[3/4] pata_parport: add custom version of wait_after_reset

  Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
bogus values when there's no master device present. This can cause
reset to fail, preventing the lone slave device (such as EXP Computer
CD-865) from working.

Add custom version of wait_after_reset that ignores master failure when
a slave device is present. The custom version is also needed because
the generic ata_sff_wait_after_reset uses direct port I/O for slave
device detection.

Signed-off-by: Ondrej Zary <linux@zary.sk>
---
 drivers/ata/pata_parport/pata_parport.c | 65 ++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 1 deletion(-)
  

On 9/30/23 10:15 PM, Ondrej Zary wrote:

> Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
> bogus values when there's no master device present. This can cause
> reset to fail, preventing the lone slave device (such as EXP Computer
> CD-865) from working.
> 
> Add custom version of wait_after_reset that ignores master failure when
> a slave device is present. The custom version is also needed because
> the generic ata_sff_wait_after_reset uses direct port I/O for slave
> device detection.
> 
> Signed-off-by: Ondrej Zary <linux@zary.sk>
> ---
>  drivers/ata/pata_parport/pata_parport.c | 65 ++++++++++++++++++++++++-
>  1 file changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
> index cf87bbb52f1f..b3db953e615a 100644
> --- a/drivers/ata/pata_parport/pata_parport.c
> +++ b/drivers/ata/pata_parport/pata_parport.c
> @@ -80,6 +80,69 @@ static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
>  	return (nsect == 0x55) && (lbal == 0xaa);
>  }
>  
> +static int pata_parport_wait_after_reset(struct ata_link *link,
> +					 unsigned int devmask,
> +					 unsigned long deadline)
> +{
> +	struct ata_port *ap = link->ap;
> +	struct pi_adapter *pi = ap->host->private_data;
> +	unsigned int dev0 = devmask & (1 << 0);
> +	unsigned int dev1 = devmask & (1 << 1);
> +	int rc, ret = 0;
> +
> +	ata_msleep(ap, ATA_WAIT_AFTER_RESET);
> +
> +	/* always check readiness of the master device */
> +	rc = ata_sff_wait_ready(link, deadline);
> +	/* some adapters return bogus values if master device is not present,

   The multiline comments should start with /* on its own line.
   Have you run scripts/checkpatch.pl on the patches?

> +	 * so don't abort now if a slave device is present
> +	 */
> +	if (rc) {
> +		if (!dev1)
> +			return rc;
> +		ret = -ENODEV;
> +	}
> +
> +	/* if device 1 was found in ata_devchk, wait for register

   Likewise here...

> +	 * access briefly, then wait for BSY to clear.
> +	 */
> +	if (dev1) {
> +		int i;
> +
> +		pata_parport_dev_select(ap, 1);
> +
> +		/* Wait for register access.  Some ATAPI devices fail

   And here...

[...]

MBR, Sergey
  

On 10/1/23 04:15, Ondrej Zary wrote:
> Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
> bogus values when there's no master device present. This can cause
> reset to fail, preventing the lone slave device (such as EXP Computer
> CD-865) from working.
> 
> Add custom version of wait_after_reset that ignores master failure when
> a slave device is present. The custom version is also needed because
> the generic ata_sff_wait_after_reset uses direct port I/O for slave
> device detection.
> 
> Signed-off-by: Ondrej Zary <linux@zary.sk>
> ---
>  drivers/ata/pata_parport/pata_parport.c | 65 ++++++++++++++++++++++++-
>  1 file changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
> index cf87bbb52f1f..b3db953e615a 100644
> --- a/drivers/ata/pata_parport/pata_parport.c
> +++ b/drivers/ata/pata_parport/pata_parport.c
> @@ -80,6 +80,69 @@ static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
>  	return (nsect == 0x55) && (lbal == 0xaa);
>  }
>  
> +static int pata_parport_wait_after_reset(struct ata_link *link,
> +					 unsigned int devmask,
> +					 unsigned long deadline)
> +{
> +	struct ata_port *ap = link->ap;
> +	struct pi_adapter *pi = ap->host->private_data;
> +	unsigned int dev0 = devmask & (1 << 0);
> +	unsigned int dev1 = devmask & (1 << 1);
> +	int rc, ret = 0;
> +
> +	ata_msleep(ap, ATA_WAIT_AFTER_RESET);
> +
> +	/* always check readiness of the master device */
> +	rc = ata_sff_wait_ready(link, deadline);
> +	/* some adapters return bogus values if master device is not present,
> +	 * so don't abort now if a slave device is present
> +	 */

In addition to Sergey's comment, please move this comment inside the "if", or
even better, merge it with the otherwise not very useful "always check
readiness..." comment.

