Message-ID: <9D35ABAF307441FFAE50B3EAA521C4E0@subhasishg>
Date:	Tue, 22 Mar 2011 13:00:57 +0530
From:	"Subhasish Ghosh" <subhasish@...tralsolutions.com>
To:	"Arnd Bergmann" <arnd@...db.de>,
	<linux-arm-kernel@...ts.infradead.org>
Cc:	<davinci-linux-open-source@...ux.davincidsp.com>,
	<sachi@...tralsolutions.com>, <nsekhar@...com>,
	"open list" <linux-kernel@...r.kernel.org>,
	"open list:CAN NETWORK DRIVERS" <socketcan-core@...ts.berlios.de>,
	"open list:CAN NETWORK DRIVERS" <netdev@...r.kernel.org>,
	<m-watkins@...com>, "Wolfgang Grandegger" <wg@...ndegger.com>
Subject: Re: [PATCH v2 09/13] can: pruss CAN driver.

Hello,

> This is a detailed walk through the can driver. The pruss_can.c
> file mostly looks good, there are very tiny changes that I'm
> suggesting to improve the code. I assume that you wrote that file.
>
> The pruss_can_api.c is a bit of a mess and looks like it was copied
> from some other code base and just barely changed to follow Linux
> coding style. I can tell from the main driver file that you can do
> better than that.
> My recommendation for that would be to throw it away and reimplement
> the few parts that you actually need, in proper coding style.
> You can also try to fix the file according to the comments I give
> you below, but I assume that would be signficantly more work.
>
> Moving everything into one file also makes things easier to read
> here and lets you identifer more quickly what is unused.

SG - I have almost re-implemented the API layer, will be merging with the 
driver file itself.


>> +#ifdef __CAN_DEBUG
>> +#define __can_debug(fmt, args...) printk(KERN_DEBUG "can_debug: " fmt, 
>> ## args)
>> +#else
>> +#define __can_debug(fmt, args...)
>> +#endif
>> +#define __can_err(fmt, args...) printk(KERN_ERR "can_err: " fmt, ## 
>> args)
>
> Better use the existing dev_dbg() and dev_err() macros that provide the
> same functionality in a more standard way. You already use them in
> some places, as I noticed.
>
> If you don't have a way to pass a meaningful device, you can use
> pr_debug/pr_err.
>
SG - Ok

>> +void omapl_pru_can_rx_wQ(struct work_struct *work)
>> +{
>
> This is only used in the same file, so better make it static.

SG - This is removed, used NAPI as recommended.

>
>> + if (-1 == pru_can_get_intr_status(priv->dev, &priv->can_rx_hndl))
>> + return;
>
> Don't make up your own return values, just use the standard error codes,
> e.g. -EIO or -EAGAIN, whatever fits.

SG - Ok

>
> The more common way to write the comparison would be the other way round,
>
> if (pru_can_get_intr_status(priv->dev, &priv->can_rx_hndl) == -EAGAIN)
> return;
>
> or, simpler
>
> if (pru_can_get_intr_status(priv->dev, &priv->can_rx_hndl))
> return;

SG - Ok

>
>> +irqreturn_t omapl_tx_can_intr(int irq, void *dev_id)
>> +{
>
> This also should be static

SG - Ok

>
>> + for (bit_set = 0; ((priv->can_tx_hndl.u32interruptstatus & 0xFF)
>> + >> bit_set != 0); bit_set++)
>> + ;
>
> bit_set = fls(priv->can_tx_hndl.u32interruptstatus & 0xFF); ?
>

SG - Ok

>> +irqreturn_t omapl_rx_can_intr(int irq, void *dev_id)
>
> static

SG - Ok


>
>> diff --git a/drivers/net/can/da8xx_pruss/pruss_can_api.c 
>> b/drivers/net/can/da8xx_pruss/pruss_can_api.c
>> new file mode 100644
>> index 0000000..2f7438a
>> --- /dev/null
>> +++ b/drivers/net/can/da8xx_pruss/pruss_can_api.c
>
> A lot of code in this file seems to be unused. Is that right?
> I would suggest adding only the code that is actually being
> used. If you add more functionality later, you can always
> add back the low-level functions, but dead code usually
> turns into broken code quickly.
>

