linux-kernel - Re: [PATCH v1 0/4] Add tracing for SDHCI register access

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Message-ID: <20190412145012.GA101407@google.com>
Date:   Fri, 12 Apr 2019 08:50:12 -0600
From:   Raul Rangel <rrangel@...omium.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     linux-trace-devel@...r.kernel.org, linux-mmc@...r.kernel.org,
        djkurtz@...omium.org, zwisler@...omium.org,
        Ludovic Barre <ludovic.barre@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Faiz Abbas <faiz_abbas@...com>, linux-kernel@...r.kernel.org,
        Oleksij Rempel <linux@...pel-privat.de>,
        Liming Sun <lsun@...lanox.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Ingo Molnar <mingo@...hat.com>,
        Prabu Thangamuthu <Prabu.T@...opsys.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v1 0/4] Add tracing for SDHCI register access

On Fri, Apr 12, 2019 at 09:26:44AM +0300, Adrian Hunter wrote:
> On 12/04/19 1:08 AM, Raul E Rangel wrote:
> > I was debugging a SDHC hardware bug and got tired of having to
> > translate the register values by hand. This patch set makes it so all
> > SDHC register read and write operations can be traced and easily read by
> > a human.
> 
> While this might be useful for people unfamiliar with SDHCI, I am not sure
> it should be in the upstream kernel.
Can you help me understand your hesitation? Would you prefer removing the
pretty printing? Or would you prefer not having any trace events at all?

The xhci driver has a bunch of pretty print trace events that make it
invaluable when debugging.
https://github.com/torvalds/linux/blob/d7563ca5bfca53398e100eb74345c5d3ef06bf9d/drivers/usb/host/xhci.h#L2160

> Also, it doesn't seem ideal for every
> driver to add its own plumbing for such a feature.
What do you mean by every driver having to add it's own plumbing? Any
driver that uses sdhci_readX or sdhci_writeX get the functionality for
free.

Thanks,
Raul