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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:47 EST.

1	       STMicroelectronics 10/100/1000 Synopsys Ethernet driver
2	
3	Copyright (C) 2007-2015  STMicroelectronics Ltd
4	Author: Giuseppe Cavallaro <peppe.cavallaro@st.com>
5	
6	This is the driver for the MAC 10/100/1000 on-chip Ethernet controllers
7	(Synopsys IP blocks).
8	
9	Currently this network device driver is for all STi embedded MAC/GMAC
10	(i.e. 7xxx/5xxx SoCs), SPEAr (arm), Loongson1B (mips) and XLINX XC2V3000
11	FF1152AMT0221 D1215994A VIRTEX FPGA board.
12	
13	DWC Ether MAC 10/100/1000 Universal version 3.70a (and older) and DWC Ether
14	MAC 10/100 Universal version 4.0 have been used for developing this driver.
15	
16	This driver supports both the platform bus and PCI.
17	
18	Please, for more information also visit: www.stlinux.com
19	
20	1) Kernel Configuration
21	The kernel configuration option is STMMAC_ETH:
22	 Device Drivers ---> Network device support ---> Ethernet (1000 Mbit) --->
23	 STMicroelectronics 10/100/1000 Ethernet driver (STMMAC_ETH)
24	
25	CONFIG_STMMAC_PLATFORM: is to enable the platform driver.
26	CONFIG_STMMAC_PCI: is to enable the pci driver.
27	
28	2) Driver parameters list:
29		debug: message level (0: no output, 16: all);
30		phyaddr: to manually provide the physical address to the PHY device;
31		dma_rxsize: DMA rx ring size;
32		dma_txsize: DMA tx ring size;
33		buf_sz: DMA buffer size;
34		tc: control the HW FIFO threshold;
35		watchdog: transmit timeout (in milliseconds);
36		flow_ctrl: Flow control ability [on/off];
37		pause: Flow Control Pause Time;
38		eee_timer: tx EEE timer;
39		chain_mode: select chain mode instead of ring.
40	
41	3) Command line options
42	Driver parameters can be also passed in command line by using:
43		stmmaceth=dma_rxsize:128,dma_txsize:512
44	
45	4) Driver information and notes
46	
47	4.1) Transmit process
48	The xmit method is invoked when the kernel needs to transmit a packet; it sets
49	the descriptors in the ring and informs the DMA engine that there is a packet
50	ready to be transmitted.
51	By default, the driver sets the NETIF_F_SG bit in the features field of the
52	net_device structure enabling the scatter-gather feature. This is true on
53	chips and configurations where the checksum can be done in hardware.
54	Once the controller has finished transmitting the packet, napi will be
55	scheduled to release the transmit resources.
56	
57	4.2) Receive process
58	When one or more packets are received, an interrupt happens. The interrupts
59	are not queued so the driver has to scan all the descriptors in the ring during
60	the receive process.
61	This is based on NAPI so the interrupt handler signals only if there is work
62	to be done, and it exits.
63	Then the poll method will be scheduled at some future point.
64	The incoming packets are stored, by the DMA, in a list of pre-allocated socket
65	buffers in order to avoid the memcpy (zero-copy).
66	
67	4.3) Interrupt Mitigation
68	The driver is able to mitigate the number of its DMA interrupts
69	using NAPI for the reception on chips older than the 3.50.
70	New chips have an HW RX-Watchdog used for this mitigation.
71	Mitigation parameters can be tuned by ethtool.
72	
73	4.4) WOL
74	Wake up on Lan feature through Magic and Unicast frames are supported for the
75	GMAC core.
76	
77	4.5) DMA descriptors
78	Driver handles both normal and alternate descriptors. The latter has been only
79	tested on DWC Ether MAC 10/100/1000 Universal version 3.41a and later.
80	
81	STMMAC supports DMA descriptor to operate both in dual buffer (RING)
82	and linked-list(CHAINED) mode. In RING each descriptor points to two
83	data buffer pointers whereas in CHAINED mode they point to only one data
84	buffer pointer. RING mode is the default.
85	
86	In CHAINED mode each descriptor will have pointer to next descriptor in
87	the list, hence creating the explicit chaining in the descriptor itself,
88	whereas such explicit chaining is not possible in RING mode.
89	
90	4.5.1) Extended descriptors
91		The extended descriptors give us information about the Ethernet payload
92		when it is carrying PTP packets or TCP/UDP/ICMP over IP.
