Hi Rob, On Wed, 18 Oct 2017 08:29:07 -0500 Rob Herring <robh@xxxxxxxxxx> wrote: > On Wed, Oct 18, 2017 at 1:25 AM, Miquel RAYNAL > <miquel.raynal@xxxxxxxxxxxxxxxxxx> wrote: > > Hi Rob, > > > > On Tue, 17 Oct 2017 17:00:22 -0500 > > Rob Herring <robh@xxxxxxxxxx> wrote: > > > >> On Fri, Oct 13, 2017 at 11:01:45AM +0200, Miquel Raynal wrote: > >> > Update the Device Tree binding documentation for the Marvell EBU > >> > UART, in order to allow describing the extended UART IP block, in > >> > addition to the already supported standard UART IP. This requires > >> > adding a new compatible string, the introduction of a clocks > >> > property, and extensions to the interrupts property. > >> > > >> > Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxxxxxxxxx> > >> > Reviewed-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxxxxxxxxx> > >> > --- > >> > .../devicetree/bindings/serial/mvebu-uart.txt | 49 > >> > +++++++++++++++++++--- 1 file changed, 44 insertions(+), 5 > >> > deletions(-) > >> > > >> > diff --git > >> > a/Documentation/devicetree/bindings/serial/mvebu-uart.txt > >> > b/Documentation/devicetree/bindings/serial/mvebu-uart.txt index > >> > d37fabe17bd1..3df3a3fab4bb 100644 --- > >> > a/Documentation/devicetree/bindings/serial/mvebu-uart.txt +++ > >> > b/Documentation/devicetree/bindings/serial/mvebu-uart.txt @@ > >> > -1,13 +1,52 @@ -* Marvell UART : Non standard UART used in some > >> > of Marvell EBU SoCs (e.g., Armada-3700) +* Marvell UART : Non > >> > standard UART used in some of Marvell EBU SoCs > >> > + e.g., Armada-3700. > >> > > >> > Required properties: > >> > -- compatible: "marvell,armada-3700-uart" > >> > +- compatible: > >> > + - "marvell,armada-3700-uart" for the standard variant of the > >> > UART > >> > + (32 bytes FIFO, no DMA, level interrupts, 8-bit access to > >> > the > >> > + FIFO, baudrate limited to 230400). > >> > + - "marvell,armada-3700-uart-ext" for the extended variant of > >> > the > >> > + UART (128 bytes FIFO, DMA, front interrupts, 8-bit or > >> > 32-bit > >> > + accesses to the FIFO, baudrate unlimited by the > >> > dividers). > >> > >> What do you call the next extended version? > >> marvell,armada-3700-uart-ext-ext? > > > > I don't know what you mean by "next extended version"? > > IP evolves on new chips with new features. Just trying to understand > how you are I think I misunderstood your initial question. Indeed you are right, I did not think about the naming of a potential next extended version of the extended IP, but I don't know how to rename it otherwise than "-ext" to best fit what the "new" IP does. > > >> This is different versions of UART on the same chip? > > > > Today in mainline there is support for the A3700 UART IP. > > This series add support for another IP, based on the A3700, but with > > extended features (explaining the -ext suffix). > > > > Can you precise what is bothering you? > > Is this different versions of UART IP on 1 chip or a new version of > the UART IP on a new SoC? The latter should be a new compatible with > the new SoC. The former case does happen some, but is not common. I'm > just trying to understand which applies here. Actually, both IP are available since the first version of the Armada 3700 SoCs. There is no other implementation of these IPs yet. I think we fall in the former case. > > > >> > - reg: offset and length of the register set for the device. > >> > -- interrupts: device interrupt > >> > +- clocks: UART reference clock used to derive the baudrate (only > >> > + mandatory with "marvell,armada-3700-uart-ext" > >> > compatible). > >> > >> How is this optional? The freq is fixed if not present? If so, what > >> frequency? > > > > The "clocks" property should not be optional at all but that is how > > the bindings were handled before this series, so I can't tell now > > that this property is mandatory as it would break compatibility > > with older versions of the driver. > > Okay. I think it should be mandatory with a note how missing property > is handled. Sure. > > > When no clock is provided, the frequency is fixed by the bootloader > > and cannot be changed. There is no standard frequency for it but the > > one chosen by the bootloader often is 115200 as the UART is usually > > used as the serial console. > > > > Because the bootloader does only initialize the UART in use for the > > serial console, the clock is mandatory when using another port or it > > will not work at all. Thank you, Miquèl -- Miquel Raynal, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
