linux-kernel - Re: [PATCH] mmc: sunxi: mask all Response Timeout error messages

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Date:   Tue, 7 Mar 2017 11:10:14 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Icenowy Zheng <icenowy@...c.xyz>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>, Chen-Yu Tsai <wens@...e.org>,
        Hans de Goede <hdegoede@...hat.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: sunxi: mask all Response Timeout error messages

On Tue, Mar 07, 2017 at 01:28:42AM +0800, Icenowy Zheng wrote:
> 
> 
> 06.03.2017, 23:53, "Maxime Ripard" <maxime.ripard@...e-electrons.com>:
> > On Mon, Mar 06, 2017 at 06:32:41PM +0800, Icenowy Zheng wrote:
> >>  06.03.2017, 18:04, "Maxime Ripard" <maxime.ripard@...e-electrons.com>:
> >>  > Hi,
> >>  >
> >>  > On Mon, Mar 06, 2017 at 12:45:35AM +0800, Icenowy Zheng wrote:
> >>  >>  Response Timeout is very usual: it will happen when trying to run some
> >>  >>  commands that do not belong to the card; it will happen when some SDIO
> >>  >>  card transfer beyond its SDIO bandwidth; and when the MMC controller is
> >>  >>  set to poll the card with "broken-cd" property (the Lichee Pi series of
> >>  >>  boards do this), it will flood to the console and make the console
> >>  >>  unusable.
> >>  >>
> >>  >>  Mask all response-timeout-only error messages, only show it when another
> >>  >>  error happens.
> >>  >>
> >>  >>  Signed-off-by: Icenowy Zheng <icenowy@...c.xyz>
> >>  >>  ---
> >>  >>   drivers/mmc/host/sunxi-mmc.c | 13 +++++++++----
> >>  >>   1 file changed, 9 insertions(+), 4 deletions(-)
> >>  >>
> >>  >>  diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> >>  >>  index 6ffcd2838272..7828e1f57cf0 100644
> >>  >>  --- a/drivers/mmc/host/sunxi-mmc.c
> >>  >>  +++ b/drivers/mmc/host/sunxi-mmc.c
> >>  >>  @@ -483,10 +483,15 @@ static void sunxi_mmc_dump_errinfo(struct sunxi_mmc_host *host)
> >>  >>           struct mmc_command *cmd = host->mrq->cmd;
> >>  >>           struct mmc_data *data = host->mrq->data;
> >>  >>
> >>  >>  - /* For some cmds timeout is normal with sd/mmc cards */
> >>  >>  - if ((host->int_sum & SDXC_INTERRUPT_ERROR_BIT) ==
> >>  >>  - SDXC_RESP_TIMEOUT && (cmd->opcode == SD_IO_SEND_OP_COND ||
> >>  >>  - cmd->opcode == SD_IO_RW_DIRECT))
> >>  >>  + /*
> >>  >>  + * Reading timeout is usually normal, especially when doing
> >>  >>  + * card-polling with "broken-cd" in device tree.
> >>  >>  + * If do not mask it, the RTO error message will flood the console
> >>  >>  + * and even hide useful error messages.
> >>  >>  + *
> >>  >>  + * Some SDIO commands will also normally timeout with non-SDIO cards.
> >>  >>  + */
> >>  >>  + if ((host->int_sum & SDXC_INTERRUPT_ERROR_BIT) == SDXC_RESP_TIMEOUT)
> >>  >
> >>  > We really shouldn't silence legit errors.
> >>  >
> >>  > The actual problem here is that we log them as error, we could
> >>  > probably reduce it to debug.
> >>
> >>  Even if it's reduced to debug, it will still flush dmesg buffers.
> >
> > No, it will not even be compiled by default.
> >
> >>  Or make it only visible when "debug" parameter is present in kernel
> >>  cmdline?
> >
> > debug messages are visible in dmesg only if DEBUG is defined, which is
> > only happening if CONFIG_MMC_DEBUG is set. This won't affect the
> > general case in any way.
> >
> > And it is output only if loglevel is set higher than 7.
> 
> Should I make all error messages debug level or only make "RTO"-only
> error to debug level like I currently do?

I'd say just change the level of the log of the line coming below that
one. It doesn't provide any useful clue about what's going on anyway,
there's nothing the user will be able to do to prevent that, and
someone willing to debug it will have to turn on the debug options
anway.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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