linux-kernel - Re: [RESEND PATCH v5 1/5] driver core: add probe

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Message-ID: <6373a4eb-2f1b-b56f-48a8-ae97b4e4476a@arm.com>
Date:   Wed, 24 Jun 2020 16:00:34 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Neil Armstrong <narmstrong@...libre.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [RESEND PATCH v5 1/5] driver core: add probe_err log helper

On 2020-06-24 15:02, Mark Brown wrote:
> On Wed, Jun 24, 2020 at 04:45:28PM +0300, Andy Shevchenko wrote:
>> On Wed, Jun 24, 2020 at 4:27 PM Mark Brown <broonie@...nel.org> wrote:
> 
>>> As I said down the thread that's not a great pattern since it means that
>>> probe deferral errors never get displayed and users have a hard time
>>> figuring out why their driver isn't instantiating.
> 
>> Don't we have a file in the debugfs to list deferred drivers?
> 
> Part of what this patch series aims to solve is that that list is not
> very useful since it doesn't provide any information on how things got
> deferred which means it's of no use in trying to figure out any
> problems.
> 
>> In the case of deferred probes the errors out of it makes users more
>> miserable in order to look through tons of spam and lose really useful
>> data in the logs.
> 
> I seem to never manage to end up using any of the systems which generate
> excessive deferrals.

Be thankful... And count me in as one of those miserable users; here's one
of mine being bad enough without even printing any specific messages about
deferring ;)

Robin.

-----

[robin@...sel-cheese ~]$ dmesg | grep dwmmc
[    3.046297] dwmmc_rockchip ff0c0000.mmc: IDMAC supports 32-bit address mode.
[    3.054312] dwmmc_rockchip ff0c0000.mmc: Using internal DMA controller.
[    3.061774] dwmmc_rockchip ff0c0000.mmc: Version ID is 270a
[    3.068101] dwmmc_rockchip ff0c0000.mmc: DW MMC controller at irq 30,32 bit host data width,256 deep fifo
[    3.079638] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[    3.087678] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[    3.095134] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[    3.101480] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[    3.113071] dwmmc_rockchip ff0f0000.mmc: IDMAC supports 32-bit address mode.
[    3.121110] dwmmc_rockchip ff0f0000.mmc: Using internal DMA controller.
[    3.128565] dwmmc_rockchip ff0f0000.mmc: Version ID is 270a
[    3.134886] dwmmc_rockchip ff0f0000.mmc: DW MMC controller at irq 32,32 bit host data width,256 deep fifo
[    3.948510] dwmmc_rockchip ff0c0000.mmc: IDMAC supports 32-bit address mode.
[    3.956475] dwmmc_rockchip ff0c0000.mmc: Using internal DMA controller.
[    3.963884] dwmmc_rockchip ff0c0000.mmc: Version ID is 270a
[    3.970133] dwmmc_rockchip ff0c0000.mmc: DW MMC controller at irq 30,32 bit host data width,256 deep fifo
[    4.141231] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[    4.149178] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[    4.156582] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[    4.162823] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[    4.175606] dwmmc_rockchip ff0f0000.mmc: IDMAC supports 32-bit address mode.
[    4.183540] dwmmc_rockchip ff0f0000.mmc: Using internal DMA controller.
[    4.190946] dwmmc_rockchip ff0f0000.mmc: Version ID is 270a
[    4.197196] dwmmc_rockchip ff0f0000.mmc: DW MMC controller at irq 32,32 bit host data width,256 deep fifo
[    4.250758] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[    4.258688] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[    4.266104] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[    4.272358] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[    4.285390] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[    4.293333] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[    4.300750] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[    4.307005] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[    4.971373] dwmmc_rockchip ff0f0000.mmc: Successfully tuned phase to 134
[    5.027225] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[    5.035339] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[    5.042769] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[    5.049050] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[   24.727583] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[   24.745541] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[   24.753003] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[   24.763289] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[   25.589620] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[   25.603066] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[   25.615283] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[   25.627911] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[   25.643469] dwmmc_rockchip ff0d0000.mmc: IDMAC supports 32-bit address mode.
[   25.651532] dwmmc_rockchip ff0d0000.mmc: Using internal DMA controller.
[   25.658960] dwmmc_rockchip ff0d0000.mmc: Version ID is 270a
[   25.665246] dwmmc_rockchip ff0d0000.mmc: DW MMC controller at irq 31,32 bit host data width,256 deep fifo
[   25.677154] dwmmc_rockchip ff0d0000.mmc: allocated mmc-pwrseq