[PATCH net-next 0/2] net: ipa: IPA v4.5 inline checksum offload

[PATCH net-next 0/2] net: ipa: IPA v4.5 inline checksum offload

[Alex Elder]

This series includes one changed destined for a central header file
and a second (dependent on the first) that applies to the IPA driver.
If these should be posted a different way, please let me know.

The first patch introduces a new data structure defining the format
of a header that's used for "inline" checksum offload.  Changes to
the RMNet driver are required to fully support this feature, and
those will be provided separately.

The second patch implements changes to the IPA driver required to
support inline checksum offload for IPA version 4.5.  It uses only
the *size* of the new data structure.

					-Alex

Alex Elder (2):
  if_rmnet.h: define struct rmnet_map_v5_csum_header
  net: ipa: add support for inline checksum offload

 drivers/net/ipa/ipa_endpoint.c | 50 ++++++++++++++++++++++++++--------
 drivers/net/ipa/ipa_reg.h      |  1 +
 include/linux/if_rmnet.h       | 30 ++++++++++++++++++++
 3 files changed, 70 insertions(+), 11 deletions(-)

-- 
2.20.1

[PATCH net-next 1/2] if_rmnet.h: define struct rmnet_map_v5_csum_header

[Alex Elder]

Define a new rmnet_map_v5_csum_header structure type.  It will be
used for inline checksum offload, supported with version 5 of the
QMAP protocol.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 include/linux/if_rmnet.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h
index 9661416a9bb47..0fdda0e6e9963 100644
--- a/include/linux/if_rmnet.h
+++ b/include/linux/if_rmnet.h
@@ -52,4 +52,34 @@ struct rmnet_map_ul_csum_header {
 #endif
 } __aligned(1);
 
+
+/* Values for the header_type field of struct rmnet_map_v5_csum_header */
+enum rmnet_map_v5_header_type {
+	RMNET_MAP_HEADER_TYPE_UNKNOWN		= 0x0,
+	RMNET_MAP_HEADER_TYPE_COALESCING	= 0x1,
+	RMNET_MAP_HEADER_TYPE_CSUM_OFFLOAD	= 0x2,
+};
+
+/* QMAP v5 checksum offload header */
+struct rmnet_map_v5_csum_header {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	u8 next_hdr:1;
+	u8 header_type:7;
+
+	u8 hw_reserved:5;
+	u8 priority:1;
+	u8 hw_reserved_bit:1;
+	u8 csum_valid_required:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	u8 header_type:7;
+	u8 next_hdr:1;
+
+	u8 csum_valid_required:1;
+	u8 hw_reserved_bit:1;
+	u8 priority:1;
+	u8 hw_reserved:5;
+#endif
+	__be16 reserved;
+};
+
 #endif /* !(_LINUX_IF_RMNET_H_) */
-- 
2.20.1

[PATCH net-next 2/2] net: ipa: add support for inline checksum offload

[Alex Elder]

Starting with IPA v4.5, IP payload checksum offload is implemented
differently.

Prior to v4.5, the IPA hardware appends an rmnet_map_dl_csum_trailer
structure to each packet if checksum offload is enabled in the
download direction (modem->AP).  In the upload direction (AP->modem)
a rmnet_map_ul_csum_header structure is prepended before each sent
packet.

Starting with IPA v4.5, checksum offload is implemented using a
single new rmnet_map_v5_csum_header structure which sits between
the QMAP header and the packet data.  The same header structure
is used in both directions.

The new header contains a header type (CSUM_OFFLOAD); a checksum
flag; and a flag indicating whether any other headers follow this
one.  The checksum flag indicates whether the hardware should
compute (and insert) the checksum on a sent packet.  On a received
packet the checksum flag indicates whether the hardware confirms the
checksum value in the payload is correct.

To function, the rmnet driver must also add support for this new
"inline" checksum offload.  The changes implementing this will be
submitted soon.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_endpoint.c | 50 ++++++++++++++++++++++++++--------
 drivers/net/ipa/ipa_reg.h      |  1 +
 2 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index 27f543b6780b1..1a4749f7f03e6 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -434,33 +434,63 @@ int ipa_endpoint_modem_exception_reset_all(struct ipa *ipa)
 static void ipa_endpoint_init_cfg(struct ipa_endpoint *endpoint)
 {
 	u32 offset = IPA_REG_ENDP_INIT_CFG_N_OFFSET(endpoint->endpoint_id);
+	enum ipa_cs_offload_en enabled;
 	u32 val = 0;
 
 	/* FRAG_OFFLOAD_EN is 0 */
 	if (endpoint->data->checksum) {
+		enum ipa_version version = endpoint->ipa->version;
+
 		if (endpoint->toward_ipa) {
 			u32 checksum_offset;
 
