[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Srinivas Kandagatla]

On 16/01/18 19:38, Sagar Dharia wrote:
> 
> On 1/16/2018 12:02 PM, srinivas.kandagatla@linaro.org wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>>
>> When BAM is remotely controlled it does not sound correct to control
>> its clk on Linux side. Make it optional, so that its not madatory
>> for remote controlled BAM instances.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> ---
>>   drivers/dma/qcom/bam_dma.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
>> index 03c4eb3fd314..78e488e8f96d 100644
>> --- a/drivers/dma/qcom/bam_dma.c
>> +++ b/drivers/dma/qcom/bam_dma.c
>> @@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct 
>> platform_device *pdev)
>>                           "qcom,controlled-remotely");
>>       bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
>> -    if (IS_ERR(bdev->bamclk))
>> -        return PTR_ERR(bdev->bamclk);
>> -
>> -    ret = clk_prepare_enable(bdev->bamclk);
>> -    if (ret) {
>> -        dev_err(bdev->dev, "failed to prepare/enable clock\n");
>> -        return ret;
>> +    if (IS_ERR(bdev->bamclk)) {
>> +        bdev->bamclk = NULL;
>> +    } else {
>> +        ret = clk_prepare_enable(bdev->bamclk);
>> +        if (ret) {
>> +            dev_err(bdev->dev, "failed to prepare/enable clock\n");
>> +            return ret;
>> +        }
> I believe you can also keep pm_runtime disabled if BAM is remotely 
> controlled.

Yes, that's another topic which should be fixed too. I will add that 
patch in next version.

thanks,
srini
> 
> Thanks
> Sagar
>>       }
>>       ret = bam_init(bdev);
>
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[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Srinivas Kandagatla]

On 23/01/18 09:19, Vinod Koul wrote:
> On Mon, Jan 22, 2018 at 09:55:01AM +0000, Srinivas Kandagatla wrote:
> 
>>>> @@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
>>>>   						"qcom,controlled-remotely");
>>>>   	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
>>>
>>> but you still do clk_get unconditionally?
>>
>> Only reason to do this way is to not break existing users in the mainline.
>>
>> remotely controlled BAM is already supported in upstream driver, there are
>> users of this who pass clk from device tree, If I make this conditional then
>> subsequent reads to the BAM registers for those instances might crash the
>> system.
> 
> But these instances are remote controlled, so if we stop representing them
> in Linux, why would we read them?

Plan is that we would transition those users once we get these 
bindings/changes in. Currently I don't have access to any of those 
devices so I made the changes safe, such that it does not break devices 
on mainline.

--srini

>
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[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Vinod Koul]

On Mon, Jan 22, 2018 at 09:55:01AM +0000, Srinivas Kandagatla wrote:

> >>@@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
> >>  						"qcom,controlled-remotely");
> >>  	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
> >
> >but you still do clk_get unconditionally?
> 
> Only reason to do this way is to not break existing users in the mainline.
> 
> remotely controlled BAM is already supported in upstream driver, there are
> users of this who pass clk from device tree, If I make this conditional then
> subsequent reads to the BAM registers for those instances might crash the
> system.

But these instances are remote controlled, so if we stop representing them
in Linux, why would we read them?

[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Srinivas Kandagatla]

On 19/01/18 05:52, Vinod Koul wrote:
> On Tue, Jan 16, 2018 at 07:02:33PM +0000, srinivas.kandagatla@linaro.org wrote:
>> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>>
>> When BAM is remotely controlled it does not sound correct to control
>> its clk on Linux side. Make it optional, so that its not madatory
> 
> s/madatory/mandatory
> 
Yep,
>> for remote controlled BAM instances.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> ---
>>   drivers/dma/qcom/bam_dma.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
>> index 03c4eb3fd314..78e488e8f96d 100644
>> --- a/drivers/dma/qcom/bam_dma.c
>> +++ b/drivers/dma/qcom/bam_dma.c
>> @@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
>>   						"qcom,controlled-remotely");
>>   
>>   	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
> 
> but you still do clk_get unconditionally?

Only reason to do this way is to not break existing users in the mainline.

remotely controlled BAM is already supported in upstream driver, there 
are users of this who pass clk from device tree, If I make this 
conditional then subsequent reads to the BAM registers for those 
instances might crash the system.

This sounds wrong to control clk from linux for the dma controller which 
is remotely controlled. These users should be transitioned to new 
bindings once the new bindings endup in the mainline.

