> -----Original Message----- > From: Joakim Zhang > Sent: Friday, 17 May, 2019 06:41 AM > To: Pankaj Bansal <pankaj.bansal@xxxxxxx>; 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: RE: [PATCH v2 1/2] Documentation: can: flexcan: Add flexcan clocks' > information > > > > -----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. In flexcan driver now, same is clock supplied to both CHI and PE blocks using CTRL[CLK_SRC] = 1 https://elixir.bootlin.com/linux/v5.1.3/source/drivers/net/can/flexcan.c#L1365 And clock_freq is being calculated using "per". https://elixir.bootlin.com/linux/v5.1.3/source/drivers/net/can/flexcan.c#L1515 Therefore, "per" is the CHI clock and "ipg" is PE clock. > > 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