SG - Ok

>> +static can_emu_drv_inst gstr_can_inst[ecanmaxinst];
>
> This is global data and probably needs some for of locking

SG - Ok

>
>> +/*
>> + * pru_can_set_brp() Updates the  BRP register of PRU0
>> + * and PRU1 of OMAP L138. This API will be called by the
>> + * Application to updtae the BRP register of PRU0 and PRU1
>> + *
>> + * param u16bitrateprescaler The can bus bitrate
>> + * prescaler value be set
>> + *
>> + * return   SUCCESS or FAILURE
>> + */
>> +s16 pru_can_set_brp(struct device *dev, u16 u16bitrateprescaler)
>> +{
>
> unused.

SG - Ok

>
>> + u32 u32offset;
>> +
>> + if (u16bitrateprescaler > 255) {
>> + return -1;
>> + }
>
> non-standard error code. It also doesn't match the comment, which
> claims it is SUCCESS or FAILURE, both of which are (rightfully)
> not defined.

SG - Ok

>
>> + u32offset = (PRU_CAN_RX_CLOCK_BRP_REGISTER);
>> + pruss_writel(dev, u32offset, (u32 *) &u16bitrateprescaler, 1);
>> +
>> + u32offset = (PRU_CAN_TX_CLOCK_BRP_REGISTER);
>> + pruss_writel(dev, u32offset, (u32 *) &u16bitrateprescaler, 1);
>

SG - Ok


> You pass a 32 bit pointer to a 16 bit local variable here.
> This has an undefined effect, and if you build this code on
> a big-endian platform, it cannot possibly do anything good.
>
> pruss_writel() is defined in a funny way if it takes a thirty-two bit
> input argument by reference, rather than by value. What is going
> on there?
>
>> +s16 pru_can_set_bit_timing(struct device *dev,
>> + can_bit_timing_consts *pstrbittiming)
>
> unused.
>

SG - Ok


>> + u32 u32offset;
>> + u32 u32serregister;
>
> It's a bit silly to put the name of the type into the name
> of a variable. You already spell it out in the definition.

SG - Ok

>
>> +s16 pru_can_write_data_to_mailbox(struct device *dev,
>> + can_emu_app_hndl *pstremuapphndl)
>> +{
>> + s16 s16subrtnretval;
>> + u32 u32offset;
>> +
>> + if (pstremuapphndl == NULL) {
>> + return -1;
>> + }
>
> nonstandard error code. Also, why the heck is type function
> return type s16 when the only possible return values are 0
> and -1? Just make this an int.

SG - Ok

>
>> + switch ((u8) pstremuapphndl->ecanmailboxnumber) {
>> + case 0:
>> + u32offset = (PRU_CAN_TX_MAILBOX0);
>> + break;
>> + case 1:
>> + u32offset = (PRU_CAN_TX_MAILBOX1);
>> + break;
>> + case 2:
>> + u32offset = (PRU_CAN_TX_MAILBOX2);
>> + break;
>> + case 3:
>> + u32offset = (PRU_CAN_TX_MAILBOX3);
>> + break;
>> + case 4:
>> + u32offset = (PRU_CAN_TX_MAILBOX4);
>> + break;
>> + case 5:
>> + u32offset = (PRU_CAN_TX_MAILBOX5);
>> + break;
>> + case 6:
>> + u32offset = (PRU_CAN_TX_MAILBOX6);
>> + break;
>> + case 7:
>> + u32offset = (PRU_CAN_TX_MAILBOX7);
>> + break;
>> + default:
>> + return -1;
>> + }
>
> Lovely switch statement. I'm sure you find a better way to express this 
> ;-)

SG - Ok.

