linux-kernel - Re: [PATCH 0/2] mmc: sdhci: add quirk to disable bounce buffer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251006092815.2555733-1-officialTechflashYT@gmail.com>
Date: Mon,  6 Oct 2025 02:28:15 -0700
From: Michael Garofalo <officialtechflashyt@...il.com>
To: adrian.hunter@...el.com
Cc: linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org,
	officialtechflashyt@...il.com,
	ulf.hansson@...aro.org
Subject: Re: [PATCH 0/2] mmc: sdhci: add quirk to disable bounce buffer

> On 06/10/2025 10:35, Adrian Hunter wrote:
>> On 06/10/2025 04:36, Michael Garofalo wrote:
>>> This patch series adds a new bit to quirks2 for disabling the bounce
>>> buffer.  On some hardware, this is required for proper operation.  An
>>> example of such hardware is the SDHCI controller of the Nintendo Wii's
>>> "Hollywood" chipset.  Without this patch, the onboard Broadcom 4318
>>> Wi-Fi fails to connect to any networks.
>> 
>> The bounce buffer should not make any difference, so it is likely
>> a different problem that gets hidden when the bounce buffer is not
>> used.
>> 
>>> Could you enable dynamic debug messages and show the messages
>>> for the failing case?
>>
>>Actually will also need to see the messages in the "fixed" case
>>to compare.
I'm afraid I won't be able to provide those easily, at least not with the
commands you've provided.  Since the rootfs is _also_ running from SD,
turning on full MMC logs like this produces an obscene amount of noise
from the storage, unrelated to the SDIO wireless.  It gets even worse with
my original intention, which was to save the logs to SD Card, (since my USB
Gecko serial console is rather flakey, and introduces corruption now and then),
since it's now logging the writes of it's own logs in a permanent loop.
If there's a way to narrow down the logs to specifically whatever portions
you're interested in, and filter out the noise, I would happily provide it.

(P.S. sorry about the blank message there, still working out how to deal with mailing lists)
>
>> 
>> Dynamic debug for mmc
>> ---------------------
>> 
>>     Kernel must be configured:
>> 
>>         CONFIG_DYNAMIC_DEBUG=y
>> 
>>     To enable mmc debug via sysfs:
>> 
>>         echo 'file drivers/mmc/core/* +p' > /sys/kernel/debug/dynamic_debug/control
>>         echo 'file drivers/mmc/host/* +p' > /sys/kernel/debug/dynamic_debug/control
>> 
>>     To enable mmc debug via kernel command line:
>> 
>>         dyndbg="file drivers/mmc/core/* +p;file drivers/mmc/host/* +p"
>> 
>>     To disable mmc debug:
>> 
>>         echo 'file drivers/mmc/core/* -p' > /sys/kernel/debug/dynamic_debug/control
>>         echo 'file drivers/mmc/host/* -p' > /sys/kernel/debug/dynamic_debug/control
>> 
>>     More general information in kernel documentation in kernel tree:
>> 
>>         Documentation/admin-guide/dynamic-debug-howto.rst
>> 	https://www.kernel.org/doc/html/latest/admin-guide/dynamic-debug-howto.html
>> 
>> 
>>>
>>> Patch 1 introduces the new quirk bit.
>>> Patch 2 applies it to sdhci-of-hlwd.
>>>
>>> Michael Garofalo (2):
>>>   mmc: sdhci: add quirk to disable the bounce buffer
>>>   mmc: sdhci-of-hlwd: disable bounce buffer usage
>>>
>>>  drivers/mmc/host/sdhci-of-hlwd.c | 1 +
>>>  drivers/mmc/host/sdhci.c         | 8 +++++---
>>>  drivers/mmc/host/sdhci.h         | 4 ++++
>>>  3 files changed, 10 insertions(+), 3 deletions(-)
>>>
>>