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

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Message-ID: <21d7f0c8-9a61-4759-b655-b12a6fad9885@intel.com>
Date: Mon, 6 Oct 2025 10:38:22 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Michael Garofalo <officialtechflashyt@...il.com>, <ulf.hansson@...aro.org>
CC: <linux-mmc@...r.kernel.org>, <linux-kernel@...r.kernel.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.

> 
> 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(-)
>>
>