linux-kernel - Re: [PATCH v3] mmc: Convert from tasklet to BH workqueue

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Date: Fri, 21 Jun 2024 11:06:37 +0100
From: Christian Loehle <christian.loehle@....com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Allen Pais <allen.lkml@...il.com>,
 Aubin Constans <aubin.constans@...rochip.com>,
 Ulf Hansson <ulf.hansson@...aro.org>,
 Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Claudiu Beznea <claudiu.beznea@...on.dev>,
 Manuel Lauss <manuel.lauss@...il.com>,
 Michał Mirosław <mirq-linux@...e.qmqm.pl>,
 Jaehoon Chung <jh80.chung@...sung.com>, Aaro Koskinen
 <aaro.koskinen@....fi>, Adrian Hunter <adrian.hunter@...el.com>,
 Florian Fainelli <florian.fainelli@...adcom.com>, Ray Jui
 <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Alex Dubov <oakad@...oo.com>,
 Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
 Masami Hiramatsu <mhiramat@...nel.org>, Bruce Chang <brucechang@....com.tw>,
 Harald Welte <HaraldWelte@...tech.com>, Pierre Ossman <pierre@...man.eu>,
 linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v3] mmc: Convert from tasklet to BH workqueue

On 6/21/24 10:53, Wolfram Sang wrote:
> Hi,
> 
> On Tue, Jun 18, 2024 at 03:52:07PM GMT, Allen Pais wrote:
>> The only generic interface to execute asynchronously in the BH context is
>> tasklet; however, it's marked deprecated and has some design flaws. To
>> replace tasklets, BH workqueue support was recently added. A BH workqueue
>> behaves similarly to regular workqueues except that the queued work items
>> are executed in the BH context.
>>
>> This patch converts drivers/mmc/* from tasklet to BH workqueue.
>>
>> Based on the work done by Tejun Heo <tj@...nel.org>
> 
> Has this been fully build-tested?

Obviously not, FWIW I noted this on v1:
https://lore.kernel.org/linux-mmc/9c31b697-3d80-407a-82b3-cfbb19fafb31@arm.com/
But hadn't looked at the patch since then, sorry.

> 
> ===
> drivers/mmc/host/renesas_sdhi_internal_dmac.c: In function ‘renesas_sdhi_internal_dmac_complete_work_fn’:
> ./include/linux/container_of.h:20:54: error: ‘struct tmio_mmc_host’ has no member named ‘dma_complete’
> ===
> 
> In deed, 'dma_complete' is only in 'struct renesas_sdhi_dma'. From
> there, we can get to the parent 'struct renesas_sdhi' using
> container_of. But then, I don't see a way to go to 'struct
> tmio_mmc_host' from there. The other way around is possible because
> there is the pointer 'struct tmio_mmc_data *pdata' in the TMIO struct
> pointing to the data contained in 'struct renesas_sdhi'. 'host_to_priv()'
> does the math. But I don't see a path the other way around.
> 
> So, it doesn't look like the workqueue interface can provide a
> generic pointer like tasklets could do? This means we have to add a
> pointer from 'struct renesas_sdhi' to 'struct tmio_mmc_host'?
> 
> All the best,
> 
>    Wolfram
>