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Subject: Re: [PATCH v2 1/1] mmc: host: meson-gx-mmc: fix possible deadlock
 condition for preempt_rt
To:     Kevin Hilman <khilman@baylibre.com>,
        linux-amlogic@lists.infradead.org, linux-mmc@vger.kernel.org
Cc:     linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, bigeasy@linutronix.de
References: <20200927025418.12382-1-bjharper@gmail.com>
 <20200927025418.12382-2-bjharper@gmail.com> <7hwo0dmnbt.fsf@baylibre.com>
From:   Brad Harper <bjharper@gmail.com>
Message-ID: <aaf796cc-7e6e-2831-5b13-9654f8e6fc77@gmail.com>
Date:   Tue, 29 Sep 2020 18:32:24 +1000
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Hi Kevin,

     I think you are right,  I don't have a good enough understanding to 
make this work so please disregard the patch.  I will take on 
Sebastian's advice and do some testing with 'threadirqs' parameter 
enabled in standard kernel to see if I can reproduce my original issue 
there.  I'm hoping Jerome might also be able to help with some time to 
find proper solution.

Many Thanks,

Brad.

On 29/09/2020 10:35 am, Kevin Hilman wrote:
> Brad Harper <bjharper@gmail.com> writes:
>
>> ---
>>   drivers/mmc/host/meson-gx-mmc.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> This patch still needs changelog summarizing the problem and what is
> being fixed by the patch.  Most of what's in the cover letter belongs
> here.
>
> The cover letter can be used to describe the history/background that you
> don't want in the patch itself.  Alternatviely, you could include that
> information in the a single patch email also because everything after
> the "---" line does not end up in git history.
>
>> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
>> index 08a3b1c05..3ba8f988d 100644
>> --- a/drivers/mmc/host/meson-gx-mmc.c
>> +++ b/drivers/mmc/host/meson-gx-mmc.c
>> @@ -146,6 +146,7 @@ struct sd_emmc_desc {
>>   };
>>   
>>   struct meson_host {
>> +	spinlock_t		lock;
>>   	struct	device		*dev;
>>   	struct	meson_mmc_data *data;
>>   	struct	mmc_host	*mmc;
>> @@ -1051,6 +1052,7 @@ static int meson_mmc_probe(struct platform_device *pdev)
>>   	host->mmc = mmc;
>>   	host->dev = &pdev->dev;
>>   	dev_set_drvdata(&pdev->dev, host);
>> +	spin_lock_init(&host->lock);
> I'm confused about what this lock is intended to do.  You init it here,
> but it's never used anywhere.
>
>>   	/* The G12A SDIO Controller needs an SRAM bounce buffer */
>>   	host->dram_access_quirk = device_property_read_bool(&pdev->dev,
>> @@ -1139,7 +1141,7 @@ static int meson_mmc_probe(struct platform_device *pdev)
>>   	       host->regs + SD_EMMC_IRQ_EN);
>>   
>>   	ret = request_threaded_irq(host->irq, meson_mmc_irq,
>> -				   meson_mmc_irq_thread, IRQF_ONESHOT,
>> +				   meson_mmc_irq_thread, 0,
>>   				   dev_name(&pdev->dev), host);
>>   	if (ret)
>>   		goto err_init_clk;
> Kevin