>
>> + s16subrtnretval = pruss_writel(dev, u32offset,
>> + (u32 *) &(pstremuapphndl->strcanmailbox), 4);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>> + return 0;
>> +}
>
> return pruss_writel(...) ?

SG - Ok.

>
>> +
>> +/*
>> + * pru_can_get_intr_status()
>> + * Gets the interrupts status register value.
>> + * This API will be called by the Application
>> + * to get the interrupts status register value
>> + *
>> + * param  u8prunumber PRU number for which IntStatusReg
>> + * has to be read
>> + *
>> + * return   SUCCESS or FAILURE
>> + */
>> +s16 pru_can_get_intr_status(struct device *dev,
>> + can_emu_app_hndl *pstremuapphndl)
>> +{
>> + u32 u32offset;
>> + s16 s16subrtnretval = -1;
>> +
>> + if (pstremuapphndl == NULL) {
>> + return -1;
>> + }
>
> In every function you check that pstremuapphndl is present. This seems
> rather pointless. How about just making sure you never pass a NULL
> value to these functions? That should not be hard at all from the
> high-level driver.

SG - OK.


>
>> + if (pstremuapphndl->u8prunumber == DA8XX_PRUCORE_1) {
>> + u32offset = (PRU_CAN_TX_INTERRUPT_STATUS_REGISTER);
>> + } else if (pstremuapphndl->u8prunumber == DA8XX_PRUCORE_0) {
>> + u32offset = (PRU_CAN_RX_INTERRUPT_STATUS_REGISTER);
>> + } else {
>> + return -1;
>> + }
>> +
>> + s16subrtnretval = pruss_readl(dev, u32offset,
>> + (u32 *) &pstremuapphndl->u32interruptstatus, 1);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>
> You can also get rid of all these {} braces around one-line statements.

SG - OK.

>
>> +/*
>> + * pru_can_get_mailbox_status() Gets the mailbox status
>> + * register value. This API will be called by the Application
>> + * to get the mailbox status register value
>> + *
>> + * return   SUCCESS or FAILURE
>> + */
>> +s16 pru_can_get_mailbox_status(struct device *dev,
>> + can_emu_app_hndl *pstremuapphndl)
>
> unused
.
SG - OK.

>
>> +/*
>> + * pru_can_config_mode_set() Sets the timing value
>> + * for data transfer. This API will be called by the Application
>> + * to set timing valus for data transfer
>> + *
>> + * return   SUCCESS or FAILURE
>> + */
>> +s16 pru_can_config_mode_set(struct device *dev, bool bconfigmodeflag)
>
> unused.

SG - OK.

>
>> + u32offset = (PRU_CAN_TX_GLOBAL_CONTROL_REGISTER & 0xFFFF);
>> + u32value = 0x00000000;
>> + s16subrtnretval = pruss_writel(dev, u32offset, (u32 *) &u32value, 1);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>> +
>> + u32offset = (PRU_CAN_TX_GLOBAL_STATUS_REGISTER & 0xFFFF);
>> + u32value = 0x00000040;
>> + s16subrtnretval = pruss_writel(dev, u32offset, (u32 *) &u32value, 1);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>> + u32offset = (PRU_CAN_RX_GLOBAL_STATUS_REGISTER & 0xFFFF);
>> + u32value = 0x00000040;
>> + s16subrtnretval = pruss_writel(dev, u32offset, (u32 *) &u32value, 1);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>
> <skipping 50 (!) more of these>
>
> After the third time of writing the same code, you should have noticed 
> that
> there is some duplication involved that can trivially be reduced. A good
> way to express the same would be a table with the contents:
>

SG - OK.
                 Thanks for taking the pain to review this. But, the good 
part is that
                 everything works fine. All this got cluttered as 
development &
                 design changes happened. Hopefully, the cleaned up code 
will
                also work as well :-)