93		These are not available on GMAC Synopsys chips older than the 3.50.
94		At probe time the driver will decide if these can be actually used.
95		This support also is mandatory for PTPv2 because the extra descriptors
96		are used for saving the hardware timestamps and Extended Status.
97	
98	4.6) Ethtool support
99	Ethtool is supported.
100	
101	For example, driver statistics (including RMON), internal errors can be taken
102	using:
103	  # ethtool -S ethX command
104	
105	4.7) Jumbo and Segmentation Offloading
106	Jumbo frames are supported and tested for the GMAC.
107	The GSO has been also added but it's performed in software.
108	LRO is not supported.
109	
110	4.8) Physical
111	The driver is compatible with Physical Abstraction Layer to be connected with
112	PHY and GPHY devices.
113	
114	4.9) Platform information
115	Several information can be passed through the platform and device-tree.
116	
117	struct plat_stmmacenet_data {
118		char *phy_bus_name;
119		int bus_id;
120		int phy_addr;
121		int interface;
122		struct stmmac_mdio_bus_data *mdio_bus_data;
123		struct stmmac_dma_cfg *dma_cfg;
124		int clk_csr;
125		int has_gmac;
126		int enh_desc;
127		int tx_coe;
128		int rx_coe;
129		int bugged_jumbo;
130		int pmt;
131		int force_sf_dma_mode;
132		int force_thresh_dma_mode;
133		int riwt_off;
134		int max_speed;
135		int maxmtu;
136		void (*fix_mac_speed)(void *priv, unsigned int speed);
137		void (*bus_setup)(void __iomem *ioaddr);
138		int (*init)(struct platform_device *pdev, void *priv);
139		void (*exit)(struct platform_device *pdev, void *priv);
140		void *bsp_priv;
141		int has_gmac4;
142		bool tso_en;
143	};
144	
145	Where:
146	 o phy_bus_name: phy bus name to attach to the stmmac.
147	 o bus_id: bus identifier.
148	 o phy_addr: the physical address can be passed from the platform.
149		    If it is set to -1 the driver will automatically
150		    detect it at run-time by probing all the 32 addresses.
151	 o interface: PHY device's interface.
152	 o mdio_bus_data: specific platform fields for the MDIO bus.
153	 o dma_cfg: internal DMA parameters
154	   o pbl: the Programmable Burst Length is maximum number of beats to
155	       be transferred in one DMA transaction.
156	       GMAC also enables the 4xPBL by default.
157	   o fixed_burst/mixed_burst/burst_len
158	 o clk_csr: fixed CSR Clock range selection.
159	 o has_gmac: uses the GMAC core.
160	 o enh_desc: if sets the MAC will use the enhanced descriptor structure.
161	 o tx_coe: core is able to perform the tx csum in HW.
162	 o rx_coe: the supports three check sum offloading engine types:
163		   type_1, type_2 (full csum) and no RX coe.
164	 o bugged_jumbo: some HWs are not able to perform the csum in HW for
165			over-sized frames due to limited buffer sizes.
166			Setting this flag the csum will be done in SW on
167			JUMBO frames.
168	 o pmt: core has the embedded power module (optional).
169	 o force_sf_dma_mode: force DMA to use the Store and Forward mode
170			     instead of the Threshold.
171	 o force_thresh_dma_mode: force DMA to use the Threshold mode other than
172			     the Store and Forward mode.
173	 o riwt_off: force to disable the RX watchdog feature and switch to NAPI mode.
174	 o fix_mac_speed: this callback is used for modifying some syscfg registers
175			 (on ST SoCs) according to the link speed negotiated by the
176			 physical layer .
177	 o bus_setup: perform HW setup of the bus. For example, on some ST platforms
178		     this field is used to configure the AMBA  bridge to generate more
179		     efficient STBus traffic.
180	 o init/exit: callbacks used for calling a custom initialization;
181		     this is sometime necessary on some platforms (e.g. ST boxes)
182		     where the HW needs to have set some PIO lines or system cfg
183		     registers.  init/exit callbacks should not use or modify
184		     platform data.
185	 o bsp_priv: another private pointer.
186	 o has_gmac4: uses GMAC4 core.
187	 o tso_en: Enables TSO (TCP Segmentation Offload) feature.
188	
189	For MDIO bus The we have:
190	
191	 struct stmmac_mdio_bus_data {
192		int (*phy_reset)(void *priv);
193		unsigned int phy_mask;
194		int *irqs;
195		int probed_phy_irq;
196	 };
197	
198	Where:
199	 o phy_reset: hook to reset the phy device attached to the bus.
