Messages in this thread | | | Subject | Re: [PATCH RESEND] net: can: Introduce MEN 16Z192-00 CAN controller driver | From | Wolfgang Grandegger <> | Date | Tue, 9 Aug 2016 13:54:30 +0200 |
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Am 09.08.2016 um 08:10 schrieb Andreas Werner: > On Mon, Aug 08, 2016 at 04:35:34PM +0200, Wolfgang Grandegger wrote: >> Am 08.08.2016 um 16:05 schrieb Andreas Werner: >>> On Mon, Aug 08, 2016 at 02:28:39PM +0200, Wolfgang Grandegger wrote:
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>>>>>>> + >>>>>>> + ndev = alloc_candev(sizeof(struct men_z192), 1); >>>>>> >>>>>> You specify here one echo_skb but it's not used anywhere. Local loopback >>>>>> seems not to be implemented. >>>>>> >>>>> >>>>> Agree with you, will set it to "0". >>>> >>>> No, the local loopback is mandetory! >>>> >>> >>> Hm ok, but if i check alloc_candev() in drivers/net/can/dev.c >>> it is not mandatory. In the Documentation/networking/can.txt >>> there is also a "should" and a fallback mechnism if the driver >>> does not support the local loopback. >> >> Well, s/driver/hardware/ ! Local loopback is the preferred mechanism. >> > > Sure... > >>> I'm currently ok with this fallback mechanism. >>> >>> Anyway I am not sure that the driver can handle the echo skb correctly. >>> If i understand it correctly, the can_get_echo_skb() is normally called >>> on a "TX done IRQ" to get the skb and loop it back. >>> I do not have such a "TX done IRQ" and have not implemented implemented >>> and added the local looback. >> >> What does "MEN_Z192_TFLG_TXIF" signal? >> > > It is not a "TX Done" IRQ, it is the tx buffer level IRQ. > The IRQ is triggered when the number of available tx buffer entries is as > configured with txlvl. (after the buffer was full) > > Example: > txlvl = 0 > tx buffer has 255 entries. > > -> The IRQ is triggered as soon as 1 frame got transmitted (254 entries). > > --- > > txlvl = 254 > tx buffer has 255 entries. > > -> The IRQ is triggered as soon as the buffer has one entry and it got transmitted > > >>> May be I can put and get the echo skb within the xmit function? >>> Does this make sense? >> >> It only makes sense if the driver knows when one or more transfers are done. >> > > Then i do not think that I can use the txlvl IRQ in this case and need to use > the fallback mechanism.
You could store "MEN_Z192_TX_BUF_CNT(readl(®s->rx_tx_sts))" in the start_xmit function and check again in the isr function to find out how much transfers have been transmitted in the meantime. Does it make sense?
Wolfgang.
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