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[PATCH v1 2/3] misc: fastrpc: Update context ID mask for polling mode support

Ekansh Gupta posted 3 patches 1 month ago
[PATCH v1 2/3] misc: fastrpc: Update context ID mask for polling mode support
Posted by Ekansh Gupta 1 month ago 
Current fastrpc message context uses a 12-bit mask where the upper
8 bits are context ID from idr_alloc_cyclic and the lower 4 bits
represent PD type. This design works for normal fastrpc calls but
doesn't work as expected for polling mode. To enable polling mode
support from DSP(DSP writes to poll memory), DSP expects a 16-bit
context where the upper 8 bits are context ID, the lower 4 bits are
PD type and the 5th bit from the end denotes async mode(not yet
upstreamed). If this bit is set, DSP disables polling. With the
current design, odd context IDs set this bit, causing DSP to skip
poll memory updates. Update the context mask to ensure a hole
which won't get populated, ensuring polling mode works as expected.

Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
---
 drivers/misc/fastrpc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 0991ac487192..57e118de6e4a 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -37,7 +37,7 @@
 #define FASTRPC_CTX_MAX (256)
 #define FASTRPC_INIT_HANDLE	1
 #define FASTRPC_DSP_UTILITIES_HANDLE	2
-#define FASTRPC_CTXID_MASK (0xFF0)
+#define FASTRPC_CTXID_MASK (0xFF00)
 #define INIT_FILELEN_MAX (2 * 1024 * 1024)
 #define INIT_FILE_NAMELEN_MAX (128)
 #define FASTRPC_DEVICE_NAME	"fastrpc"
@@ -487,7 +487,7 @@ static void fastrpc_context_free(struct kref *ref)
 		fastrpc_buf_free(ctx->buf);
 
 	spin_lock_irqsave(&cctx->lock, flags);
-	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 4);
+	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 8);
 	spin_unlock_irqrestore(&cctx->lock, flags);
 
 	kfree(ctx->maps);
@@ -623,7 +623,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(
 		spin_unlock_irqrestore(&cctx->lock, flags);
 		goto err_idr;
 	}
-	ctx->ctxid = ret << 4;
+	ctx->ctxid = ret << 8;
 	spin_unlock_irqrestore(&cctx->lock, flags);
 
 	kref_init(&ctx->refcount);
@@ -2449,7 +2449,7 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
 	if (len < sizeof(*rsp))
 		return -EINVAL;
 
-	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 4);
+	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 8);
 
 	spin_lock_irqsave(&cctx->lock, flags);
 	ctx = idr_find(&cctx->ctx_idr, ctxid);
-- 
2.34.1
Re: [PATCH v1 2/3] misc: fastrpc: Update context ID mask for polling mode support
Posted by Dmitry Baryshkov 1 month ago 
On Mon, Sep 01, 2025 at 11:03:35AM +0530, Ekansh Gupta wrote:
> Current fastrpc message context uses a 12-bit mask where the upper
> 8 bits are context ID from idr_alloc_cyclic and the lower 4 bits
> represent PD type. This design works for normal fastrpc calls but

FastRPC (here and in several other places).

> doesn't work as expected for polling mode. To enable polling mode
> support from DSP(DSP writes to poll memory), DSP expects a 16-bit
> context where the upper 8 bits are context ID, the lower 4 bits are
> PD type and the 5th bit from the end denotes async mode(not yet
> upstreamed). If this bit is set, DSP disables polling. With the
> current design, odd context IDs set this bit, causing DSP to skip
> poll memory updates.

This looks like a description of a bugfix. In such a case, move it to
the start of the series, add necessary tatgs and change commit message
accordingly.

> Update the context mask to ensure a hole
> which won't get populated, ensuring polling mode works as expected.
> 
> Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
> ---
>  drivers/misc/fastrpc.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 0991ac487192..57e118de6e4a 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -37,7 +37,7 @@
>  #define FASTRPC_CTX_MAX (256)
>  #define FASTRPC_INIT_HANDLE	1
>  #define FASTRPC_DSP_UTILITIES_HANDLE	2
> -#define FASTRPC_CTXID_MASK (0xFF0)
> +#define FASTRPC_CTXID_MASK (0xFF00)
>  #define INIT_FILELEN_MAX (2 * 1024 * 1024)
>  #define INIT_FILE_NAMELEN_MAX (128)
>  #define FASTRPC_DEVICE_NAME	"fastrpc"
> @@ -487,7 +487,7 @@ static void fastrpc_context_free(struct kref *ref)
>  		fastrpc_buf_free(ctx->buf);
>  
>  	spin_lock_irqsave(&cctx->lock, flags);
> -	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 4);
> +	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 8);

