HID: intel-ish-hid: ishtp: Add dma_no_cache_snooping() callback

Different platforms have different DMA capability, on most of
platforms, DMA support cache snooping. But few platforms,
such as ElkhartLake (EHL), don't support cache snooping
which requires cache flush from driver.

So add a hardware level callback to let ishtp driver know if cache
flush is needed.

As most of platform support cache snooping, so driver will not
do cache flush by default, until platform implements this callback
and return true explicitly.
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/ishtp/client.c

@@ -10,6 +10,7 @@
 #include <linux/wait.h>
 #include <linux/delay.h>
 #include <linux/dma-mapping.h>
+#include <asm/cacheflush.h>
 #include "hbm.h"
 #include "client.h"
 
@@ -772,6 +773,14 @@ static void ishtp_cl_send_msg_dma(struct ishtp_device *dev,
 	/* write msg to dma buf */
 	memcpy(msg_addr, cl_msg->send_buf.data, cl_msg->send_buf.size);
 
+	/*
+	 * if current fw don't support cache snooping, driver have to
+	 * flush the cache manually.
+	 */
+	if (dev->ops->dma_no_cache_snooping &&
+		dev->ops->dma_no_cache_snooping(dev))
+		clflush_cache_range(msg_addr, cl_msg->send_buf.size);
+
 	/* send dma_xfer hbm msg */
 	off = msg_addr - (unsigned char *)dev->ishtp_host_dma_tx_buf;
 	ishtp_hbm_hdr(&hdr, sizeof(struct dma_xfer_hbm));
@@ -996,6 +1005,15 @@ void recv_ishtp_cl_msg_dma(struct ishtp_device *dev, void *msg,
 		}
 
 		buffer = rb->buffer.data;
+
+		/*
+		 * if current fw don't support cache snooping, driver have to
+		 * flush the cache manually.
+		 */
+		if (dev->ops->dma_no_cache_snooping &&
+			dev->ops->dma_no_cache_snooping(dev))
+			clflush_cache_range(msg, hbm->msg_length);
+
 		memcpy(buffer, msg, hbm->msg_length);
 		rb->buf_idx = hbm->msg_length;
 

drivers/hid/intel-ish-hid/ishtp/ishtp-dev.h

@@ -119,6 +119,7 @@ struct ishtp_hw_ops {
 			unsigned long buffer_length);
 	uint32_t	(*get_fw_status)(struct ishtp_device *dev);
 	void	(*sync_fw_clock)(struct ishtp_device *dev);
+	bool	(*dma_no_cache_snooping)(struct ishtp_device *dev);
 };
 
 /**