to make 'MM_MODE' as default
(if device enables it via DT). This means:
(1) switch to 'SPI_MODE' _only_ when required for commands like
mtd_erase, etc. and switch back to 'MM_MODE' when done.
(2) And keep your controller clocks on.
This would ensure that you do minimum config-switching when using
MM_MODE. And would thus achieve low latency, and no driver intervention.
Yes, real thruput numbers would help clear the picture here ..
with regards, pekon
______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
WARNING: multiple messages have this Message-ID (diff)
From: "Gupta, Pekon" <pekon@ti.com>
To: Trent Piepho <tpiepho@gmail.com>
Cc: Peter Korsgaard <peter@korsgaard.com>,
"Balbi, Felipe" <balbi@ti.com>, Mark Brown <broonie@kernel.org>,
"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
"spi-devel-general@lists.sourceforge.net"
<spi-devel-general@lists.sourceforge.net>,
"Poddar, Sourav" <sourav.poddar@ti.com>,
Brian Norris <computersforpeace@gmail.com>,
David Woodhouse <dwmw2@infradead.org>
Subject: RE: [PATCH 1/3] spi/qspi: Add memory mapped read support.
Date: Tue, 15 Oct 2013 18:33:23 +0000 [thread overview]
Message-ID: <20980858CB6D3A4BAE95CA194937D5E73EA23640@DBDE04.ent.ti.com> (raw)
In-Reply-To: <CA+7tXigv1Q3BPE3uhzdJpx3DsqUpxzrBUaPfWR-i15PsVtMWsQ@mail.gmail.com>
> From: Trent Piepho
> Are there any numbers to show if memory mapped read support is a
> benefit in Linux? There is some question as to whether it's useful at
> all or not.
>
> If it is, I think low latency for small reads is probably one of the
> only advantages. To do that, you aren't going to want to deal with
> device PM for every single read. It would make more sense to turn the
> hardware on when the MTD device is opened and leave it on until
> closed.
>
+1
Therefore early suggestions were to make 'MM_MODE' as default
(if device enables it via DT). This means:
(1) switch to 'SPI_MODE' _only_ when required for commands like
mtd_erase, etc. and switch back to 'MM_MODE' when done.
(2) And keep your controller clocks on.
This would ensure that you do minimum config-switching when using
MM_MODE. And would thus achieve low latency, and no driver intervention.
Yes, real thruput numbers would help clear the picture here ..
with regards, pekon
next prev parent reply other threads:[~2013-10-15 18:33 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-09 15:24 [PATCH 0/3]Add quad/memory mapped support for SPI flash Sourav Poddar
2013-10-09 15:24 ` Sourav Poddar
2013-10-09 15:24 ` [PATCH 1/3] spi/qspi: Add memory mapped read support Sourav Poddar
2013-10-09 15:24 ` Sourav Poddar
2013-10-09 16:07 ` Mark Brown
2013-10-09 16:07 ` Mark Brown
[not found] ` <20131009160759.GQ21581-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2013-10-09 16:54 ` Sourav Poddar
2013-10-09 16:54 ` Sourav Poddar
2013-10-09 17:40 ` Mark Brown
2013-10-09 17:40 ` Mark Brown
2013-10-09 18:15 ` Sourav Poddar
2013-10-09 18:15 ` Sourav Poddar
2013-10-09 18:41 ` Mark Brown
2013-10-09 18:41 ` Mark Brown
[not found] ` <20131009174027.GS21581-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2013-10-09 19:01 ` Peter Korsgaard
2013-10-09 19:01 ` Peter Korsgaard
2013-10-09 19:36 ` Mark Brown
2013-10-09 19:36 ` Mark Brown
[not found] ` <87hacq1d5k.fsf-D6SC8u56vOOJDPpyT6T3/w@public.gmane.org>
2013-10-10 2:27 ` Trent Piepho
2013-10-10 2:27 ` Trent Piepho
2013-10-10 8:52 ` Sourav Poddar
2013-10-10 8:52 ` Sourav Poddar
2013-10-10 10:14 ` Mark Brown
2013-10-10 10:14 ` Mark Brown
2013-10-10 10:17 ` Sourav Poddar