#define magic value

>  	spin_unlock_irqrestore(&cctx->lock, flags);
>  
>  	kfree(ctx->maps);
> @@ -623,7 +623,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(
>  		spin_unlock_irqrestore(&cctx->lock, flags);
>  		goto err_idr;
>  	}
> -	ctx->ctxid = ret << 4;
> +	ctx->ctxid = ret << 8;
>  	spin_unlock_irqrestore(&cctx->lock, flags);
>  
>  	kref_init(&ctx->refcount);
> @@ -2449,7 +2449,7 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
>  	if (len < sizeof(*rsp))
>  		return -EINVAL;
>  
> -	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 4);
> +	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 8);
>  
>  	spin_lock_irqsave(&cctx->lock, flags);
>  	ctx = idr_find(&cctx->ctx_idr, ctxid);
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry
Re: [PATCH v1 2/3] misc: fastrpc: Update context ID mask for polling mode support
Posted by Ekansh Gupta 3 weeks, 4 days ago 

On 9/2/2025 9:42 AM, Dmitry Baryshkov wrote:
> On Mon, Sep 01, 2025 at 11:03:35AM +0530, Ekansh Gupta wrote:
>> Current fastrpc message context uses a 12-bit mask where the upper
>> 8 bits are context ID from idr_alloc_cyclic and the lower 4 bits
>> represent PD type. This design works for normal fastrpc calls but
> FastRPC (here and in several other places).
Ack.
>
>> doesn't work as expected for polling mode. To enable polling mode
>> support from DSP(DSP writes to poll memory), DSP expects a 16-bit
>> context where the upper 8 bits are context ID, the lower 4 bits are
>> PD type and the 5th bit from the end denotes async mode(not yet
>> upstreamed). If this bit is set, DSP disables polling. With the
>> current design, odd context IDs set this bit, causing DSP to skip
>> poll memory updates.
> This looks like a description of a bugfix. In such a case, move it to
> the start of the series, add necessary tatgs and change commit message
> accordingly.
I'm not sure if it could be called a bug fix as there is no problem with existing mask.
The problem is seen only when polling mode is added.
>
>> Update the context mask to ensure a hole
>> which won't get populated, ensuring polling mode works as expected.
>>
>> Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
>> ---
>>  drivers/misc/fastrpc.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index 0991ac487192..57e118de6e4a 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -37,7 +37,7 @@
>>  #define FASTRPC_CTX_MAX (256)
>>  #define FASTRPC_INIT_HANDLE	1
>>  #define FASTRPC_DSP_UTILITIES_HANDLE	2
>> -#define FASTRPC_CTXID_MASK (0xFF0)
>> +#define FASTRPC_CTXID_MASK (0xFF00)
>>  #define INIT_FILELEN_MAX (2 * 1024 * 1024)
>>  #define INIT_FILE_NAMELEN_MAX (128)
>>  #define FASTRPC_DEVICE_NAME	"fastrpc"
>> @@ -487,7 +487,7 @@ static void fastrpc_context_free(struct kref *ref)
>>  		fastrpc_buf_free(ctx->buf);
>>  
>>  	spin_lock_irqsave(&cctx->lock, flags);
>> -	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 4);
>> +	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 8);
> #define magic value
Ack.
>
>>  	spin_unlock_irqrestore(&cctx->lock, flags);
>>  
>>  	kfree(ctx->maps);
>> @@ -623,7 +623,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(
>>  		spin_unlock_irqrestore(&cctx->lock, flags);
>>  		goto err_idr;
>>  	}
>> -	ctx->ctxid = ret << 4;
>> +	ctx->ctxid = ret << 8;
>>  	spin_unlock_irqrestore(&cctx->lock, flags);
>>  
>>  	kref_init(&ctx->refcount);
>> @@ -2449,7 +2449,7 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
>>  	if (len < sizeof(*rsp))
>>  		return -EINVAL;
>>  
>> -	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 4);
>> +	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 8);
>>  
>>  	spin_lock_irqsave(&cctx->lock, flags);
>>  	ctx = idr_find(&cctx->ctx_idr, ctxid);
>> -- 
>> 2.34.1
>>
Re: [PATCH v1 2/3] misc: fastrpc: Update context ID mask for polling mode support
Posted by Dmitry Baryshkov 3 weeks, 4 days ago 
On Mon, Sep 08, 2025 at 10:42:10AM +0530, Ekansh Gupta wrote:
> 
> 
> On 9/2/2025 9:42 AM, Dmitry Baryshkov wrote:
> > On Mon, Sep 01, 2025 at 11:03:35AM +0530, Ekansh Gupta wrote:
> >> Current fastrpc message context uses a 12-bit mask where the upper
> >> 8 bits are context ID from idr_alloc_cyclic and the lower 4 bits
> >> represent PD type. This design works for normal fastrpc calls but
> > FastRPC (here and in several other places).
> Ack.
> >
> >> doesn't work as expected for polling mode. To enable polling mode
> >> support from DSP(DSP writes to poll memory), DSP expects a 16-bit
> >> context where the upper 8 bits are context ID, the lower 4 bits are
> >> PD type and the 5th bit from the end denotes async mode(not yet
> >> upstreamed). If this bit is set, DSP disables polling. With the
> >> current design, odd context IDs set this bit, causing DSP to skip
> >> poll memory updates.
> > This looks like a description of a bugfix. In such a case, move it to
> > the start of the series, add necessary tatgs and change commit message
> > accordingly.
> I'm not sure if it could be called a bug fix as there is no problem with existing mask.
> The problem is seen only when polling mode is added.

