Date:   Tue, 8 May 2018 11:36:51 +0200
From:   Andrea Greco <andrea.greco.gapmilano@...il.com>
To:     "Tobin C. Harding" <tobin@...orbit.com>
Cc:     m.grzeschik@...gutronix.de, Andrea Greco <a.greco@...gma.it>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/3] arcnet: com20020: Add memory map of com20020

On 05/07/2018 04:55 AM, Tobin C. Harding wrote:
> On Sat, May 05, 2018 at 11:34:45PM +0200, Andrea Greco wrote:
>> From: Andrea Greco <a.greco@...gma.it>
> 
> Hi Andrea,
> 
> Here are some (mostly stylistic) suggestions to help you get your driver merged.
> 
>> Add support for com20022I/com20020, memory mapped chip version.
>> Support bus: Intel 80xx and Motorola 68xx.
>> Bus size: Only 8 bit bus size is supported.
>> Added related device tree bindings
>>
>> Signed-off-by: Andrea Greco <a.greco@...gma.it>
>> ---
>>   .../devicetree/bindings/net/smsc-com20020.txt      |  23 +++
>>   drivers/net/arcnet/Kconfig                         |  12 +-
>>   drivers/net/arcnet/Makefile                        |   1 +
>>   drivers/net/arcnet/arcdevice.h                     |  27 ++-
>>   drivers/net/arcnet/com20020-membus.c               | 191 +++++++++++++++++++++
>>   drivers/net/arcnet/com20020.c                      |   9 +-
>>   6 files changed, 253 insertions(+), 10 deletions(-)
>>   create mode 100644 Documentation/devicetree/bindings/net/smsc-com20020.txt
>>   create mode 100644 drivers/net/arcnet/com20020-membus.c
>>
>> diff --git a/Documentation/devicetree/bindings/net/smsc-com20020.txt b/Documentation/devicetree/bindings/net/smsc-com20020.txt
>> new file mode 100644
>> index 000000000000..39c5b19c55af
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/net/smsc-com20020.txt
>> @@ -0,0 +1,23 @@
>> +SMSC com20020, com20022I
>> +
>> +timeout: Arcnet timeout, checkout datashet
>> +clockp: Clock Prescaler, checkout datashet
>> +clockm: Clock multiplier, checkout datasheet
>> +
>> +phy-reset-gpios: Chip reset ppin
>> +phy-irq-gpios: Chip irq pin

ppin Corrected by my-self.

>> +
>> +com20020_A@0 {
>> +    compatible = "smsc,com20020";
>> +
>> +	timeout	= <0x3>;
>> +	backplane = <0x0>;
>> +
>> +	clockp = <0x0>;
>> +	clockm = <0x3>;
>> +
>> +	phy-reset-gpios = <&gpio3 21 GPIO_ACTIVE_LOW>;
>> +	phy-irq-gpios = <&gpio2 10 GPIO_ACTIVE_LOW>;
>> +
>> +	status = "okay";
>> +};
>> diff --git a/drivers/net/arcnet/Kconfig b/drivers/net/arcnet/Kconfig
>> index 39bd16f3f86d..d39faf45be1e 100644
>> --- a/drivers/net/arcnet/Kconfig
>> +++ b/drivers/net/arcnet/Kconfig
>> @@ -3,7 +3,7 @@
>>   #
>>   
>>   menuconfig ARCNET
>> -	depends on NETDEVICES && (ISA || PCI || PCMCIA)
>> +	depends on NETDEVICES
>>   	tristate "ARCnet support"
>>   	---help---
>>   	  If you have a network card of this type, say Y and check out the
>> @@ -129,5 +129,15 @@ config ARCNET_COM20020_CS
>>   
>>   	  To compile this driver as a module, choose M here: the module will be
>>   	  called com20020_cs.  If unsure, say N.
>> +config ARCNET_COM20020_MEMORY_BUS
>> +	bool "Support for COM20020 on external memory"
>> +	depends on ARCNET_COM20020 && !(ARCNET_COM20020_PCI || ARCNET_COM20020_ISA || ARCNET_COM20020_CS)
>> +	help
>> +	  Say Y here if on your custom board mount com20020 or friends.
>> +
>> +	  Com20022I support arcnet bus 10Mbitps.
>> +	  This driver support only 8bit
> 
> This driver only supports 8bit bus size.
> 
>>          	    	 	       , and DMA is not supported is attached on your board at external interface bus.
> 
> This bit does not make sense, sorry.
Removed description,

Proposal for v2:
Say Y here if your custom board mount com20020 chipset or friends.
Supported Chipset: com20020, com20022, com20022I-3v3.
If unsure, say N.

