net: ipa: implement MAX_READS_BEATS QSB data

Starting with IPA v4.0, a limit is placed on the number of bytes
outstanding in a transaction, to reduce latency.  The limit is
imposed only if this value is non-zero.

We don't use a non-zero value for SC7180, but newer versions of IPA
do.  Prepare for that by allowing a programmed value to be specified
in the platform configuration data.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ipa/ipa_data-sc7180.c

@@ -14,6 +14,7 @@ static const struct ipa_qsb_data ipa_qsb_data[] = {
 	[IPA_QSB_MASTER_DDR] = {
 		.max_writes	= 8,
 		.max_reads	= 12,
+		/* no outstanding read byte (beat) limit */
 	},
 };
 

drivers/net/ipa/ipa_data.h

@@ -59,10 +59,12 @@ enum ipa_qsb_master_id {
  * struct ipa_qsb_data - Qualcomm System Bus configuration data
  * @max_writes:	Maximum outstanding write requests for this master
  * @max_reads:	Maximum outstanding read requests for this master
+ * @max_reads_beats: Max outstanding read bytes in 8-byte "beats" (if non-zero)
  */
 struct ipa_qsb_data {
 	u8 max_writes;
 	u8 max_reads;
+	u8 max_reads_beats;		/* Not present for IPA v3.5.1 */
 };
 
 /**

drivers/net/ipa/ipa_main.c

@@ -274,10 +274,16 @@ ipa_hardware_config_qsb(struct ipa *ipa, const struct ipa_data *data)
 
 	/* Max outstanding read accesses for QSB masters */
 	val = u32_encode_bits(data0->max_reads, GEN_QMB_0_MAX_READS_FMASK);
-	/* GEN_QMB_0_MAX_READS_BEATS is 0 (IPA v4.0 and above) */
-	if (data->qsb_count > 1)
+	if (ipa->version >= IPA_VERSION_4_0)
+		val |= u32_encode_bits(data0->max_reads_beats,
+				       GEN_QMB_0_MAX_READS_BEATS_FMASK);
+	if (data->qsb_count > 1) {
 		val |= u32_encode_bits(data1->max_reads,
 				       GEN_QMB_1_MAX_READS_FMASK);
+		if (ipa->version >= IPA_VERSION_4_0)
+			val |= u32_encode_bits(data1->max_reads_beats,
+					       GEN_QMB_1_MAX_READS_BEATS_FMASK);
+	}
 	iowrite32(val, ipa->reg_virt + IPA_REG_QSB_MAX_READS_OFFSET);
 }