> -----Original Message----- > From: Joakim Zhang > Sent: Friday, 17 May, 2019 03:38 PM > 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: Pankaj Bansal > > Sent: 2019年5月17日 17:12 > > To: Joakim Zhang <qiangqing.zhang@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: 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%2F > > > > lo > > > > re > > > > .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#L136 > > 5 > > > > And clock_freq is being calculated using "per". > > https://elixir.bootlin.com/linux/v5.1.3/source/drivers/net/can/flexcan > > .c#L151 > > 5 > > > > Therefore, "per" is the CHI clock and "ipg" is PE clock. > > As you said, clock_freq calculated by "per", and you can find that priv- > >can.clock.freq = clock_freq. > And can.clock.freq is used to calculate TQ. You know PE clock is for CAN bus. So > I think "per" is for PE. PER is being used for CHI as well as PE (because CTRL[CLK_SRC] = 1 https://elixir.bootlin.com/linux/v5.1.3/source/drivers/net/can/flexcan.c#L136) ONLY CHI clock can be supplied to both CHI and PE. (PE clock can only be supplied to PE provided CTRL[CLK_SRC] = 0, and PE clock < CHI clock ) > > Did I misunderstand? > > Best Regards, > Joakim Zhang > > > 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