> static struct pru_can_register_init {
> u16 offset;
> u32 value;
> } = {
> { PRU_CAN_TX_GLOBAL_CONTROL_REGISTER, 0, },
> { PRU_CAN_TX_GLOBAL_STATUS_REGISTER, 0x40, },
> { PRU_CAN_RX_GLOBAL_STATUS_REGISTER, 0x40, },
> ...
> };
>
>
>> +
>> +
>> +/*
>> + * pru_can_emu_open() Opens the can emu for
>> + * application to use. This API will be called by the Application
>> + * to Open the can emu for application to use.
>> + *
>> + * param pstremuapphndl Pointer to application handler
>> + * structure
>> + *
>> + * return   SUCCESS or FAILURE
>> + */
>> +s16 pru_can_emu_open(struct device *dev, can_emu_app_hndl 
>> *pstremuapphndl)
>
> unused.

SG - OK.

>
>> +/*
>> + * brief    pru_can_emu_close() Closes the can emu for other
>> + * applications to use. This API will be called by the Application to 
>> Close
>> + * the can emu for other applications to use
>> + *
>> + * param pstremuapphndl Pointer to application handler structure
>> + *
>> + * return   SUCCESS or FAILURE
>> + */
>> +s16 pru_can_emu_close(struct device *dev, can_emu_app_hndl 
>> *pstremuapphndl)
>
> unused

SG - OK.

>
>> +s16 pru_can_emu_sreset(struct device *dev)
>> +{
>> + return 0;
>> +}
>
> pointless.

SG - OK.

>
>> +s16 pru_can_tx(struct device *dev, u8 u8mailboxnumber, u8 u8prunumber)
>> +{
>> + u32 u32offset = 0;
>> + u32 u32value = 0;
>> + s16 s16subrtnretval = -1;
>> +
>> + if (DA8XX_PRUCORE_1 == u8prunumber) {
>> + switch (u8mailboxnumber) {
>> + case 0:
>> + u32offset = (PRU_CAN_TX_MAILBOX0_STATUS_REGISTER & 0xFFFF);
>> + u32value = 0x00000080;
>> + s16subrtnretval = pruss_writel(dev, u32offset,
>> + (u32 *) &u32value, 1);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>> + break;
>> + case 1:
>> + u32offset = (PRU_CAN_TX_MAILBOX1_STATUS_REGISTER & 0xFFFF);
>> + u32value = 0x00000080;
>> + s16subrtnretval = pruss_writel(dev, u32offset,
>> + (u32 *) &u32value, 1);
>> + if (s16subrtnretval == -1) {
>> + return -1;
>> + }
>> + break;
>> + case 2:
>> + u32offset = (PRU_CAN_TX_MAILBOX2_STATUS_REGISTER & 0xFFFF);
>
> Another pointless switch statement.

SG - OK.

>
>> +s16 pru_can_mask_ints(struct device *dev, u32 int_mask)
>> +{
>> + return 0;
>> +}
>> +
>> +int pru_can_get_error_cnt(struct device *dev, u8 u8prunumber)
>> +{
>> + return 0;
>> +}
>
> useless.

SG - OK.

>
>> +int pru_can_get_intc_status(struct device *dev)
>> +{
>> + u32 u32offset = 0;
>> + u32 u32getvalue = 0;
>> + u32 u32clrvalue = 0;
>> +
>> + u32offset = (PRUSS_INTC_STATCLRINT1 & 0xFFFF);
>> + pruss_readl(dev, u32offset, (u32 *) &u32getvalue, 1);
>> +
>> + if (u32getvalue & 4)
>> + u32clrvalue = 34; /* CLR Event 34 */
>> +
>> + if (u32getvalue & 2)
>> + u32clrvalue = 33; /* CLR Event 33  */
>> +
>> + if (u32clrvalue) {
>> + u32offset = (PRUSS_INTC_STATIDXCLR & 0xFFFF);
>> + pruss_writel(dev, u32offset, &u32clrvalue, 1);
>> + } else
>> + return -1;
>
> Could the controller signal both event 34 and 33 simultaneously?
> The only user of this function looks at the individual bits
> of the return value again, which looks wrong for all possible
> return values here.
>

SG - OK. The System Events are mapped to 10 host interrupts (PRU to 
ARM/DSP),
                   as I our case two system events can be mapped to a single 
host interrupt.


