> -----Original Message----- > From: linux-can-owner@xxxxxxxxxxxxxxx <linux-can-owner@xxxxxxxxxxxxxxx> > On Behalf Of Pankaj Bansal > Sent: 2019年5月16日 16:12 > To: Leo Li <leoyang.li@xxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Mark > Rutland <mark.rutland@xxxxxxx>; Wolfgang Grandegger > <wg@xxxxxxxxxxxxxx>; Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> > Cc: linux-can@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx > Subject: [PATCH v2 1/2] Documentation: can: flexcan: Add flexcan clocks' > information > > The clocking information is missing from flexcan device tree bindings. > This information is needed to be able to use flexcan. Document the same. > > Signed-off-by: Pankaj Bansal <pankaj.bansal@xxxxxxx> > --- > > Notes: > Dependencies: > - > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.ker > nel.org%2Fpatchwork%2Fcover%2F1024536%2F&data=02%7C01%7Cqia > ngqing.zhang%40nxp.com%7C42617583d2c242521a8e08d6d9d63ee7%7C68 > 6ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636935911534405181&a > mp;sdata=UOC7mIHPsnZbK2742mTjYkL3%2BmC7EqUP4E127UM5bWY%3D& > amp;reserved=0 > > V2: > - Removed clock-frequency from optional properties > - Added Dependencies in Notes > > .../bindings/net/can/fsl-flexcan.txt | 46 +++++++++++++++++- > 1 file changed, 44 insertions(+), 2 deletions(-) > > diff --git a/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt > b/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt > index a04168605998..73c616ca0f9a 100644 > --- a/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt > +++ b/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt > @@ -12,9 +12,42 @@ Required properties: > - reg : Offset and length of the register set for this device > - interrupts : Interrupt tuple for this device > > -Optional properties: > +Clocking information is must for flexcan. please refer below info for > +understanding clocking in flexcan: > + > +• The FLEXCAN module is divided into two blocks. Controller host > +interface > + ("CHI") and Protocol Engine ("PE") > +• Both these blocks require clock. > +• CHI is responsible for registers read write including MB read/write. > + While PE is responsible for Transfer/receive data on CAN bus. > +• The clocks feeding to these two blocks can be synchronous (i.e. same > +clock) > + or asynchronous (i.e. separate clocks). > +• Selection is made in the CLK_SRC bit (bit 13) of Control 1 Register. > + - CLK_SRC = 0, asynchronous i.e. separate clocks for CHI and PE > + - CLK_SRC = 1, synchronous i.e. CHI clock is used for PE and PE > + clock is not used. > +• If this bit is not implemented in SOC, then SOC only supports > +asynchronous > + clocks. > +• Either of the clock can be generated by any of the clock source. > +• When the two clocks are asynchronous, then following restrictions > +apply to > + PE clock. > + - PE clock must be less than CHI clock. > +• If low jitter is required on CAN bus, dedicated oscillator can be > +used to > + provide PE clock, but it must be less than CHI clock. > + > +Base on above information clocking info in flexcan can be defined in two > ways: > + > +Method 1(Preferred): > + - clocks: phandle to the clocks feeding the flexcan. Two can be given: > + - "ipg": Protocol Engine clock > + - "per": Controller host interface clock [Joakim Zhang] In flexcan driver now, "ipg" is for CHI clock, "per" is for PE clock. I think it's unnecessary to exchange here. Best Regards, Joakim Zhang > + - clock-names: Must contain the clock names described just above. > > -- clock-frequency : The oscillator frequency driving the flexcan device > +Method 2(Not Preferred): > + - clock-frequency : The synchronous clock frequency supplied to both > + Controller host interface and Protocol Engine > + > +Optional properties: > > - xceiver-supply: Regulator that powers the CAN transceiver > > @@ -47,5 +80,14 @@ Example: > interrupts = <48 0x2>; > interrupt-parent = <&mpic>; > clock-frequency = <200000000>; // filled in by bootloader > + }; > + > + can@2180000 { > + compatible = "fsl,lx2160ar1-flexcan"; > + reg = <0x0 0x2180000 0x0 0x10000>; > + interrupts = <GIC_SPI 21 IRQ_TYPE_LEVEL_HIGH>; > + clocks = <&sysclk>, <&clockgen 4 7>; > + clock-names = "ipg", "per"; > fsl,clk-source = <0>; // select clock source 0 for PE > + status = "disabled"; > }; > -- > 2.17.1