>> +	  Supported bus Intel80xx / Motorola 68xx.
>> +	  This driver not work with other com20020 module: PCI or PCMCIA compiled as [M].
> 
> I'm not sure exactly what you want to say here, perhaps:
> 
>    	  This driver does not work with other com20020 modules compiled
> 	  as PCI or PCMCIA [M].

About this, all removed from kconfig
For PCI, PCMCIA, checkout downside

>>   
>>   endif # ARCNET
>> diff --git a/drivers/net/arcnet/Makefile b/drivers/net/arcnet/Makefile
>> index 53525e8ea130..19425c1e06f4 100644
>> --- a/drivers/net/arcnet/Makefile
>> +++ b/drivers/net/arcnet/Makefile
>> @@ -14,3 +14,4 @@ obj-$(CONFIG_ARCNET_COM20020) += com20020.o
>>   obj-$(CONFIG_ARCNET_COM20020_ISA) += com20020-isa.o
>>   obj-$(CONFIG_ARCNET_COM20020_PCI) += com20020-pci.o
>>   obj-$(CONFIG_ARCNET_COM20020_CS) += com20020_cs.o
>> +obj-$(CONFIG_ARCNET_COM20020_MEMORY_BUS) += com20020-membus.o
>> diff --git a/drivers/net/arcnet/arcdevice.h b/drivers/net/arcnet/arcdevice.h
>> index d09b2b46ab63..16c608269cca 100644
>> --- a/drivers/net/arcnet/arcdevice.h
>> +++ b/drivers/net/arcnet/arcdevice.h
>> @@ -201,7 +201,7 @@ struct ArcProto {
>>   	void (*rx)(struct net_device *dev, int bufnum,
>>   		   struct archdr *pkthdr, int length);
>>   	int (*build_header)(struct sk_buff *skb, struct net_device *dev,
>> -			    unsigned short ethproto, uint8_t daddr);
>> +				unsigned short ethproto, uint8_t daddr);
> 
>    +			    unsigned short ethproto, uint8_t daddr);
> 
> Please use Linux coding style style, parameters continuing on separate
> line are aligned with opening parenthesis.
> 
>>   	/* these functions return '1' if the skb can now be freed */
>>   	int (*prepare_tx)(struct net_device *dev, struct archdr *pkt,
>> @@ -326,9 +326,9 @@ struct arcnet_local {
>>   		void (*recontrigger) (struct net_device * dev, int enable);
>>   
>>   		void (*copy_to_card)(struct net_device *dev, int bufnum,
>> -				     int offset, void *buf, int count);
>> +					 int offset, void *buf, int count);
>>   		void (*copy_from_card)(struct net_device *dev, int bufnum,
>> -				       int offset, void *buf, int count);
>> +					   int offset, void *buf, int count);
>>   	} hw;
>>   
>>   	void __iomem *mem_start;	/* pointer to ioremap'ed MMIO */
>> @@ -360,7 +360,7 @@ struct net_device *alloc_arcdev(const char *name);
>>   int arcnet_open(struct net_device *dev);
>>   int arcnet_close(struct net_device *dev);
>>   netdev_tx_t arcnet_send_packet(struct sk_buff *skb,
>> -			       struct net_device *dev);
>> +				   struct net_device *dev);
>>   void arcnet_timeout(struct net_device *dev);

Not required modification then all removed.

