HID: intel-ish-hid: ipc: Specify that EHL no cache snooping

Specify that EHL doesn't support DMA cache snooping.
Acked-by: Pandruvada, Srinivas <srinivas.pandruvada@intel.com>
Signed-off-by: Even Xu <even.xu@intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/intel-ish-hid/ipc/ipc.c

@@ -889,6 +889,29 @@ static uint32_t ish_ipc_get_header(struct ishtp_device *dev, int length,
 	return drbl_val;
 }
 
+/**
+ * _dma_no_cache_snooping()
+ *
+ * Check on current platform, DMA supports cache snooping or not.
+ * This callback is used to notify uplayer driver if manully cache
+ * flush is needed when do DMA operation.
+ *
+ * Please pay attention to this callback implementation, if declare
+ * having cache snooping on a cache snooping not supported platform
+ * will cause uplayer driver receiving mismatched data; and if
+ * declare no cache snooping on a cache snooping supported platform
+ * will cause cache be flushed twice and performance hit.
+ *
+ * @dev: ishtp device pointer
+ *
+ * Return: false - has cache snooping capability
+ *         true - no cache snooping, need manually cache flush
+ */
+static bool _dma_no_cache_snooping(struct ishtp_device *dev)
+{
+	return dev->pdev->device == EHL_Ax_DEVICE_ID;
+}
+
 static const struct ishtp_hw_ops ish_hw_ops = {
 	.hw_reset = _ish_hw_reset,
 	.ipc_reset = _ish_ipc_reset,
@@ -897,7 +920,8 @@ static const struct ishtp_hw_ops ish_hw_ops = {
 	.write = write_ipc_to_queue,
 	.get_fw_status = _ish_read_fw_sts_reg,
 	.sync_fw_clock = _ish_sync_fw_clock,
-	.ishtp_read_hdr = _ishtp_read_hdr
+	.ishtp_read_hdr = _ishtp_read_hdr,
+	.dma_no_cache_snooping = _dma_no_cache_snooping
 };
 
 /**