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From: Brendan Higgins <brendanhiggins@google.com>
To: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, linux-aspeed@lists.ozlabs.org,
	Andrew Jeffery <andrew@aj.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	openbmc@lists.ozlabs.org, Rob Herring <robh+dt@kernel.org>,
	Joel Stanley <joel@jms.id.au>, Tao Ren <taoren@fb.com>,
	linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org
Subject: Re: [PATCH 1/5] dt-bindings: i2c: aspeed: add buffer and DMA mode transfer support
Date: Tue, 8 Oct 2019 11:12:13 -0700
Message-ID: <20191008181213.GB155928@google.com> (raw)
In-Reply-To: <20191007231313.4700-2-jae.hyun.yoo@linux.intel.com>

On Mon, Oct 07, 2019 at 04:13:09PM -0700, Jae Hyun Yoo wrote:
> Append bindings to support buffer mode and DMA mode transfer.
> 
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> ---
>  .../devicetree/bindings/i2c/i2c-aspeed.txt    | 67 +++++++++++++++++--
>  1 file changed, 60 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
> index 8fbd8633a387..e40dcc108307 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-aspeed.txt
> @@ -3,7 +3,10 @@ Device tree configuration for the I2C busses on the AST24XX and AST25XX SoCs.
>  Required Properties:
>  - #address-cells	: should be 1
>  - #size-cells		: should be 0
> -- reg			: address offset and range of bus
> +- reg			: Address offset and range of bus registers.
> +			  An additional SRAM buffer address offset and range is
> +			  optional in case of enabling I2C dedicated SRAM for
> +			  buffer mode transfer support.

Sorry, I am having trouble parsing this. This seems like the SRAM buffer
is global to all busses. Can you clarify? I expect I will probably have
some more questions elsewhere.

>  - compatible		: should be "aspeed,ast2400-i2c-bus"
>  			  or "aspeed,ast2500-i2c-bus"
>  - clocks		: root clock of bus, should reference the APB
> @@ -16,6 +19,18 @@ Optional Properties:
>  - bus-frequency	: frequency of the bus clock in Hz defaults to 100 kHz when not
>  		  specified
>  - multi-master	: states that there is another master active on this bus.
> +- aspeed,dma-buf-size	: size of DMA buffer (from 2 to 4095 in case of AST2500
> +			  or later versions).
> +			  Only AST2500 and later versions support DMA mode
> +			  under some limitations:
> +			  I2C is sharing the DMA H/W with UHCI host controller
> +			  and MCTP controller. Since those controllers operate
> +			  with DMA mode only, I2C has to use buffer mode or byte
> +			  mode instead if one of those controllers is enabled.
> +			  Also make sure that if SD/eMMC or Port80 snoop uses
> +			  DMA mode instead of PIO or FIFO respectively, I2C
> +			  can't use DMA mode. If both DMA and buffer modes are
> +			  enabled, DMA mode will be selected.

nit: I think it makes sense to break down the exceptions into a
bulleted list.

Cheers

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Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-07 23:13 [PATCH 0/5] i2c: aspeed: Add buffer and DMA modes support Jae Hyun Yoo
2019-10-07 23:13 ` [PATCH 1/5] dt-bindings: i2c: aspeed: add buffer and DMA mode transfer support Jae Hyun Yoo
2019-10-08 18:12   ` Brendan Higgins [this message]
2019-10-08 18:47     ` Jae Hyun Yoo
2019-10-07 23:13 ` [PATCH 2/5] ARM: dts: aspeed: add I2C buffer mode support Jae Hyun Yoo
2019-10-09 13:32   ` Cédric Le Goater
2019-10-07 23:13 ` [PATCH 3/5] i2c: aspeed: fix master pending state handling Jae Hyun Yoo
2019-10-08 20:31   ` Brendan Higgins
2019-10-08 21:13     ` Jae Hyun Yoo
2019-10-08 21:54       ` Brendan Higgins
2019-10-08 22:55         ` Jae Hyun Yoo
2019-10-10  5:28         ` Joel Stanley
2019-10-08 22:00   ` Tao Ren
2019-10-08 22:45     ` Jae Hyun Yoo
2019-10-08 23:15       ` Tao Ren
2019-10-08 23:28         ` Jae Hyun Yoo
2019-10-07 23:13 ` [PATCH 4/5] i2c: aspeed: add buffer mode transfer support Jae Hyun Yoo
2019-10-08 20:12   ` Brendan Higgins
2019-10-08 21:10     ` Jae Hyun Yoo
2019-10-08 23:15       ` Brendan Higgins
2019-10-09  0:08         ` Jae Hyun Yoo
2019-10-07 23:13 ` [PATCH 5/5] i2c: aspeed: add DMA " Jae Hyun Yoo

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