-			val |= u32_encode_bits(IPA_CS_OFFLOAD_UL,
-					       CS_OFFLOAD_EN_FMASK);
 			/* Checksum header offset is in 4-byte units */
 			checksum_offset = sizeof(struct rmnet_map_header);
 			checksum_offset /= sizeof(u32);
 			val |= u32_encode_bits(checksum_offset,
 					       CS_METADATA_HDR_OFFSET_FMASK);
+
+			enabled = version < IPA_VERSION_4_5
+					? IPA_CS_OFFLOAD_UL
+					: IPA_CS_OFFLOAD_INLINE;
 		} else {
-			val |= u32_encode_bits(IPA_CS_OFFLOAD_DL,
-					       CS_OFFLOAD_EN_FMASK);
+			enabled = version < IPA_VERSION_4_5
+					? IPA_CS_OFFLOAD_DL
+					: IPA_CS_OFFLOAD_INLINE;
 		}
 	} else {
-		val |= u32_encode_bits(IPA_CS_OFFLOAD_NONE,
-				       CS_OFFLOAD_EN_FMASK);
+		enabled = IPA_CS_OFFLOAD_NONE;
 	}
+	val |= u32_encode_bits(enabled, CS_OFFLOAD_EN_FMASK);
 	/* CS_GEN_QMB_MASTER_SEL is 0 */
 
 	iowrite32(val, endpoint->ipa->reg_virt + offset);
 }
 
+static u32
+ipa_qmap_header_size(enum ipa_version version, struct ipa_endpoint *endpoint)
+{
+	u32 header_size = sizeof(struct rmnet_map_header);
+
+	/* ipa_assert(endpoint->data->qmap); */
+
+	/* We might supply a checksum header after the QMAP header */
+	if (endpoint->data->checksum) {
+		if (version < IPA_VERSION_4_5) {
+			size_t size = sizeof(struct rmnet_map_ul_csum_header);
+
+			/* Checksum header inserted for AP TX endpoints */
+			if (endpoint->toward_ipa)
+				header_size += size;
+		} else {
+			/* Checksum header is used in both directions */
+			header_size += sizeof(struct rmnet_map_v5_csum_header);
+		}
+	}
+
+	return header_size;
+}
+
 /**
  * ipa_endpoint_init_hdr() - Initialize HDR endpoint configuration register
  * @endpoint:	Endpoint pointer
@@ -489,13 +519,11 @@ static void ipa_endpoint_init_hdr(struct ipa_endpoint *endpoint)
 	u32 val = 0;
 
 	if (endpoint->data->qmap) {
-		size_t header_size = sizeof(struct rmnet_map_header);
 		enum ipa_version version = ipa->version;
+		size_t header_size;
 
-		/* We might supply a checksum header after the QMAP header */
-		if (endpoint->toward_ipa && endpoint->data->checksum)
-			header_size += sizeof(struct rmnet_map_ul_csum_header);
-		val |= ipa_header_size_encoded(version, header_size);
+		header_size = ipa_qmap_header_size(version, endpoint);
+		val = ipa_header_size_encoded(version, header_size);
 
 		/* Define how to fill fields in a received QMAP header */
 		if (!endpoint->toward_ipa) {
diff --git a/drivers/net/ipa/ipa_reg.h b/drivers/net/ipa/ipa_reg.h
index 3fabafd7e32c6..6738cafe979ce 100644
--- a/drivers/net/ipa/ipa_reg.h
+++ b/drivers/net/ipa/ipa_reg.h
@@ -356,6 +356,7 @@ enum ipa_cs_offload_en {
 	IPA_CS_OFFLOAD_NONE		= 0x0,
 	IPA_CS_OFFLOAD_UL		= 0x1,
 	IPA_CS_OFFLOAD_DL		= 0x2,
+	IPA_CS_OFFLOAD_INLINE		= 0x1,	/* IPA v4.5 */
 };
 
 #define IPA_REG_ENDP_INIT_HDR_N_OFFSET(ep) \
-- 
2.20.1

Re: [PATCH net-next 2/2] net: ipa: add support for inline checksum offload

[Jakub Kicinski]

On Mon, 30 Nov 2020 18:41:43 -0600 Alex Elder wrote:
> Starting with IPA v4.5, IP payload checksum offload is implemented
> differently.
> 
> Prior to v4.5, the IPA hardware appends an rmnet_map_dl_csum_trailer
> structure to each packet if checksum offload is enabled in the
> download direction (modem->AP).  In the upload direction (AP->modem)
> a rmnet_map_ul_csum_header structure is prepended before each sent
> packet.
> 
> Starting with IPA v4.5, checksum offload is implemented using a
> single new rmnet_map_v5_csum_header structure which sits between
> the QMAP header and the packet data.  The same header structure
> is used in both directions.
> 
> The new header contains a header type (CSUM_OFFLOAD); a checksum
> flag; and a flag indicating whether any other headers follow this
> one.  The checksum flag indicates whether the hardware should
> compute (and insert) the checksum on a sent packet.  On a received
> packet the checksum flag indicates whether the hardware confirms the
> checksum value in the payload is correct.
> 
> To function, the rmnet driver must also add support for this new
> "inline" checksum offload.  The changes implementing this will be
> submitted soon.

