From: Mark Brown <broonie@kernel.org>
To: Vignesh R <vigneshr@ti.com>
Cc: Tony Lindgren <tony@atomide.com>,
Michal Suchanek <hramrach@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-mtd@lists.infradead.org, linux-spi@vger.kernel.org
Subject: Re: [PATCH v2 1/5] spi: introduce mmap read support for spi flash devices
Date: Wed, 4 Nov 2015 14:39:15 +0000 [thread overview]
Message-ID: <20151104143915.GI1717@sirena.org.uk> (raw)
In-Reply-To: <1446545174-14193-2-git-send-email-vigneshr@ti.com>
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On Tue, Nov 03, 2015 at 03:36:10PM +0530, Vignesh R wrote:
> + }
> + mutex_lock(&master->mmap_lock_mutex);
> + ret = master->spi_mtd_mmap_read(spi, from, len, retlen, buf,
> + read_opcode, addr_width,
> + dummy_bytes);
> + mutex_unlock(&master->mmap_lock_mutex);
> + if (master->auto_runtime_pm)
> + pm_runtime_put(master->dev.parent);
It's a bit worrying that this doesn't sync with the message queue except
via the mutex: this means that we might be out of order with respect to
any asynchronous transfers that are happening on the device. I'm not
sure that this is a practical problem, though there is some risk of
unfair scheduling that would have to be under extreme load and it might
make sense to prioritise reads anyway.
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From: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Vignesh R <vigneshr-l0cyMroinI0@public.gmane.org>
Cc: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>,
Michal Suchanek
<hramrach-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v2 1/5] spi: introduce mmap read support for spi flash devices
Date: Wed, 4 Nov 2015 14:39:15 +0000 [thread overview]
Message-ID: <20151104143915.GI1717@sirena.org.uk> (raw)
In-Reply-To: <1446545174-14193-2-git-send-email-vigneshr-l0cyMroinI0@public.gmane.org>
[-- Attachment #1: Type: text/plain, Size: 741 bytes --]
On Tue, Nov 03, 2015 at 03:36:10PM +0530, Vignesh R wrote:
> + }
> + mutex_lock(&master->mmap_lock_mutex);
> + ret = master->spi_mtd_mmap_read(spi, from, len, retlen, buf,
> + read_opcode, addr_width,
> + dummy_bytes);
> + mutex_unlock(&master->mmap_lock_mutex);
> + if (master->auto_runtime_pm)
> + pm_runtime_put(master->dev.parent);
It's a bit worrying that this doesn't sync with the message queue except
via the mutex: this means that we might be out of order with respect to
any asynchronous transfers that are happening on the device. I'm not
sure that this is a practical problem, though there is some risk of
unfair scheduling that would have to be under extreme load and it might
make sense to prioritise reads anyway.
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From: broonie@kernel.org (Mark Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 1/5] spi: introduce mmap read support for spi flash devices
Date: Wed, 4 Nov 2015 14:39:15 +0000 [thread overview]
Message-ID: <20151104143915.GI1717@sirena.org.uk> (raw)
In-Reply-To: <1446545174-14193-2-git-send-email-vigneshr@ti.com>
On Tue, Nov 03, 2015 at 03:36:10PM +0530, Vignesh R wrote:
> + }
> + mutex_lock(&master->mmap_lock_mutex);
> + ret = master->spi_mtd_mmap_read(spi, from, len, retlen, buf,
> + read_opcode, addr_width,
> + dummy_bytes);
> + mutex_unlock(&master->mmap_lock_mutex);
> + if (master->auto_runtime_pm)
> + pm_runtime_put(master->dev.parent);
It's a bit worrying that this doesn't sync with the message queue except
via the mutex: this means that we might be out of order with respect to
any asynchronous transfers that are happening on the device. I'm not
sure that this is a practical problem, though there is some risk of
unfair scheduling that would have to be under extreme load and it might
make sense to prioritise reads anyway.
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next prev parent reply other threads:[~2015-11-04 14:40 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-03 10:06 [PATCH v2 0/5] Add memory mapped read support for ti-qspi Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` [PATCH v2 1/5] spi: introduce mmap read support for spi flash devices Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 11:19 ` Michal Suchanek
2015-11-03 11:19 ` Michal Suchanek
2015-11-03 11:19 ` Michal Suchanek
2015-11-04 4:48 ` Vignesh R
2015-11-04 4:48 ` Vignesh R
2015-11-04 4:48 ` Vignesh R
2015-11-04 4:48 ` Vignesh R
2015-11-04 4:48 ` Vignesh R
2015-11-04 14:39 ` Mark Brown [this message]
2015-11-04 14:39 ` Mark Brown
2015-11-04 14:39 ` Mark Brown
2015-11-05 12:29 ` Vignesh R
2015-11-05 12:29 ` Vignesh R
2015-11-05 12:29 ` Vignesh R
2015-11-05 15:29 ` Mark Brown
2015-11-05 15:29 ` Mark Brown
2015-11-03 10:06 ` [PATCH v2 2/5] spi: spi-ti-qspi: add mmap mode read support Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-04 14:41 ` Mark Brown
2015-11-04 14:41 ` Mark Brown
2015-11-04 14:41 ` Mark Brown
2015-11-05 6:16 ` Vignesh R
2015-11-05 6:16 ` Vignesh R
2015-11-05 6:16 ` Vignesh R
2015-11-05 6:16 ` Vignesh R
2015-11-03 10:06 ` [PATCH v2 3/5] mtd: devices: m25p80: add support for mmap read request Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` [PATCH v2 4/5] ARM: dts: DRA7: add entry for qspi mmap region Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-05 16:36 ` Rob Herring
2015-11-05 16:36 ` Rob Herring
2015-11-05 16:36 ` Rob Herring
2015-11-03 10:06 ` [PATCH v2 5/5] ARM: dts: AM4372: " Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-03 10:06 ` Vignesh R
2015-11-05 23:51 ` Rob Herring
2015-11-05 23:51 ` Rob Herring
2015-11-05 23:51 ` Rob Herring
2015-11-06 5:14 ` Felipe Balbi
2015-11-06 5:14 ` Felipe Balbi
2015-11-06 5:14 ` Felipe Balbi
2015-11-06 12:21 ` Vignesh R
2015-11-06 12:21 ` Vignesh R
2015-11-06 12:21 ` Vignesh R
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