>> +#ifndef _PRU_CAN_API_H_
>> +#define CAN_BIT_TIMINGS (0x273)
>> +
>> +/* Timer Clock is sourced from DDR freq (PLL1 SYS CLK 2) */
>> +#define TIMER_CLK_FREQ 132000000
>> +
>> +#define TIMER_SETUP_DELAY 14
>> +#define GPIO_SETUP_DELAY 150
>> +
>> +#define CAN_RX_PRU_0 PRUSS_NUM0
>> +#define CAN_TX_PRU_1 PRUSS_NUM1
>> +
>> +/* Number of Instruction in the Delay loop */
>> +#define DELAY_LOOP_LENGTH 2
>> +
>> +#define PRU1_BASE_ADDR 0x2000
>> +
>> +#define PRU_CAN_TX_GLOBAL_CONTROL_REGISTER (PRU1_BASE_ADDR)
>> +#define PRU_CAN_TX_GLOBAL_STATUS_REGISTER (PRU1_BASE_ADDR + 0x04)
>> +#define PRU_CAN_TX_INTERRUPT_MASK_REGISTER (PRU1_BASE_ADDR + 0x08)
>> +#define PRU_CAN_TX_INTERRUPT_STATUS_REGISTER (PRU1_BASE_ADDR + 0x0C)
>> +#define PRU_CAN_TX_MAILBOX0_STATUS_REGISTER (PRU1_BASE_ADDR + 0x10)
>> +#define PRU_CAN_TX_MAILBOX1_STATUS_REGISTER (PRU1_BASE_ADDR + 0x14)
>
> The header file should be used for interfaces between the two .c files,
> don't mix that with hardware specific definitions. Sometimes you may want
> to have register number lists in a header, if that list is going to be
> used in multiple places. In this case, there is just one user, so better
> move all those definitions over there.

SG - OK.

>
>> +typedef enum {
>> + ecaninst0 = 0,
>> + ecaninst1,
>> + ecanmaxinst
>> +} can_instance_enum;
>> +
>> +typedef enum {
>> + ecanmailbox0 = 0,
>> + ecanmailbox1,
>> + ecanmailbox2,
>> + ecanmailbox3,
>> + ecanmailbox4,
>> + ecanmailbox5,
>> + ecanmailbox6,
>> + ecanmailbox7
>> +} can_mailbox_number;
>> +
>> +typedef enum {
>> + ecandirectioninit = 0,
>> + ecantransmit,
>> + ecanreceive
>> +} can_transfer_direction;
>
> The values are all unused, you only use the typedefs.
> IMHO it would be more sensible to just pass these as unsigned int
> or u32 values, but if you prefer, there is no reason to just do
>
> typedef u32 can_mailbox_number;
>
> etc.

SG - OK.

>
>> +typedef struct {
>> + u16 u16extendedidentifier;
>> + u16 u16baseidentifier;
>> + u8 u8data7;
>> + u8 u8data6;
>> + u8 u8data5;
>> + u8 u8data4;
>> + u8 u8data3;
>> + u8 u8data2;
>> + u8 u8data1;
>> + u8 u8data0;
>> + u16 u16datalength;
>> + u16 u16crc;
>> +} can_mail_box_structure;
>
> Please don't use typedef for complex data structures, and learn about
> better naming of identifiers. I would suggest writing this as
>
> struct pru_can_mailbox {
> u16 ext_id;
> u16 base_id;
> u8 data[8]; /* note: reverse order */
> u16 len;
> u16 crc;
> };
>
> Sames rules apply to the other structures.

SG - OK.

>
> Arnd 

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