> 
>> -	if (IS_ERR(bdev->bamclk))
>> -		return PTR_ERR(bdev->bamclk);
>> -
>> -	ret = clk_prepare_enable(bdev->bamclk);
>> -	if (ret) {
>> -		dev_err(bdev->dev, "failed to prepare/enable clock\n");
>> -		return ret;
>> +	if (IS_ERR(bdev->bamclk)) {
>> +		bdev->bamclk = NULL;
>> +	} else {
>> +		ret = clk_prepare_enable(bdev->bamclk);
>> +		if (ret) {
>> +			dev_err(bdev->dev, "failed to prepare/enable clock\n");
>> +			return ret;
>> +		}
> 
> wouldn't it be better to set that an instance is remote controlled and thus
> not at all visible to Linux?

We already have a flag "controlled_remotely" for that in the driver.

thanks,
srini
> 
>>   	}
>>   
>>   	ret = bam_init(bdev);
>> -- 
>> 2.15.1
>>
>> --
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>
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[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Vinod Koul]

On Tue, Jan 16, 2018 at 07:02:33PM +0000, srinivas.kandagatla@linaro.org wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> 
> When BAM is remotely controlled it does not sound correct to control
> its clk on Linux side. Make it optional, so that its not madatory

s/madatory/mandatory

> for remote controlled BAM instances.
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>  drivers/dma/qcom/bam_dma.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 03c4eb3fd314..78e488e8f96d 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
>  						"qcom,controlled-remotely");
>  
>  	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");

but you still do clk_get unconditionally?

> -	if (IS_ERR(bdev->bamclk))
> -		return PTR_ERR(bdev->bamclk);
> -
> -	ret = clk_prepare_enable(bdev->bamclk);
> -	if (ret) {
> -		dev_err(bdev->dev, "failed to prepare/enable clock\n");
> -		return ret;
> +	if (IS_ERR(bdev->bamclk)) {
> +		bdev->bamclk = NULL;
> +	} else {
> +		ret = clk_prepare_enable(bdev->bamclk);
> +		if (ret) {
> +			dev_err(bdev->dev, "failed to prepare/enable clock\n");
> +			return ret;
> +		}

wouldn't it be better to set that an instance is remote controlled and thus
not at all visible to Linux?

>  	}
>  
>  	ret = bam_init(bdev);
> -- 
> 2.15.1
> 
> --
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[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Sagar Dharia]

On 1/16/2018 12:02 PM, srinivas.kandagatla@linaro.org wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>
> When BAM is remotely controlled it does not sound correct to control
> its clk on Linux side. Make it optional, so that its not madatory
> for remote controlled BAM instances.
>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>   drivers/dma/qcom/bam_dma.c | 15 ++++++++-------
>   1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 03c4eb3fd314..78e488e8f96d 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
>   						"qcom,controlled-remotely");
>   
>   	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
> -	if (IS_ERR(bdev->bamclk))
> -		return PTR_ERR(bdev->bamclk);
> -
> -	ret = clk_prepare_enable(bdev->bamclk);
> -	if (ret) {
> -		dev_err(bdev->dev, "failed to prepare/enable clock\n");
> -		return ret;
> +	if (IS_ERR(bdev->bamclk)) {
> +		bdev->bamclk = NULL;
> +	} else {
> +		ret = clk_prepare_enable(bdev->bamclk);
> +		if (ret) {
> +			dev_err(bdev->dev, "failed to prepare/enable clock\n");
> +			return ret;
> +		}
I believe you can also keep pm_runtime disabled if BAM is remotely 
controlled.

Thanks
Sagar
>   	}
>   
>   	ret = bam_init(bdev);
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[1/4] dmaengine: qcom: bam_dma: make bam clk optional

[Srinivas Kandagatla]

From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

When BAM is remotely controlled it does not sound correct to control
its clk on Linux side. Make it optional, so that its not madatory
for remote controlled BAM instances.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/dma/qcom/bam_dma.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index 03c4eb3fd314..78e488e8f96d 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
 						"qcom,controlled-remotely");
 
 	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
-	if (IS_ERR(bdev->bamclk))
-		return PTR_ERR(bdev->bamclk);
-
-	ret = clk_prepare_enable(bdev->bamclk);
-	if (ret) {
-		dev_err(bdev->dev, "failed to prepare/enable clock\n");
-		return ret;
+	if (IS_ERR(bdev->bamclk)) {
+		bdev->bamclk = NULL;
+	} else {
+		ret = clk_prepare_enable(bdev->bamclk);
+		if (ret) {
+			dev_err(bdev->dev, "failed to prepare/enable clock\n");
+			return ret;
+		}
 	}
 
 	ret = bam_init(bdev);