From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 10/14] mmc: mmci: Cache MMCICLOCK and MMCIPOWER register
Date: Sun, 8 Jan 2012 10:25:33 +0000 [thread overview]
Message-ID: <20120108102533.GA21765@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1323106560-5218-11-git-send-email-ulf.hansson@stericsson.com>
On Mon, Dec 05, 2011 at 06:35:56PM +0100, Ulf Hansson wrote:
> Instead of reading a register value everytime we need to
> apply a new value for it, maintain a cached copy for it.
> This also means we are able to skip writes that are not
> needed.
I'm not sure this is a good idea. The ARM Primecells require a certain
number of bus clocks and MCLK periods between writes to both these
registers, and reading them back helps to ensure that we conform to
that requirement. Maintaining a cached copy of them allows faster
writes to these registers which could cause that requirement to be
violated.
What you could do is read the register, modify, and check whether the
modification has had any effect before writing it back. That will
allow unnecessary writes to still be skipped.
next prev parent reply other threads:[~2012-01-08 10:25 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-05 17:35 [PATCH 00/14] mmc: mmci: Improved PM support, cleanup and bugfixes Ulf Hansson
2011-12-05 17:35 ` [PATCH 01/14] mmc: mmci: Support MMC_PM_KEEP_POWER Ulf Hansson
2011-12-05 17:35 ` [PATCH 02/14] mmc: mmci: Fixup handling of MCI_STARTBITERR Ulf Hansson
2011-12-18 23:15 ` Russell King - ARM Linux
2011-12-19 8:59 ` Ulf Hansson
2011-12-05 17:35 ` [PATCH 03/14] mmc: mmci: Increase max_segs from 16 to 128 Ulf Hansson
2011-12-05 17:35 ` [PATCH 04/14] mmc: mmci: Do not release spinlock in request_end Ulf Hansson
2011-12-05 17:35 ` [PATCH 05/14] mmc: mmci: Put power register deviations in variant data Ulf Hansson
2011-12-05 17:35 ` [PATCH 06/14] mmc: mmci: Provide option to configure bus signal direction Ulf Hansson
2011-12-05 17:35 ` [PATCH 07/14] mmc: mmci: Change vdd_handler to a generic ios_handler Ulf Hansson
2011-12-05 17:35 ` [PATCH 08/14] mmc: mmci: Fixup error handling for dma Ulf Hansson
2011-12-18 23:16 ` Russell King - ARM Linux
2011-12-19 8:59 ` Ulf Hansson
2011-12-05 17:35 ` [PATCH 09/14] mmc: mmci: Change from using legacy suspend Ulf Hansson
2011-12-05 17:35 ` [PATCH 10/14] mmc: mmci: Cache MMCICLOCK and MMCIPOWER register Ulf Hansson
2012-01-08 10:25 ` Russell King - ARM Linux [this message]
2012-01-09 11:46 ` Ulf Hansson
2012-01-09 15:12 ` Ulf Hansson
2011-12-05 17:35 ` [PATCH 11/14] mmc: mmci: Fixup use of runtime PM and use autosuspend Ulf Hansson
2011-12-05 17:35 ` [PATCH 12/14] mmc: mmci: Decrease current consumption in suspend Ulf Hansson
2012-01-08 10:38 ` Russell King - ARM Linux
2012-01-09 14:12 ` Ulf Hansson
2011-12-05 17:35 ` [PATCH 13/14] mmc: mmci: Implement PM runtime callbacks to save power Ulf Hansson
2011-12-05 17:36 ` [PATCH 14/14] mmc: mmci: Use ios_handler " Ulf Hansson
2011-12-07 12:06 ` [PATCH 00/14] mmc: mmci: Improved PM support, cleanup and bugfixes Linus Walleij
2011-12-13 16:17 ` Ulf Hansson
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