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From: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>
To: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH] i2c: mxs: remove broken PIOQUEUE support
Date: Thu, 1 Nov 2012 15:28:17 +0100	[thread overview]
Message-ID: <201211011528.17596.marex@denx.de> (raw)
In-Reply-To: <1351771003-6071-1-git-send-email-w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>

Dear Wolfram Sang,

> This I2C master can do DMA and PIOQUEUE (PIO with FIFO). Originally,
> only PIOQEUE

PIOQUEUE ;-)

> was supported, then DMA support was added. The original
> intention was to keep PIOQUEUE since it has less overhead what is nice
> for small transfers. However, runtime switching between PIOQEUE and DMA
> depending on the transfer size never worked despite a lot of trying.
> Since PIOQUEUE mode itself was flaky (polling at places where interrupts
> failed to work) and the implementation also imposed a size limit for
> transfers, it is best to remove the support altogether which makes the
> driver a lot cleaner and more robust. If somebody really wants less
> overhead, plain PIO mode could still be implemented with the addidtional
> advantage that this mode is also available on MX23, too.

Yes, looks to be the way to go.

Reviewed-by: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>

Thanks

[...]

Best regards,
Marek Vasut

WARNING: multiple messages have this Message-ID (diff)
From: marex@denx.de (Marek Vasut)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] i2c: mxs: remove broken PIOQUEUE support
Date: Thu, 1 Nov 2012 15:28:17 +0100	[thread overview]
Message-ID: <201211011528.17596.marex@denx.de> (raw)
In-Reply-To: <1351771003-6071-1-git-send-email-w.sang@pengutronix.de>

Dear Wolfram Sang,

> This I2C master can do DMA and PIOQUEUE (PIO with FIFO). Originally,
> only PIOQEUE

PIOQUEUE ;-)

> was supported, then DMA support was added. The original
> intention was to keep PIOQUEUE since it has less overhead what is nice
> for small transfers. However, runtime switching between PIOQEUE and DMA
> depending on the transfer size never worked despite a lot of trying.
> Since PIOQUEUE mode itself was flaky (polling at places where interrupts
> failed to work) and the implementation also imposed a size limit for
> transfers, it is best to remove the support altogether which makes the
> driver a lot cleaner and more robust. If somebody really wants less
> overhead, plain PIO mode could still be implemented with the addidtional
> advantage that this mode is also available on MX23, too.

Yes, looks to be the way to go.

Reviewed-by: Marek Vasut <marex@denx.de>

Thanks

[...]

Best regards,
Marek Vasut

  parent reply	other threads:[~2012-11-01 14:28 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-01 11:56 [PATCH] i2c: mxs: remove broken PIOQUEUE support Wolfram Sang
2012-11-01 11:56 ` Wolfram Sang
     [not found] ` <1351771003-6071-1-git-send-email-w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-11-01 14:28   ` Marek Vasut [this message]
2012-11-01 14:28     ` Marek Vasut
     [not found]     ` <201211011528.17596.marex-ynQEQJNshbs@public.gmane.org>
2012-11-01 16:08       ` Wolfram Sang
2012-11-01 16:08         ` Wolfram Sang
     [not found]         ` <20121101160828.GA18425-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-11-01 16:12           ` Marek Vasut
2012-11-01 16:12             ` Marek Vasut

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