net: aquantia: fix potential IOMMU fault after driver unbind

IOMMU fault may occurr on unbind/bind or if_down/if_up sequence.

Although driver disables the rings on down, this is not enough.
Due to internal HW design, during subsequent initialization
NIC sometimes may reuse RX descriptors cache and write to the
host memory from the descriptor cache.
That's get catched by IOMMU on host.

This patch invalidates the descriptor cache in NIC on interface down
to prevent writing to the cached descriptors and to the memory pointed
in those descriptors.

Signed-off-by: Dmitry Bogdanov <dmitry.bogdanov@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c

@@ -920,6 +920,12 @@ static int hw_atl_b0_hw_interrupt_moderation_set(struct aq_hw_s *self)
 static int hw_atl_b0_hw_stop(struct aq_hw_s *self)
 {
 	hw_atl_b0_hw_irq_disable(self, HW_ATL_B0_INT_MASK);
+
+	/* Invalidate Descriptor Cache to prevent writing to the cached
+	 * descriptors and to the data pointer of those descriptors
+	 */
+	hw_atl_rdm_rx_dma_desc_cache_init_set(self, 1);
+
 	return aq_hw_err_from_flags(self);
 }
 

drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_llh.c

@@ -619,6 +619,14 @@ void hw_atl_rpb_rx_flow_ctl_mode_set(struct aq_hw_s *aq_hw, u32 rx_flow_ctl_mode
 			    HW_ATL_RPB_RX_FC_MODE_SHIFT, rx_flow_ctl_mode);
 }
 
+void hw_atl_rdm_rx_dma_desc_cache_init_set(struct aq_hw_s *aq_hw, u32 init)
+{
+	aq_hw_write_reg_bit(aq_hw, HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_ADR,
+			    HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_MSK,
+			    HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_SHIFT,
+			    init);
+}
+
 void hw_atl_rpb_rx_pkt_buff_size_per_tc_set(struct aq_hw_s *aq_hw,
 					    u32 rx_pkt_buff_size_per_tc, u32 buffer)
 {

drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_llh.h

@@ -325,6 +325,9 @@ void hw_atl_rpb_rx_pkt_buff_size_per_tc_set(struct aq_hw_s *aq_hw,
 					    u32 rx_pkt_buff_size_per_tc,
 					    u32 buffer);
 
+/* set rdm rx dma descriptor cache init */
+void hw_atl_rdm_rx_dma_desc_cache_init_set(struct aq_hw_s *aq_hw, u32 init);
+
 /* set rx xoff enable (per tc) */
 void hw_atl_rpb_rx_xoff_en_per_tc_set(struct aq_hw_s *aq_hw, u32 rx_xoff_en_per_tc,
 				      u32 buffer);

drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_llh_internal.h

@@ -293,6 +293,24 @@
 /* default value of bitfield desc{d}_reset */
 #define HW_ATL_RDM_DESCDRESET_DEFAULT 0x0
 
+/* rdm_desc_init_i bitfield definitions
+ * preprocessor definitions for the bitfield rdm_desc_init_i.
+ * port="pif_rdm_desc_init_i"
+ */
+
+/* register address for bitfield rdm_desc_init_i */
+#define HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_ADR 0x00005a00
+/* bitmask for bitfield rdm_desc_init_i */
+#define HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_MSK 0xffffffff
+/* inverted bitmask for bitfield rdm_desc_init_i */
+#define HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_MSKN 0x00000000
+/* lower bit position of bitfield  rdm_desc_init_i */
+#define HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_SHIFT 0
+/* width of bitfield rdm_desc_init_i */
+#define HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_WIDTH 32
+/* default value of bitfield rdm_desc_init_i */
+#define HW_ATL_RDM_RX_DMA_DESC_CACHE_INIT_DEFAULT 0x0
+
 /* rx int_desc_wrb_en bitfield definitions
  * preprocessor definitions for the bitfield "int_desc_wrb_en".
  * port="pif_rdm_int_desc_wrb_en_i"