Re: [PATCH V2 03/27] mmc: mmci: convert dma_setup callback to return an int

From: Ludovic BARRE <ludovic.barre@st.com>
To: Ulf Hansson <ulf.hansson@linaro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Benjamin Gaignard <benjamin.gaignard@linaro.org>,
	Gerald Baeza <gerald.baeza@st.com>,
	Loic Pallardy <loic.pallardy@st.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	DTML <devicetree@vger.kernel.org>,
	"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
	<linux-stm32@st-md-mailman.stormreply.com>
Subject: Re: [PATCH V2 03/27] mmc: mmci: convert dma_setup callback to return an int
Date: Mon, 24 Sep 2018 18:12:44 +0200	[thread overview]
Message-ID: <15c31e3b-646a-f5db-b45a-3e2f556d9fd5@st.com> (raw)
In-Reply-To: <CAPDyKFqnN0gg9WsbNPQcodqUXJmFEzMM+ST36s6oEZ2OPoONug@mail.gmail.com>

hi Ulf

On 09/24/2018 04:28 PM, Ulf Hansson wrote:
> On 21 September 2018 at 11:45, Ludovic Barre <ludovic.Barre@st.com> wrote:
>> From: Ludovic Barre <ludovic.barre@st.com>
>>
>> This patch converts dma_setup callback to return an integer
>> This patch is needed to prepare sdmmc variant with internal dma
>>
>> Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
>> ---
>>   drivers/mmc/host/mmci.c          | 14 ++++++++++----
>>   drivers/mmc/host/mmci.h          |  2 +-
>>   drivers/mmc/host/mmci_qcom_dml.c |  6 ++++--
>>   3 files changed, 15 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
>> index cbd67bc..2f845f3 100644
>> --- a/drivers/mmc/host/mmci.c
>> +++ b/drivers/mmc/host/mmci.c
>> @@ -415,7 +415,7 @@ static void mmci_init_sg(struct mmci_host *host, struct mmc_data *data)
>>    * no custom DMA interfaces are supported.
>>    */
>>   #ifdef CONFIG_DMA_ENGINE
>> -static void mmci_dma_setup(struct mmci_host *host)
>> +static int mmci_dma_setup(struct mmci_host *host)
>>   {
>>          const char *rxname, *txname;
>>
>> @@ -466,7 +466,9 @@ static void mmci_dma_setup(struct mmci_host *host)
>>          }
>>
>>          if (host->ops && host->ops->dma_setup)
>> -               host->ops->dma_setup(host);
>> +               return host->ops->dma_setup(host);
>> +
> 
> Looks like you need to implement a error handling, instead of just
> returning the error code.

yes, today if a dma_setup is defined, we can't fallback to pio mode.
A use_dma variable (defined in mmci_host) could be setted follow the 
return code of ops->dma_setup

example:

void mmci_dma_setup(struct mmci_host *host)
{
	int err;

	if (!host->ops || !host->ops->dma_setup)
		return;

	err = host->ops->dma_setup(host);
	if (err)
		return;

	host->use_dma = true;

	/* initialize pre request cookie */
	host->next_cookie = 1;
}

use_dma variable could be check by mmci_host_ops variant functions.

are you agree with this proposal?

> 
>> +       return 0;
>>   }
>>
>>   /*
>> @@ -741,8 +743,10 @@ static void mmci_post_request(struct mmc_host *mmc, struct mmc_request *mrq,
>>   static void mmci_get_next_data(struct mmci_host *host, struct mmc_data *data)
>>   {
>>   }
>> -static inline void mmci_dma_setup(struct mmci_host *host)
>> +
>> +static inline int mmci_dma_setup(struct mmci_host *host)
>>   {
>> +       return 0;
>>   }
>>
>>   static inline void mmci_dma_release(struct mmci_host *host)
>> @@ -1796,7 +1800,9 @@ static int mmci_probe(struct amba_device *dev,
>>                   amba_rev(dev), (unsigned long long)dev->res.start,
>>                   dev->irq[0], dev->irq[1]);
>>
>> -       mmci_dma_setup(host);
>> +       ret = mmci_dma_setup(host);
>> +       if (ret)
>> +               goto clk_disable;
>>
>>          pm_runtime_set_autosuspend_delay(&dev->dev, 50);
>>          pm_runtime_use_autosuspend(&dev->dev);
>> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
>> index 21aaf9a..06299ac 100644
>> --- a/drivers/mmc/host/mmci.h
>> +++ b/drivers/mmc/host/mmci.h
>> @@ -273,7 +273,7 @@ struct variant_data {
>>
>>   /* mmci variant callbacks */
>>   struct mmci_host_ops {
>> -       void (*dma_setup)(struct mmci_host *host);
>> +       int (*dma_setup)(struct mmci_host *host);
>>   };
>>
>>   struct mmci_host_next {
>> diff --git a/drivers/mmc/host/mmci_qcom_dml.c b/drivers/mmc/host/mmci_qcom_dml.c
>> index be3fab5..1bb59cf 100644
>> --- a/drivers/mmc/host/mmci_qcom_dml.c
>> +++ b/drivers/mmc/host/mmci_qcom_dml.c
>> @@ -119,7 +119,7 @@ static int of_get_dml_pipe_index(struct device_node *np, const char *name)
>>   }
>>
>>   /* Initialize the dml hardware connected to SD Card controller */
>> -static void qcom_dma_setup(struct mmci_host *host)
>> +static int qcom_dma_setup(struct mmci_host *host)
>>   {
>>          u32 config;
>>          void __iomem *base;
>> @@ -131,7 +131,7 @@ static void qcom_dma_setup(struct mmci_host *host)
>>
>>          if (producer_id < 0 || consumer_id < 0) {
>>                  host->variant->qcom_dml = false;
> 
> It seems like the existing code is an attempt to fallback to use pio
> mode. However, I doubt it works as is.

oops, I seen that like a variant identification issue, so if it's a
fallback to pio mode it doesn't work.

> 
>> -               return;
>> +               return -EINVAL;
> 
> My point is, if you return an error code here, it means that the error
> code becomes propagated and ->probe() will fail.
> 
> Ideally, we should be able fall back to pio mode when dma doesn't
> work. I have looped in Srinivas who implemented the qcom dml support,
> let's see if he can explains the intent with the code.
> 
> I also volunteer to help out running some tests on the 410c platform,
> however allow me a day or two to do that.

yes, I would be more reassured

> 
>>          }
>>
>>          base = host->base + DML_OFFSET;
>> @@ -175,6 +175,8 @@ static void qcom_dma_setup(struct mmci_host *host)
>>
>>          /* Make sure dml initialization is finished */
>>          mb();
>> +
>> +       return 0;
>>   }
>>
>>   static struct mmci_host_ops qcom_variant_ops = {
>> --
>> 2.7.4
>>
> 
> Kind regards
> Uffe
> 