[PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no arguments

[PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no arguments

[Ekansh Gupta]

The FDs for DMA handles to be freed is updated in fdlist by DSP over
a remote call. This holds true even for remote calls with no
arguments. To handle this, get_args and put_args are needed to
be called for remote calls with no arguments also as fdlist
is allocated in get_args and FDs updated in fdlist is freed
in put_args.

Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
---
 drivers/misc/fastrpc.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 9666d28..e6df66e 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1153,11 +1153,9 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
 
-	if (ctx->nscalars) {
-		err = fastrpc_get_args(kernel, ctx);
-		if (err)
-			goto bail;
-	}
+	err = fastrpc_get_args(kernel, ctx);
+	if (err)
+		goto bail;
 
 	/* make sure that all CPU memory writes are seen by DSP */
 	dma_wmb();
@@ -1181,14 +1179,12 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
 	if (err)
 		goto bail;
 
-	if (ctx->nscalars) {
-		/* make sure that all memory writes by DSP are seen by CPU */
-		dma_rmb();
-		/* populate all the output buffers with results */
-		err = fastrpc_put_args(ctx, kernel);
-		if (err)
-			goto bail;
-	}
+	/* make sure that all memory writes by DSP are seen by CPU */
+	dma_rmb();
+	/* populate all the output buffers with results */
+	err = fastrpc_put_args(ctx, kernel);
+	if (err)
+		goto bail;
 
 bail:
 	if (err != -ERESTARTSYS && err != -ETIMEDOUT) {
-- 
2.7.4

Re: [PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no arguments

[Srinivas Kandagatla]

Thanks Ekansh for this patch.

few comments below

On 31/08/2023 07:23, Ekansh Gupta wrote:
> The FDs for DMA handles to be freed is updated in fdlist by DSP over

So the dsp is updating the fd list after invoke?


> a remote call. This holds true even for remote calls with no
> arguments. To handle this, get_args and put_args are needed to
> be called for remote calls with no arguments also as fdlist
> is allocated in get_args and FDs updated in fdlist is freed
> in put_args.
> 
> Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
> ---
>   drivers/misc/fastrpc.c | 22 +++++++++-------------
>   1 file changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 9666d28..e6df66e 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1153,11 +1153,9 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
>   	if (IS_ERR(ctx))
>   		return PTR_ERR(ctx);
>   
> -	if (ctx->nscalars) {

Why do we need to remove this check?
fastrpc_internal_invoke will have nscalars set before calling. and we 
are not dealing with fdlist in fastrpc_get_args(), so am not sure what 
this change is helping with.


> -		err = fastrpc_get_args(kernel, ctx);
> -		if (err)
> -			goto bail;
> -	}
> +	err = fastrpc_get_args(kernel, ctx);
> +	if (err)
> +		goto bail;
>   
>   	/* make sure that all CPU memory writes are seen by DSP */
>   	dma_wmb();
> @@ -1181,14 +1179,12 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
>   	if (err)
>   		goto bail;
>   
> -	if (ctx->nscalars) {
> -		/* make sure that all memory writes by DSP are seen by CPU */
> -		dma_rmb();
> -		/* populate all the output buffers with results */
> -		err = fastrpc_put_args(ctx, kernel);
> -		if (err)
> -			goto bail;
> -	}
> +	/* make sure that all memory writes by DSP are seen by CPU */
> +	dma_rmb();
> +	/* populate all the output buffers with results */

A comment about fdlist here would be really useful

> +	err = fastrpc_put_args(ctx, kernel);
> +	if (err)
> +		goto bail;
>   
>   bail:
>   	if (err != -ERESTARTSYS && err != -ETIMEDOUT) {

Re: [PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no arguments

[Ekansh Gupta]

