net: aquantia: Fix hardware DMA stream overload on large MRRS

Systems with large MRRS on device (2K, 4K) with high data rates and/or
large MTU, atlantic observes DMA packet buffer overflow. On some systems
that causes PCIe transaction errors, hardware NMIs or datapath freeze.
This patch
1) Limits MRRS from device side to 2K (thats maximum our hardware supports)
2) Limit maximum size of outstanding TX DMA data read requests. This makes
hardware buffers running fine.

Signed-off-by: Pavel Belous <pavel.belous@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

@@ -16,6 +16,7 @@
 #include "hw_atl_utils.h"
 #include "hw_atl_llh.h"
 #include "hw_atl_b0_internal.h"
+#include "hw_atl_llh_internal.h"
 
 static int hw_atl_b0_get_hw_caps(struct aq_hw_s *self,
 				 struct aq_hw_caps_s *aq_hw_caps,
@@ -368,6 +369,7 @@ static int hw_atl_b0_hw_init(struct aq_hw_s *self,
 	};
 
 	int err = 0;
+	u32 val;
 
 	self->aq_nic_cfg = aq_nic_cfg;
 
@@ -385,6 +387,16 @@ static int hw_atl_b0_hw_init(struct aq_hw_s *self,
 	hw_atl_b0_hw_rss_set(self, &aq_nic_cfg->aq_rss);
 	hw_atl_b0_hw_rss_hash_set(self, &aq_nic_cfg->aq_rss);
 
+	/* Force limit MRRS on RDM/TDM to 2K */
+	val = aq_hw_read_reg(self, pci_reg_control6_adr);
+	aq_hw_write_reg(self, pci_reg_control6_adr, (val & ~0x707) | 0x404);
+
+	/* TX DMA total request limit. B0 hardware is not capable to
+	 * handle more than (8K-MRRS) incoming DMA data.
+	 * Value 24 in 256byte units
+	 */
+	aq_hw_write_reg(self, tx_dma_total_req_limit_adr, 24);
+
 	err = aq_hw_err_from_flags(self);
 	if (err < 0)
 		goto err_exit;

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

@@ -2343,6 +2343,9 @@
 #define tx_dma_desc_base_addrmsw_adr(descriptor) \
 			(0x00007c04u + (descriptor) * 0x40)
 
+/* tx dma total request limit */
+#define tx_dma_total_req_limit_adr 0x00007b20u
+
 /* tx interrupt moderation control register definitions
  * Preprocessor definitions for TX Interrupt Moderation Control Register
  * Base Address: 0x00008980
@@ -2369,6 +2372,9 @@
 /* default value of bitfield reg_res_dsbl */
 #define pci_reg_res_dsbl_default 0x1
 
+/* PCI core control register */
+#define pci_reg_control6_adr 0x1014u
+
 /* global microprocessor scratch pad definitions */
 #define glb_cpu_scratch_scp_adr(scratch_scp) (0x00000300u + (scratch_scp) * 0x4)