200	 o phy_mask: phy mask passed when register the MDIO bus within the driver.
201	 o irqs: list of IRQs, one per PHY.
202	 o probed_phy_irq: if irqs is NULL, use this for probed PHY.
203	
204	For DMA engine we have the following internal fields that should be
205	tuned according to the HW capabilities.
206	
207	struct stmmac_dma_cfg {
208		int pbl;
209		int fixed_burst;
210		int burst_len_supported;
211	};
212	
213	Where:
214	 o pbl: Programmable Burst Length
215	 o fixed_burst: program the DMA to use the fixed burst mode
216	 o burst_len: this is the value we put in the register
217		      supported values are provided as macros in
218		      linux/stmmac.h header file.
219	
220	---
221	
222	Below an example how the structures above are using on ST platforms.
223	
224	 static struct plat_stmmacenet_data stxYYY_ethernet_platform_data = {
225		.has_gmac = 0,
226		.enh_desc = 0,
227		.fix_mac_speed = stxYYY_ethernet_fix_mac_speed,
228					|
229					|-> to write an internal syscfg
230					|   on this platform when the
231					|   link speed changes from 10 to
232					|   100 and viceversa
233		.init = &stmmac_claim_resource,
234					|
235					|-> On ST SoC this calls own "PAD"
236					|   manager framework to claim
237					|   all the resources necessary
238					|   (GPIO ...). The .custom_cfg field
239					|   is used to pass a custom config.
240	};
241	
242	Below the usage of the stmmac_mdio_bus_data: on this SoC, in fact,
243	there are two MAC cores: one MAC is for MDIO Bus/PHY emulation
244	with fixed_link support.
245	
246	static struct stmmac_mdio_bus_data stmmac1_mdio_bus = {
247		.phy_reset = phy_reset;
248			|
249			|-> function to provide the phy_reset on this board
250		.phy_mask = 0,
251	};
252	
253	static struct fixed_phy_status stmmac0_fixed_phy_status = {
254		.link = 1,
255		.speed = 100,
256		.duplex = 1,
257	};
258	
259	During the board's device_init we can configure the first
260	MAC for fixed_link by calling:
261	  fixed_phy_add(PHY_POLL, 1, &stmmac0_fixed_phy_status, -1);
262	and the second one, with a real PHY device attached to the bus,
263	by using the stmmac_mdio_bus_data structure (to provide the id, the
264	reset procedure etc).
265	
266	Note that, starting from new chips, where it is available the HW capability
267	register, many configurations are discovered at run-time for example to
268	understand if EEE, HW csum, PTP, enhanced descriptor etc are actually
269	available. As strategy adopted in this driver, the information from the HW
270	capability register can replace what has been passed from the platform.
271	
272	4.10) Device-tree support.
273	
274	Please see the following document:
275		Documentation/devicetree/bindings/net/stmmac.txt
276	
277	4.11) This is a summary of the content of some relevant files:
278	 o stmmac_main.c: to implement the main network device driver;
279	 o stmmac_mdio.c: to provide mdio functions;
280	 o stmmac_pci: this the PCI driver;
281	 o stmmac_platform.c: this the platform driver (OF supported)
282	 o stmmac_ethtool.c: to implement the ethtool support;
283	 o stmmac.h: private driver structure;
284	 o common.h: common definitions and VFTs;
285	 o mmc_core.c/mmc.h: Management MAC Counters;
286	 o stmmac_hwtstamp.c: HW timestamp support for PTP;
287	 o stmmac_ptp.c: PTP 1588 clock;
288	 o dwmac-<XXX>.c: these are for the platform glue-logic file; e.g. dwmac-sti.c
289	   for STMicroelectronics SoCs.