On 9/26/2023 3:57 PM, Srinivas Kandagatla wrote:
> Thanks Ekansh for this patch.
> 
> few comments below
> 
> On 31/08/2023 07:23, Ekansh Gupta wrote:
>> The FDs for DMA handles to be freed is updated in fdlist by DSP over
> 
> So the dsp is updating the fd list after invoke?
> 
Yes, correct. DSP updates this fd list when the buffer is no longer 
needed by the user PD.
> 
>> a remote call. This holds true even for remote calls with no
>> arguments. To handle this, get_args and put_args are needed to
>> be called for remote calls with no arguments also as fdlist
>> is allocated in get_args and FDs updated in fdlist is freed
>> in put_args.
>>
>> Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
>> ---
>>   drivers/misc/fastrpc.c | 22 +++++++++-------------
>>   1 file changed, 9 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index 9666d28..e6df66e 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -1153,11 +1153,9 @@ static int fastrpc_internal_invoke(struct 
>> fastrpc_user *fl,  u32 kernel,
>>       if (IS_ERR(ctx))
>>           return PTR_ERR(ctx);
>> -    if (ctx->nscalars) {
> 
> Why do we need to remove this check?
> fastrpc_internal_invoke will have nscalars set before calling. and we 
> are not dealing with fdlist in fastrpc_get_args(), so am not sure what 
> this change is helping with.
Memory for fdlist is allocated as part of fastrpc_get_args. The reason 
to add this change is that fdlist can be updated by DSP over a call with 
no remote arguments, for this call, there should be some fdlist 
allocated so the DSP can update the list if needed. Same apply for 
fastrpc_put_args also as when DSP updates fdlist for any remote call 
with no arguments, the maps corresponding to the fdlist should be freed.
> 
> 
>> -        err = fastrpc_get_args(kernel, ctx);
>> -        if (err)
>> -            goto bail;
>> -    }
>> +    err = fastrpc_get_args(kernel, ctx);
>> +    if (err)
>> +        goto bail;
>>       /* make sure that all CPU memory writes are seen by DSP */
>>       dma_wmb();
>> @@ -1181,14 +1179,12 @@ static int fastrpc_internal_invoke(struct 
>> fastrpc_user *fl,  u32 kernel,
>>       if (err)
>>           goto bail;
>> -    if (ctx->nscalars) {
>> -        /* make sure that all memory writes by DSP are seen by CPU */
>> -        dma_rmb();
>> -        /* populate all the output buffers with results */
>> -        err = fastrpc_put_args(ctx, kernel);
>> -        if (err)
>> -            goto bail;
>> -    }
>> +    /* make sure that all memory writes by DSP are seen by CPU */
>> +    dma_rmb();
>> +    /* populate all the output buffers with results */
> 
> A comment about fdlist here would be really useful
Sure, I will add a comment in the next patch. Do you suggest to add 
comment here or inside fastrpc_put_args function:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/misc/fastrpc.c#n1092
> 
>> +    err = fastrpc_put_args(ctx, kernel);
>> +    if (err)
>> +        goto bail;
>>   bail:
>>       if (err != -ERESTARTSYS && err != -ETIMEDOUT) {

Re: [PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no arguments

[Greg KH]

On Thu, Aug 31, 2023 at 11:53:49AM +0530, Ekansh Gupta wrote:
> The FDs for DMA handles to be freed is updated in fdlist by DSP over
> a remote call. This holds true even for remote calls with no
> arguments. To handle this, get_args and put_args are needed to
> be called for remote calls with no arguments also as fdlist
> is allocated in get_args and FDs updated in fdlist is freed
> in put_args.
> 
> Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>

What commit id does this fix?  Or is this new functionality?

thanks,

greg k-h

Re: [PATCH v1] misc: fastrpc: Free DMA handles for RPC calls with no arguments

[Ekansh Gupta]

On 9/28/2023 6:35 PM, Greg KH wrote:
> On Thu, Aug 31, 2023 at 11:53:49AM +0530, Ekansh Gupta wrote:
>> The FDs for DMA handles to be freed is updated in fdlist by DSP over
>> a remote call. This holds true even for remote calls with no
>> arguments. To handle this, get_args and put_args are needed to
>> be called for remote calls with no arguments also as fdlist
>> is allocated in get_args and FDs updated in fdlist is freed
>> in put_args.
>>
>> Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
> 
> What commit id does this fix?  Or is this new functionality?
> 
I'll update the details in the next patch.

-ekansh
> thanks,
> 
> greg k-h