This sounds like a perfect part of the commit message.

> >
> >> Update the context mask to ensure a hole
> >> which won't get populated, ensuring polling mode works as expected.
> >>
> >> Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
> >> ---
> >>  drivers/misc/fastrpc.c | 8 ++++----
> >>  1 file changed, 4 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> >> index 0991ac487192..57e118de6e4a 100644
> >> --- a/drivers/misc/fastrpc.c
> >> +++ b/drivers/misc/fastrpc.c
> >> @@ -37,7 +37,7 @@
> >>  #define FASTRPC_CTX_MAX (256)
> >>  #define FASTRPC_INIT_HANDLE	1
> >>  #define FASTRPC_DSP_UTILITIES_HANDLE	2
> >> -#define FASTRPC_CTXID_MASK (0xFF0)
> >> +#define FASTRPC_CTXID_MASK (0xFF00)
> >>  #define INIT_FILELEN_MAX (2 * 1024 * 1024)
> >>  #define INIT_FILE_NAMELEN_MAX (128)
> >>  #define FASTRPC_DEVICE_NAME	"fastrpc"
> >> @@ -487,7 +487,7 @@ static void fastrpc_context_free(struct kref *ref)
> >>  		fastrpc_buf_free(ctx->buf);
> >>  
> >>  	spin_lock_irqsave(&cctx->lock, flags);
> >> -	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 4);
> >> +	idr_remove(&cctx->ctx_idr, ctx->ctxid >> 8);
> > #define magic value
> Ack.
> >
> >>  	spin_unlock_irqrestore(&cctx->lock, flags);
> >>  
> >>  	kfree(ctx->maps);
> >> @@ -623,7 +623,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(
> >>  		spin_unlock_irqrestore(&cctx->lock, flags);
> >>  		goto err_idr;
> >>  	}
> >> -	ctx->ctxid = ret << 4;
> >> +	ctx->ctxid = ret << 8;
> >>  	spin_unlock_irqrestore(&cctx->lock, flags);
> >>  
> >>  	kref_init(&ctx->refcount);
> >> @@ -2449,7 +2449,7 @@ static int fastrpc_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
> >>  	if (len < sizeof(*rsp))
> >>  		return -EINVAL;
> >>  
> >> -	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 4);
> >> +	ctxid = ((rsp->ctx & FASTRPC_CTXID_MASK) >> 8);
> >>  
> >>  	spin_lock_irqsave(&cctx->lock, flags);
> >>  	ctx = idr_find(&cctx->ctx_idr, ctxid);
> >> -- 
> >> 2.34.1
> >>
> 

-- 
With best wishes
Dmitry

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