Messages in this thread | | | Date | Wed, 9 Mar 2022 13:16:32 +0100 | From | 'Horatiu Vultur' <> | Subject | Re: [PATCH net-next] net: lan966x: Improve the CPU TX bitrate. |
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The 03/09/2022 09:57, David Laight wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > From: 'Horatiu Vultur' > > Sent: 09 March 2022 09:11 > > > > The 03/08/2022 22:46, David Laight wrote: > > > > > > From: Horatiu Vultur > > > > Sent: 08 March 2022 22:30 > > > > > > > > The 03/08/2022 22:36, Andrew Lunn wrote: > > > > > > > > > > > static int lan966x_port_inj_ready(struct lan966x *lan966x, u8 grp) > > > > > > { > > > > > > - u32 val; > > > > > > + unsigned long time = jiffies + usecs_to_jiffies(READL_TIMEOUT_US); > > > > > > + int ret = 0; > > > > > > > > > > > > - return readx_poll_timeout_atomic(lan966x_port_inj_status, lan966x, val, > > > > > > - QS_INJ_STATUS_FIFO_RDY_GET(val) & BIT(grp), > > > > > > - READL_SLEEP_US, READL_TIMEOUT_US); > > > > > > + while (!(lan_rd(lan966x, QS_INJ_STATUS) & > > > > > > + QS_INJ_STATUS_FIFO_RDY_SET(BIT(grp)))) { > > > > > > + if (time_after(jiffies, time)) { > > > > > > + ret = -ETIMEDOUT; > > > > > > + break; > > > > > > + } > > > > > > > > > > Did you try setting READL_SLEEP_US to 0? readx_poll_timeout_atomic() > > > > > explicitly supports that. > > > > > > > > I have tried but it didn't improve. It was the same as before. > > > > > > How many times round the loop is it going ? > > > > In the tests that I have done, I have never seen entering in the loop. > > In which case I'd do an initial status check before even > faffing with 'jiffies'.
That is a good idea. I will do this change in the next version.
> > It might even be that the status read is so slow that space > is always available by the time it is processed. > PCIe reads can be horribly slow. > Into our fgpa they end up being slower than old ISA bus cycles. > Probably several thousand cpu clocks. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales)
-- /Horatiu
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