From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyrille Pitchen Subject: Re: [PATCH linux-next v9 2/3] mfd: devicetree: add bindings for Atmel Flexcom Date: Wed, 9 Sep 2015 17:45:19 +0200 Message-ID: <55F0540F.6000102@atmel.com> References: <90fa2e0ded92567a29c996658153d833aaa5e411.1441118159.git.cyrille.pitchen@atmel.com> <55EF7209.8060407@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <55EF7209.8060407@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring , nicolas.ferre@atmel.com, boris.brezillon@free-electrons.com, alexandre.belloni@free-electrons.com, sameo@linux.intel.com, lee.jones@linaro.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org Hi Rob, Le 09/09/2015 01:40, Rob Herring a =E9crit : > On 09/01/2015 09:46 AM, Cyrille Pitchen wrote: >> This patch documents the DT bindings for the Atmel Flexcom which wil= l be >> introduced by sama5d2x SoCs. These bindings will be used by the actu= al >> Flexcom driver to be sent in another patch. >> >> Signed-off-by: Cyrille Pitchen >> Acked-by: Boris Brezillon >> Acked-by: Alexandre Belloni >=20 > A few comments, but in general looks fine. >=20 >> --- >> .../devicetree/bindings/mfd/atmel-flexcom.txt | 67 +++++++++++= +++++++++++ >> 1 file changed, 67 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/mfd/atmel-flex= com.txt >> >> diff --git a/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt= b/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt >> new file mode 100644 >> index 000000000000..fc3511e41542 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/mfd/atmel-flexcom.txt >> @@ -0,0 +1,67 @@ >> +* Device tree bindings for Atmel Flexcom (Flexible Serial Communica= tion Unit) >> + >> +The Atmel Flexcom is just a wrapper which embeds a SPI controller, = an I2C >> +controller and an USART. Only one function can be used at a time an= d is chosen >> +at boot time according to the device tree. >=20 > Doesn't the board design choose (unless pins go to a header)? >=20 The function may be chosen once for all by the board design but if we t= ake the sama5d2 xplained board as an example, most Flexcoms output their pins t= o headers. >> + >> +Required properties: >> +- compatible: Should be "atmel,sama5d2-flexcom" >> +- reg: Should be the offset/length value for Flexcom dedicated >> + I/O registers (without USART, TWI or SPI registers). >> +- clocks: Should be the Flexcom peripheral clock from PMC. >> +- #address-cells: Should be <1> >> +- #size-cells: Should be <1> >> +- ranges: Should be one range for the full I/O register region >> + (including USART, TWI and SPI registers). >> +- atmel,flexcom-mode: Should be one of the 3 following macros as de= fined in >> + include/dt-bindings/mfd/atmel-flexcom.h: >> + - ATMEL_FLEXCOM_MODE_USART for USART >> + - ATMEL_FLEXCOM_MODE_SPI for SPI >> + - ATMEL_FLEXCOM_MODE_TWI for I2C >> + >> +Required child: >> +a single child device of type matching the "atmel,flexcom-mode" pro= perty. >=20 > Okay, but why not allow all children and use "status"? >=20 That is exactly what was proposed in v6 of this series: allow more than= one child so possibly all children but only one "available" child (status =3D= =20 "okay"). The Flexocm driver still needs to find out the type of device of this available child to know which function is to be enabled (USART, I2C or = SPI). So the "compatible" attribute was parsed using strstr() to search on of= the patterns "usart", "spi" or "i2c". However the use of strstr() was discussed to know whether the driver sh= ould looks for a partial or an exact match of the "compatible" string. An exact match would require to keep the Flexcom driver synchonized wit= h the 3 other drivers every time one of them introduces a new compatibility s= tring, which whould have made every driver more difficult to maintain by creat= ing a useless dependency. So this implementation relying on the "compatible" attribute was abando= ned. To sum up, no other reliable (and simple) means to guess/extact the dev= ice type from its DT node was found so we got back to the "atmel,flexcom-mo= de" property. >> + >> +The reg property of this child should be: >> +- <0x200 0x200> for USART >> +- <0x400 0x200> for SPI >> +- <0x600 0x200> for I2C >> + >> +The phandle provided by the clocks property of the child is the sam= e as one for >> +the Flexcom parent. >> + >> +Other properties remain unchanged. See documentation of the respect= ive device: >> +- ../serial/atmel-usart.txt >> +- ../spi/spi_atmel.txt >> +- ../i2c/i2c-at91.txt >> + >> +Example: >> + >> +flexcom@f8034000 { >> + compatible =3D "atmel,sama5d2-flexcom"; >> + reg =3D <0xf8034000 0x200>; >> + clocks =3D <&flx0_clk>; >> + #address-cells =3D <1>; >> + #size-cells =3D <1>; >> + ranges =3D <0x0 0xf8034000 0x800>; >> + atmel,flexcom-mode =3D ; >> + >> + spi@400 { >> + compatible =3D "atmel,at91rm9200-spi"; >> + reg =3D <0x400 0x200>; >> + interrupts =3D <19 IRQ_TYPE_LEVEL_HIGH 7>; >> + pinctrl-names =3D "default"; >> + pinctrl-0 =3D <&pinctrl_flx0_default>; >> + #address-cells =3D <1>; >> + #size-cells =3D <0>; >> + clocks =3D <&flx0_clk>; >> + clock-names =3D "spi_clk"; >> + atmel,fifo-size =3D <32>; >> + >> + mtd_dataflash@0 { >> + compatible =3D "atmel,at25f512b"; >> + reg =3D <0>; >> + spi-max-frequency =3D <20000000>; >> + }; >> + }; >> +}; >> >=20 Best Regards, Cyrille