>>   
>>   /* I/O equivalents */
>> @@ -371,7 +371,23 @@ void arcnet_timeout(struct net_device *dev);
>>   #define BUS_ALIGN  1
>>   #endif
>>   
>> -/* addr and offset allow register like names to define the actual IO  address.
>> +#ifdef CONFIG_ARCNET_COM20020_MEMORY_BUS
>> +#define arcnet_inb(addr, offset)					\
>> +	ioread8((void __iomem *)(addr) + BUS_ALIGN * (offset))
>> +
>> +#define arcnet_outb(value, addr, offset)				\
>> +	iowrite8(value, (void __iomem *)(addr) + BUS_ALIGN * (offset))
>> +
>> +#define arcnet_insb(addr, offset, buffer, count)			\
>> +	ioread8_rep((void __iomem *)					\
>> +	(addr) + BUS_ALIGN * (offset), buffer, count)
>> +
>> +#define arcnet_outsb(addr, offset, buffer, count)			\
>> +	iowrite8_rep((void __iomem *)					\
>> +	(addr) + BUS_ALIGN * (offset), buffer, count)
>> +#else
>> +/**
>> + * addr and offset allow register like names to define the actual IO  address.
>>    * A configuration option multiplies the offset for alignment.
>>    */
>>   #define arcnet_inb(addr, offset)					\
>> @@ -388,6 +404,7 @@ void arcnet_timeout(struct net_device *dev);
>>   	readb((addr) + (offset))
>>   #define arcnet_writeb(value, addr, offset)				\
>>   	writeb(value, (addr) + (offset))
>> +#endif
>>   
>>   #endif				/* __KERNEL__ */
>>   #endif				/* _LINUX_ARCDEVICE_H */


This is most important part where a suggestion will be very appreciated.
This part define how arcnet drivers read and write over physical.
The old driver can always use readb/writeb and friends, this driver rise 
big kernel panic.

This driver make a ioreamp with: devm_ioremap.
Then, for r/w operation i use ioread8/iowrite8 and friends.

My quickly solution was make a ugly #ifdef.

With #ifndef all other driver implementation could not be used together
this driver, because break, how driver write over physical.
A proposal could be add a read/write callback to arcdevice.h struct hw.

PROS:
Every driver fill this callback, this is a solution.

CONS:
This solution require a small change for all com20020 driver
implementations. I don't dispose of all hardware for make a accurate
test. I could only test memory bus version.

Any other ideas, will be very appreciated.

>> diff --git a/drivers/net/arcnet/com20020-membus.c b/drivers/net/arcnet/com20020-membus.c
>> new file mode 100644
>> index 000000000000..6e4a2f3a84f7
>> --- /dev/null
>> +++ b/drivers/net/arcnet/com20020-membus.c
>> @@ -0,0 +1,191 @@
>> +// SPDX-License-Identifier: (GPL-2.0 OR MIT)
>> +/* Linux ARCnet driver for com 20020.
>> + *
>> + * This datasheet:
>> + * http://ww1.microchip.com/downloads/en/DeviceDoc/200223vrevc.pdf
>> + * http://ww1.microchip.com/downloads/en/DeviceDoc/20020.pdf
>> + *
>> + * This driver support:
> 
>      * This driver supports:
> 
>> + * - com20020,
>> + * - com20022
>> + * - com20022I-3v3
>> + *
>> + * This driver support only, 8bit read and write.
> 
>      * This driver supports only 8bit read and write.
> 
>> + * DMA is not supported by this driver.
>> + */
>> +#include <linux/module.h>
>> +#include <linux/types.h>
>> +#include <linux/device.h>
>> +#include <linux/kernel.h>
>> +#include <linux/errno.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/netdevice.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_gpio.h>
>> +#include <linux/sizes.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/ioport.h>
>> +#include <linux/random.h>
>> +
>> +#include <linux/delay.h>
>> +#include "arcdevice.h"
>> +#include "com20020.h"
> 
> White space line is not needed here, you might have meant to have it one
> line down?
>
Removed