290	
291	- GMAC 3.x
292	 o descs.h: descriptor structure definitions;
293	 o dwmac1000_core.c: dwmac GiGa core functions;
294	 o dwmac1000_dma.c: dma functions for the GMAC chip;
295	 o dwmac1000.h: specific header file for the dwmac GiGa;
296	 o dwmac100_core: dwmac 100 core code;
297	 o dwmac100_dma.c: dma functions for the dwmac 100 chip;
298	 o dwmac1000.h: specific header file for the MAC;
299	 o dwmac_lib.c: generic DMA functions;
300	 o enh_desc.c: functions for handling enhanced descriptors;
301	 o norm_desc.c: functions for handling normal descriptors;
302	 o chain_mode.c/ring_mode.c:: functions to manage RING/CHAINED modes;
303	
304	- GMAC4.x generation
305	 o dwmac4_core.c: dwmac GMAC4.x core functions;
306	 o dwmac4_desc.c: functions for handling GMAC4.x descriptors;
307	 o dwmac4_descs.h: descriptor definitions;
308	 o dwmac4_dma.c: dma functions for the GMAC4.x chip;
309	 o dwmac4_dma.h: dma definitions for the GMAC4.x chip;
310	 o dwmac4.h: core definitions for the GMAC4.x chip;
311	 o dwmac4_lib.c: generic GMAC4.x functions;
312	
313	4.12) TSO support (GMAC4.x)
314	
315	TSO (Tcp Segmentation Offload) feature is supported by GMAC 4.x chip family.
316	When a packet is sent through TCP protocol, the TCP stack ensures that
317	the SKB provided to the low level driver (stmmac in our case) matches with
318	the maximum frame len (IP header + TCP header + payload <= 1500 bytes (for
319	MTU set to 1500)). It means that if an application using TCP want to send a
320	packet which will have a length (after adding headers) > 1514 the packet
321	will be split in several TCP packets: The data payload is split and headers
322	(TCP/IP ..) are added. It is done by software.
323	
324	When TSO is enabled, the TCP stack doesn't care about the maximum frame
325	length and provide SKB packet to stmmac as it is. The GMAC IP will have to
326	perform the segmentation by it self to match with maximum frame length.
327	
328	This feature can be enabled in device tree through "snps,tso" entry.
329	
330	5) Debug Information
331	
332	The driver exports many information i.e. internal statistics,
333	debug information, MAC and DMA registers etc.
334	
335	These can be read in several ways depending on the
336	type of the information actually needed.
337	
338	For example a user can be use the ethtool support
339	to get statistics: e.g. using: ethtool -S ethX
340	(that shows the Management counters (MMC) if supported)
341	or sees the MAC/DMA registers: e.g. using: ethtool -d ethX
342	
343	Compiling the Kernel with CONFIG_DEBUG_FS the driver will export the following
344	debugfs entries:
345	
346	/sys/kernel/debug/stmmaceth/descriptors_status
347	  To show the DMA TX/RX descriptor rings
348	
349	Developer can also use the "debug" module parameter to get further debug
350	information (please see: NETIF Msg Level).
351	
352	6) Energy Efficient Ethernet
353	
354	Energy Efficient Ethernet(EEE) enables IEEE 802.3 MAC sublayer along
355	with a family of Physical layer to operate in the Low power Idle(LPI)
356	mode. The EEE mode supports the IEEE 802.3 MAC operation at 100Mbps,
357	1000Mbps & 10Gbps.
358	
359	The LPI mode allows power saving by switching off parts of the
360	communication device functionality when there is no data to be
361	transmitted & received. The system on both the side of the link can
362	disable some functionalities & save power during the period of low-link
363	utilization. The MAC controls whether the system should enter or exit
364	the LPI mode & communicate this to PHY.
365	
366	As soon as the interface is opened, the driver verifies if the EEE can
367	be supported. This is done by looking at both the DMA HW capability
368	register and the PHY devices MCD registers.
369	To enter in Tx LPI mode the driver needs to have a software timer
370	that enable and disable the LPI mode when there is nothing to be
371	transmitted.
372	
373	7) Precision Time Protocol (PTP)
374	The driver supports the IEEE 1588-2002, Precision Time Protocol (PTP),
375	which enables precise synchronization of clocks in measurement and
376	control systems implemented with technologies such as network
377	communication.
378	
379	In addition to the basic timestamp features mentioned in IEEE 1588-2002
380	Timestamps, new GMAC cores support the advanced timestamp features.
381	IEEE 1588-2008 that can be enabled when configure the Kernel.
382	
383	8) SGMII/RGMII supports
384	New GMAC devices provide own way to manage RGMII/SGMII.
385	This information is available at run-time by looking at the
386	HW capability register. This means that the stmmac can manage
387	auto-negotiation and link status w/o using the PHYLIB stuff
388	In fact, the HW provides a subset of extended registers to
389	restart the ANE, verify Full/Half duplex mode and Speed.
390	Also thanks to these registers it is possible to look at the
391	Auto-negotiated Link Parter Ability.
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