linux-kernel - Re: [PATCH] mips: bmips: BCM6358: disable arch_sync_dma_for_cpu

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Message-ID: <CAKR-sGcyMF26NGoeEApKuKDe6=14nCGKwRYx-o68LHAcmUNXhA@mail.gmail.com>
Date:   Mon, 13 Mar 2023 22:39:19 +0100
From:   Álvaro Fernández Rojas <noltari@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     William Zhang <william.zhang@...adcom.com>,
        Jonas Gorski <jonas.gorski@...il.com>,
        bcm-kernel-feedback-list@...adcom.com, tsbogend@...ha.franken.de,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mips: bmips: BCM6358: disable arch_sync_dma_for_cpu_all()

Hi Florian,

I did another test changing from TP1 to TP0 and this is the result:
[ 0.000000] Linux version 5.15.98 (noltari@...antis)
(mips-openwrt-linux-musl-gcc (OpenWrt GCC 12.2.0 r22187+1-19817fa3f5)
12.2.0, GNU ld (GNU Binutils) 2.40.0) #0 SMP Sun Mar 12 18:23:28 2023
[ 0.000000] bmips_cpu_setup: read_c0_brcm_config_0() = 0xe30e1006
[ 0.000000] bmips_cpu_setup: BMIPS_RAC_CONFIG = 0x2a00015
[ 0.000000] CPU0 revision is: 0002a010 (Broadcom BMIPS4350)

And there were no exceptions with EHCI/OHCI as opposed to TP1.
So the issue is only happening when booting from TP1.
Maybe it's due to the fact that BCM6358 has a shared TLB?

Maybe the correct way of solving the issue would be by adding the
following code at bcm6358_quirks():
if (read_c0_brcm_cmt_local() & (1 << 31))
    bmips_dma_sync_disabled = 1;

BTW, if I understood it correctly, you want me to reverse the logic,
so bmips_dma_sync_disabled instead of bmips_dma_sync_enabled.
Is this correct?

Best regards,
Álvaro.


El lun, 13 mar 2023 a las 18:37, Florian Fainelli
(<f.fainelli@...il.com>) escribió:
>
> On 3/12/23 11:50, Álvaro Fernández Rojas wrote:
> > Hi Florian,
> >
> > I tried what you suggested but it stil panics on EHCI:
> >
> > [    0.000000] Linux version 5.15.98 (noltari@...antis)
> > (mips-openwrt-linux-musl-gcc (OpenWrt GCC 12.2.0 r22187+1-19817fa3f5)
> > 12.2.0, GNU ld (GNU Binutils) 2.40.0) #0 SMP Sun Mar 12 18:23:28 2023
> > [    0.000000] bmips_cpu_setup: read_c0_brcm_config_0() = 0xe30e1006
> > [    0.000000] bmips_cpu_setup: cbr + BMIPS_RAC_CONFIG = 0x3c1b8041
> > [    0.000000] CPU0 revision is: 0002a010 (Broadcom BMIPS4350)
> >
> > It looks like bit 29 is set so RAC should be present.
> > And RAC_I seems to be set, but not RAC_D...
> >
> > BTW, this is what I added to bmips_cpu_setup:
> >
> > case CPU_BMIPS4350:
> > cfg = read_c0_brcm_config_0();
> > pr_info("bmips_cpu_setup: read_c0_brcm_config_0() = 0x%x\n", cfg);
> >
> > cfg = __raw_readl(cbr + BMIPS_RAC_CONFIG);
> > pr_info("bmips_cpu_setup: cbr + BMIPS_RAC_CONFIG = 0x%x\n", cfg);
> > __raw_writel(cfg | BIT(0) | BIT(1), cbr + BMIPS_RAC_CONFIG);
> > __raw_readl(cbr + BMIPS_RAC_CONFIG);
> > break;
>
> Thanks for running those experiments, I cannot explain what you are
> seeing, so there must be some sort of erratum applicable to the
> BMIPS4380 revision used on the 6358 somehow...
>
> If you can make the suggested change to use negative logic in order to
> disable the RAC flushing, that would work for me, also maybe add a
> Fixes: tag so it gets backported to stable trees?
>
> Thanks!
> --
> Florian
>