>> +
>> +#define VERSION "arcnet: COM20020 MEMORY BUS support loaded.\n"
>> +
>> +static int com20020_probe(struct platform_device *pdev)
>> +{
>> +	struct device_node *np;
>> +	struct net_device *dev;
>> +	struct arcnet_local *lp;
>> +	struct resource res, *iores;
>> +	int ret, phy_reset, err;
>> +	u32 timeout, backplane, clockp, clockm;
>> +	void __iomem *ioaddr;
>> +
>> +	np = pdev->dev.of_node;
>> +
>> +	iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +
>> +	if (of_address_to_resource(np, 0, &res))
>> +		return -EINVAL;
>> +
>> +	ret = of_property_read_u32(np, "timeout", &timeout);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "timeout is required param");
>> +		return ret;
>> +	}
>> +
>> +	ret = of_property_read_u32(np, "backplane", &backplane);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "backplane is required param");
>> +		return ret;
>> +	}
>> +
>> +	ret = of_property_read_u32(np, "clockp", &clockp);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "clockp is required param");
>> +		return ret;
>> +	}
>> +
>> +	ret = of_property_read_u32(np, "clockm", &clockm);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "clockm is required param");
>> +		return ret;
>> +	}
>> +
>> +	phy_reset = of_get_named_gpio(np, "phy-reset-gpios", 0);
>> +	if (phy_reset == -EPROBE_DEFER) {
>> +		return phy_reset;
>> +	} else if (!gpio_is_valid(phy_reset)) {
>> +		dev_err(&pdev->dev, "phy-reset-gpios not valid !");
>> +		return 0;
>> +	}
>> +
>> +	err = devm_gpio_request_one(&pdev->dev, phy_reset, GPIOF_OUT_INIT_LOW,
>> +				    "arcnet-phy-reset");
>> +	if (err) {
>> +		dev_err(&pdev->dev, "failed to get phy-reset-gpios: %d\n", err);
>> +		return err;
>> +	}
>> +
>> +	dev = alloc_arcdev(NULL);// Let autoassign name arc%d
> 
> /* C89 style comments please */

All comment bring to C89

> 
>> +	dev->netdev_ops = &com20020_netdev_ops;
>> +	lp = netdev_priv(dev);
>> +
>> +	lp->card_flags = ARC_CAN_10MBIT;/* pretend all of them can 10Mbit */
>> +
>> +	// Force address to 0
> 
Removed
> Unnecessary, we can see this in the code :)  Please don't comment 'what'
> the code does (unless it is obfuscated or difficult to read).  You may
> still like to comment 'why' the code does what it does though.
> 
>> +	// Will be set by user with `ip set dev arc0 address YOUR_NODE_ID`
>> +	dev->dev_addr[0] = 0;
>> +

All this become
/* Will be set by userspace during if setup */

>> +	// request to system this memory region
> 
> Same as above
> 
Removed

>> +	if (!devm_request_mem_region(&pdev->dev, res.start, resource_size(&res),
>> +				     lp->card_name))
>> +		return -EBUSY;
>> +
>> +	ioaddr = devm_ioremap(&pdev->dev, iores->start, resource_size(iores));
>> +	if (!ioaddr) {
>> +		dev_err(&pdev->dev, "ioremap fallied\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	// Reset time is 5 * xTalFreq, minimal xtal is 10Mhz
>> +	// (5 * 1000) / 10Mhz = 500ns
> 
> perhaps a macro definition
> #define MAX_XTAL_RESET_TIME ??

Macro made, on head of file.
Rereading Datasheet maby that last delay could be removed.
Then become
	gpio_set_value_cansleep(phy_reset, 0);
	ndelay(RESET_DELAY);
	gpio_set_value_cansleep(phy_reset, 1);
>> +
>> +	gpio_set_value_cansleep(phy_reset, 0);
>> +	ndelay(500);
>> +	gpio_set_value_cansleep(phy_reset, 1);
>> +	ndelay(500);
>> +
>> +	/* Dummy access after Reset
>> +	 * ARCNET controller needs
>> +	 * this access to detect bustype
>> +	 */
> 
> nit: Upto 72 characters wide is fine for comments
> 
> 	/* Dummy access after Reset ARCNET controller needs
> 	 * this access to detect bustype
> 	 */
> 
>> +	arcnet_outb(0x00, ioaddr, COM20020_REG_W_COMMAND);
>> +	arcnet_inb(ioaddr, COM20020_REG_R_DIAGSTAT);
>> +

Changed in:
	/* ARCNET controller needs this access to detect bustype */
	arcnet_outb(0x00, ioaddr, COM20020_REG_W_COMMAND);
	arcnet_inb(ioaddr, COM20020_REG_R_DIAGSTAT);