2013-10-10 10:17 ` Sourav Poddar
2013-10-10 11:08 ` Sourav Poddar
2013-10-10 11:08 ` Sourav Poddar
2013-10-11 10:08 ` Mark Brown
2013-10-11 10:08 ` Mark Brown
2013-10-15 6:06 ` Sourav Poddar
2013-10-15 6:06 ` Sourav Poddar
2013-10-15 11:16 ` Mark Brown
2013-10-15 11:16 ` Mark Brown
2013-10-15 11:49 ` Sourav Poddar
2013-10-15 11:49 ` Sourav Poddar
2013-10-15 12:46 ` Mark Brown
2013-10-15 12:46 ` Mark Brown
[not found] ` <20131015124656.GM2443-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2013-10-15 13:23 ` Sourav Poddar
2013-10-15 13:23 ` Sourav Poddar
2013-10-15 15:53 ` Mark Brown
2013-10-15 15:53 ` Mark Brown
[not found] ` <525D41E2.30206-l0cyMroinI0@public.gmane.org>
2013-10-15 15:33 ` Gupta, Pekon
2013-10-15 15:33 ` Gupta, Pekon
2013-10-15 16:01 ` Mark Brown
2013-10-15 16:01 ` Mark Brown
2013-10-15 16:54 ` Gupta, Pekon
2013-10-15 16:54 ` Gupta, Pekon
2013-10-15 18:01 ` Brian Norris
2013-10-15 18:01 ` Brian Norris
2013-10-15 18:10 ` Sourav Poddar
2013-10-15 18:10 ` Sourav Poddar
[not found] ` <20131015180142.GS23337-bU/DPfM3abD4WzifrMjOTkcViWtcw2C0@public.gmane.org>
2013-10-15 18:13 ` Trent Piepho
2013-10-15 18:13 ` Trent Piepho
2013-10-15 18:33 ` Gupta, Pekon [this message]
2013-10-15 18:33 ` Gupta, Pekon
2013-10-15 20:52 ` Mark Brown
2013-10-15 20:52 ` Mark Brown
[not found] ` <20131015205254.GX2443-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2013-10-15 21:03 ` Trent Piepho
2013-10-15 21:03 ` Trent Piepho
2013-10-15 22:10 ` Mark Brown
2013-10-15 22:10 ` Mark Brown
[not found] ` <20980858CB6D3A4BAE95CA194937D5E73EA23640-yXqyApvAXouIQmiDNMet8wC/G2K4zDHf@public.gmane.org>
2013-10-17 12:24 ` Sourav Poddar
2013-10-17 12:24 ` Sourav Poddar
2013-10-17 12:38 ` Mark Brown
2013-10-17 12:38 ` Mark Brown
2013-10-17 13:03 ` Gupta, Pekon
2013-10-17 13:03 ` Gupta, Pekon
2013-10-17 23:42 ` Mark Brown
2013-10-18 4:06 ` Sourav Poddar
2013-10-18 5:56 ` Trent Piepho
2013-10-18 6:10 ` Sourav Poddar
2013-10-18 7:27 ` Sourav Poddar
2013-10-18 10:31 ` Mark Brown
2013-10-18 11:48 ` Sourav Poddar
2013-10-18 13:08 ` Mark Brown
2013-10-18 14:47 ` Sourav Poddar
2013-10-15 20:59 ` Mark Brown
2013-10-15 20:59 ` Mark Brown
[not found] ` <52566ACC.1080100-l0cyMroinI0@public.gmane.org>
2013-10-11 9:30 ` Gupta, Pekon
2013-10-11 9:30 ` Gupta, Pekon
2013-10-10 10:10 ` Mark Brown
2013-10-10 10:10 ` Mark Brown
[not found] ` <20131010101052.GF21581-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2013-10-10 23:53 ` Trent Piepho
2013-10-11 9:59 ` Mark Brown
2013-10-11 9:59 ` Mark Brown
2013-10-09 15:24 ` [PATCHv3 2/3] drivers: mtd: devices: Add quad " Sourav Poddar
2013-10-09 15:24 ` Sourav Poddar
[not found] ` <1381332284-21822-3-git-send-email-sourav.poddar-l0cyMroinI0@public.gmane.org>
2013-10-09 18:15 ` Jagan Teki
2013-10-09 18:15 ` Jagan Teki
[not found] ` <CAD6G_RShZMkSpVzvXWEE0+sDX=pcnf7ndChndgDG5_T4EVL2vQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-10-11 7:10 ` Gupta, Pekon
2013-10-11 7:10 ` Gupta, Pekon
2013-10-24 1:06 ` Brian Norris
2013-10-24 5:44 ` Sourav Poddar
2013-10-24 7:34 ` Brian Norris
2013-10-24 8:44 ` Sourav Poddar
2013-10-24 17:07 ` Brian Norris
2013-10-24 17:55 ` Sourav Poddar
2013-10-09 15:24 ` [RFC/PATCH 3/3] drivers: mtd: devices: Add memory mapped " Sourav Poddar
2013-10-09 15:24 ` Sourav Poddar
2013-10-09 15:45 ` Mark Brown
2013-10-09 15:45 ` Mark Brown
2013-10-24 0:22 ` [PATCH 0/3]Add quad/memory mapped support for SPI flash Brian Norris
2013-10-24 4:51 ` Sourav Poddar
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