[PATCH net-next 3/7] net: ipa: no more global filtering starting with IPA v5.0

From: Alex Elder
Date: Thu Oct 27 2022 - 08:26:58 EST


IPA v5.0 eliminates the global filter table entry. As a result,
there is no need to shift the filtered endpoint bitmap when it is
written to IPA local memory.

Update comments to explain this. Also delete a redundant block of
comments above the function.

Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
---
drivers/net/ipa/ipa_table.c | 59 ++++++++++++++++++++++---------------
1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c
index db1992eaafaa9..cf3a3de239dc3 100644
--- a/drivers/net/ipa/ipa_table.c
+++ b/drivers/net/ipa/ipa_table.c
@@ -32,8 +32,8 @@
* endian 64-bit "slot" that holds the address of a rule definition. (The
* size of these slots is 64 bits regardless of the host DMA address size.)
*
- * Separate tables (both filter and route) used for IPv4 and IPv6. There
- * are normally another set of "hashed" filter and route tables, which are
+ * Separate tables (both filter and route) are used for IPv4 and IPv6. There
+ * is normally another set of "hashed" filter and route tables, which are
* used with a hash of message metadata. Hashed operation is not supported
* by all IPA hardware (IPA v4.2 doesn't support hashed tables).
*
@@ -51,19 +51,32 @@
* Each filter rule is associated with an AP or modem TX endpoint, though
* not all TX endpoints support filtering. The first 64-bit slot in a
* filter table is a bitmap indicating which endpoints have entries in
- * the table. The low-order bit (bit 0) in this bitmap represents a
- * special global filter, which applies to all traffic. This is not
- * used in the current code. Bit 1, if set, indicates that there is an
- * entry (i.e. slot containing a system address referring to a rule) for
- * endpoint 0 in the table. Bit 3, if set, indicates there is an entry
- * for endpoint 2, and so on. Space is set aside in IPA local memory to
- * hold as many filter table entries as might be required, but typically
- * they are not all used.
+ * the table. Each set bit in this bitmap indicates the presence of the
+ * address of a filter rule in the memory following the bitmap. Until IPA
+ * v5.0, the low-order bit (bit 0) in this bitmap represents a special
+ * global filter, which applies to all traffic. Otherwise the position of
+ * each set bit represents an endpoint for which a filter rule is defined.
+ *
+ * The global rule is not used in current code, and support for it is
+ * removed starting at IPA v5.0. For IPA v5.0+, the endpoint bitmap
+ * position defines the endpoint ID--i.e. if bit 1 is set in the endpoint
+ * bitmap, endpoint 1 has a filter rule. Older versions of IPA represent
+ * the presence of a filter rule for endpoint X by bit (X + 1) being set.
+ * I.e., bit 1 set indicates the presence of a filter rule for endpoint 0,
+ * and bit 3 set means there is a filter rule present for endpoint 2.
+ *
+ * Each filter table entry has the address of a set of equations that
+ * implement a filter rule. So following the endpoint bitmap there
+ * will be such an address/entry for each endpoint with a set bit in
+ * the bitmap.
*
* The AP initializes all entries in a filter table to refer to a "zero"
- * entry. Once initialized the modem and AP update the entries for
- * endpoints they "own" directly. Currently the AP does not use the
- * IPA filtering functionality.
+ * rule. Once initialized, the modem and AP update the entries for
+ * endpoints they "own" directly. Currently the AP does not use the IPA
+ * filtering functionality.
+ *
+ * This diagram shows an example of a filter table with an endpoint
+ * bitmap as defined prior to IPA v5.0.
*
* IPA Filter Table
* ----------------------
@@ -658,12 +671,6 @@ bool ipa_table_mem_valid(struct ipa *ipa, bool filter)
* when a route table is initialized or reset, its entries are made to refer
* to the zero rule. The zero rule is shared for route and filter tables.
*
- * Note that the IPA hardware requires a filter or route rule address to be
- * aligned on a 128 byte boundary. The coherent DMA buffer we allocate here
- * has a minimum alignment, and we place the zero rule at the base of that
- * allocated space. In ipa_table_init() we verify the minimum DMA allocation
- * meets our requirement.
- *
* +-------------------+
* --> | zero rule |
* / |-------------------|
@@ -708,12 +715,16 @@ int ipa_table_init(struct ipa *ipa)
/* First slot is the zero rule */
*virt++ = 0;

- /* Next is the filter table bitmap. The "soft" bitmap value
- * must be converted to the hardware representation by shifting
- * it left one position. (Bit 0 repesents global filtering,
- * which is possible but not used.)
+ /* Next is the filter table bitmap. The "soft" bitmap value might
+ * need to be converted to the hardware representation by shifting
+ * it left one position. Prior to IPA v5.0, bit 0 repesents global
+ * filtering, which is possible but not used. IPA v5.0+ eliminated
+ * that option, so there's no shifting required.
*/
- *virt++ = cpu_to_le64((u64)ipa->filter_map << 1);
+ if (ipa->version < IPA_VERSION_5_0)
+ *virt++ = cpu_to_le64((u64)ipa->filter_map << 1);
+ else
+ *virt++ = cpu_to_le64((u64)ipa->filter_map);

/* All the rest contain the DMA address of the zero rule */
le_addr = cpu_to_le64(addr);
--
2.34.1