>> +	dev->base_addr = (unsigned long)ioaddr;
>> +	get_random_bytes(dev->dev_addr, sizeof(u8));
>> +
>> +	dev->irq = of_get_named_gpio(np, "phy-irq-gpios", 0);
>> +	if (dev->irq == -EPROBE_DEFER) {
>> +		return dev->irq;
>> +	} else if (!gpio_is_valid(dev->irq)) {
>> +		dev_err(&pdev->dev, "phy-irq-gpios not valid !");
>> +		return 0;
>> +	}
>> +	dev->irq = gpio_to_irq(dev->irq);
>> +
>> +	lp->backplane = backplane;
>> +	lp->clockp = clockp & 7;
>> +	lp->clockm = clockm & 3;
>> +	lp->timeout = timeout;
>> +	lp->hw.owner = THIS_MODULE;
>> +
>> +	if (arcnet_inb(ioaddr, COM20020_REG_R_STATUS) == 0xFF) {
>> +		ret = -EIO;
>> +		goto err_release_mem;
>> +	}
>> +
>> +	if (com20020_check(dev)) {
>> +		ret = -EIO;
>> +		goto err_release_mem;
>> +	}
>> +
>> +	ret = com20020_found(dev, IRQF_TRIGGER_FALLING);
>> +	if (ret)
>> +		goto err_release_mem;
>> +
>> +	dev_dbg(&pdev->dev, "probe Done\n");
>> +	return 0;
>> +
>> +err_release_mem:
>> +	devm_iounmap(&pdev->dev, (void __iomem *)ioaddr);
>> +	devm_release_mem_region(&pdev->dev, res.start, resource_size(&res));
>> +	dev_err(&pdev->dev, "probe failed!\n");
>> +	return ret;
>> +}
>> +
>> +static const struct of_device_id of_com20020_match[] = {
>> +	{ .compatible = "smsc,com20020",	},
>> +	{ },
>> +};
>> +
>> +MODULE_DEVICE_TABLE(of, of_com20020_match);
>> +
>> +static struct platform_driver of_com20020_driver = {
>> +	.driver			= {
>> +		.name		= "com20020-memory-bus",
>> +		.of_match_table = of_com20020_match,
>> +	},
>> +	.probe			= com20020_probe,
>> +};
>> +
>> +static int com20020_init(void)
>> +{
>> +	return platform_driver_register(&of_com20020_driver);
>> +}
>> +late_initcall(com20020_init);
>> +
>> +MODULE_LICENSE("GPL");
>> diff --git a/drivers/net/arcnet/com20020.c b/drivers/net/arcnet/com20020.c
>> index 78043a9c5981..f09ea77dd6a8 100644
>> --- a/drivers/net/arcnet/com20020.c
>> +++ b/drivers/net/arcnet/com20020.c
>> @@ -43,7 +43,7 @@
>>   #include "com20020.h"
>>   
>>   static const char * const clockrates[] = {
>> -	"XXXXXXX", "XXXXXXXX", "XXXXXX", "2.5 Mb/s",
>> +	"10 Mb/s", "XXXXXXXX", "XXXXXX", "2.5 Mb/s",
>>   	"1.25Mb/s", "625 Kb/s", "312.5 Kb/s", "156.25 Kb/s",
>>   	"Reserved", "Reserved", "Reserved"
>>   };
>> @@ -391,9 +391,10 @@ static void com20020_set_mc_list(struct net_device *dev)
>>   	}
>>   }
>>   
>> -#if defined(CONFIG_ARCNET_COM20020_PCI_MODULE) || \
>> -    defined(CONFIG_ARCNET_COM20020_ISA_MODULE) || \
>> -    defined(CONFIG_ARCNET_COM20020_CS_MODULE)
>> +#if	defined(CONFIG_ARCNET_COM20020_PCI_MODULE) || \
>> +	defined(CONFIG_ARCNET_COM20020_ISA_MODULE) || \
>> +	defined(CONFIG_ARCNET_COM20020_CS_MODULE)  || \
>> +	defined(CONFIG_ARCNET_COM20020_MEMORY_BUS)
> 
> Why the whitespace change?

      defined(CONFIG_ARCNET_COM20020_ISA_MODULE) || \
-    defined(CONFIG_ARCNET_COM20020_CS_MODULE)
+    defined(CONFIG_ARCNET_COM20020_CS_MODULE)  || \
+    defined(CONFIG_ARCNET_COM20020_MEMORY_BUS)

Removed useless withespace

> 
> Hope this helps,
> Tobin.
> 

Thank you for help,
Andrea

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