We don't usually merge half of a feature. Why not wait until all
support is in place?

Do I understand right that it's rmnet that will push the csum header?
This change seems to only reserve space for it and request the feature
at init..

> diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
> index 27f543b6780b1..1a4749f7f03e6 100644
> --- a/drivers/net/ipa/ipa_endpoint.c
> +++ b/drivers/net/ipa/ipa_endpoint.c
> @@ -434,33 +434,63 @@ int ipa_endpoint_modem_exception_reset_all(struct ipa *ipa)
>  static void ipa_endpoint_init_cfg(struct ipa_endpoint *endpoint)
>  {
>  	u32 offset = IPA_REG_ENDP_INIT_CFG_N_OFFSET(endpoint->endpoint_id);
> +	enum ipa_cs_offload_en enabled;
>  	u32 val = 0;
>  
>  	/* FRAG_OFFLOAD_EN is 0 */
>  	if (endpoint->data->checksum) {
> +		enum ipa_version version = endpoint->ipa->version;
> +
>  		if (endpoint->toward_ipa) {
>  			u32 checksum_offset;
>  
> -			val |= u32_encode_bits(IPA_CS_OFFLOAD_UL,
> -					       CS_OFFLOAD_EN_FMASK);
>  			/* Checksum header offset is in 4-byte units */
>  			checksum_offset = sizeof(struct rmnet_map_header);
>  			checksum_offset /= sizeof(u32);
>  			val |= u32_encode_bits(checksum_offset,
>  					       CS_METADATA_HDR_OFFSET_FMASK);
> +
> +			enabled = version < IPA_VERSION_4_5
> +					? IPA_CS_OFFLOAD_UL
> +					: IPA_CS_OFFLOAD_INLINE;
>  		} else {
> -			val |= u32_encode_bits(IPA_CS_OFFLOAD_DL,
> -					       CS_OFFLOAD_EN_FMASK);
> +			enabled = version < IPA_VERSION_4_5
> +					? IPA_CS_OFFLOAD_DL
> +					: IPA_CS_OFFLOAD_INLINE;
>  		}
>  	} else {
> -		val |= u32_encode_bits(IPA_CS_OFFLOAD_NONE,
> -				       CS_OFFLOAD_EN_FMASK);
> +		enabled = IPA_CS_OFFLOAD_NONE;
>  	}
> +	val |= u32_encode_bits(enabled, CS_OFFLOAD_EN_FMASK);
>  	/* CS_GEN_QMB_MASTER_SEL is 0 */
>  
>  	iowrite32(val, endpoint->ipa->reg_virt + offset);
>  }
>  
> +static u32
> +ipa_qmap_header_size(enum ipa_version version, struct ipa_endpoint *endpoint)
> +{
> +	u32 header_size = sizeof(struct rmnet_map_header);
> +
> +	/* ipa_assert(endpoint->data->qmap); */
> +
> +	/* We might supply a checksum header after the QMAP header */
> +	if (endpoint->data->checksum) {
> +		if (version < IPA_VERSION_4_5) {
> +			size_t size = sizeof(struct rmnet_map_ul_csum_header);
> +
> +			/* Checksum header inserted for AP TX endpoints */
> +			if (endpoint->toward_ipa)
> +				header_size += size;
> +		} else {
> +			/* Checksum header is used in both directions */
> +			header_size += sizeof(struct rmnet_map_v5_csum_header);
> +		}
> +	}
> +
> +	return header_size;
> +}

Re: [PATCH net-next 2/2] net: ipa: add support for inline checksum offload

[Alex Elder]

On 12/1/20 8:13 PM, Jakub Kicinski wrote:
>> To function, the rmnet driver must also add support for this new
>> "inline" checksum offload.  The changes implementing this will be
>> submitted soon.
> We don't usually merge half of a feature. Why not wait until all
> support is in place?
> 
> Do I understand right that it's rmnet that will push the csum header?
> This change seems to only reserve space for it and request the feature
> at init..

You are correct.  The IPA hardware needs to be programmed to
perform the computation and verify that the checksum in the
header matches what it computes (for AP RX offload), or
insert it into the header (for AP TX offload).  That's what
this patch handles.

The RMNet driver is responsible for stripping the offload
header off on RX, and acting on what it says (i.e., whether
hardware is able to state the checksum is good).  And on TX
it inserts an offload header that says what to checksum and
where to put it in the packet.

It's totally fine not to merge this until we have the whole
package ready, I understand.  I'll see what I can do to get
that done quickly.

Thanks Jakub.

					-Alex