> +	if (rc) {
> +		if (!dev1)
> +			return rc;
> +		ret = -ENODEV;
> +	}
> +
> +	/* if device 1 was found in ata_devchk, wait for register
> +	 * access briefly, then wait for BSY to clear.
> +	 */
> +	if (dev1) {
> +		int i;
> +
> +		pata_parport_dev_select(ap, 1);
> +
> +		/* Wait for register access.  Some ATAPI devices fail
> +		 * to set nsect/lbal after reset, so don't waste too
> +		 * much time on it.  We're gonna wait for !BSY anyway.
> +		 */
> +		for (i = 0; i < 2; i++) {
> +			u8 nsect, lbal;
> +
> +			nsect = pi->proto->read_regr(pi, 0, ATA_REG_NSECT);
> +			lbal = pi->proto->read_regr(pi, 0, ATA_REG_LBAL);
> +			if ((nsect == 1) && (lbal == 1))
> +				break;
> +			ata_msleep(ap, 50);	/* give drive a breather */

Please move the comment on its own line above the sleep call.

> +		}
> +
> +		rc = ata_sff_wait_ready(link, deadline);
> +		if (rc) {
> +			if (rc != -ENODEV)
> +				return rc;
> +			ret = rc;
> +		}
> +	}
> +
> +	/* is all this really necessary? */

I don't know. It is your driver... So either drop this comment, or clearly
explain why this is done.

> +	pata_parport_dev_select(ap, 0);
> +	if (dev1)
> +		pata_parport_dev_select(ap, 1);
> +	if (dev0)
> +		pata_parport_dev_select(ap, 0);

Can you have dev1 && dev0 == true ? This seems like the second if should be an
"else if", but it is not clear what this is doing.

> +
> +	return ret;
> +}
> +
>  static int pata_parport_bus_softreset(struct ata_port *ap, unsigned int devmask,
>  				      unsigned long deadline)
>  {
> @@ -94,7 +157,7 @@ static int pata_parport_bus_softreset(struct ata_port *ap, unsigned int devmask,
>  	ap->last_ctl = ap->ctl;
>  
>  	/* wait the port to become ready */
> -	return ata_sff_wait_after_reset(&ap->link, devmask, deadline);
> +	return pata_parport_wait_after_reset(&ap->link, devmask, deadline);
>  }
>  
>  static int pata_parport_softreset(struct ata_link *link, unsigned int *classes,
  

On 10/3/23 3:55 AM, Damien Le Moal wrote:

[...]
>> Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
>> bogus values when there's no master device present. This can cause
>> reset to fail, preventing the lone slave device (such as EXP Computer
>> CD-865) from working.
>>
>> Add custom version of wait_after_reset that ignores master failure when
>> a slave device is present. The custom version is also needed because
>> the generic ata_sff_wait_after_reset uses direct port I/O for slave
>> device detection.
>>
>> Signed-off-by: Ondrej Zary <linux@zary.sk>
>> ---
>>  drivers/ata/pata_parport/pata_parport.c | 65 ++++++++++++++++++++++++-
>>  1 file changed, 64 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
>> index cf87bbb52f1f..b3db953e615a 100644
>> --- a/drivers/ata/pata_parport/pata_parport.c
>> +++ b/drivers/ata/pata_parport/pata_parport.c
>> @@ -80,6 +80,69 @@ static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
>>  	return (nsect == 0x55) && (lbal == 0xaa);
>>  }
>>  
>> +static int pata_parport_wait_after_reset(struct ata_link *link,
>> +					 unsigned int devmask,
>> +					 unsigned long deadline)
>> +{
>> +	struct ata_port *ap = link->ap;
>> +	struct pi_adapter *pi = ap->host->private_data;
>> +	unsigned int dev0 = devmask & (1 << 0);
>> +	unsigned int dev1 = devmask & (1 << 1);
>> +	int rc, ret = 0;
>> +
>> +	ata_msleep(ap, ATA_WAIT_AFTER_RESET);
>> +
>> +	/* always check readiness of the master device */
>> +	rc = ata_sff_wait_ready(link, deadline);
>> +	/* some adapters return bogus values if master device is not present,
>> +	 * so don't abort now if a slave device is present
>> +	 */
> 
> In addition to Sergey's comment, please move this comment inside the "if", or
> even better, merge it with the otherwise not very useful "always check
> readiness..." comment.

   That comment was copied from ata_sff_wait_after_reset(), I think...

[...]
>> +	/* if device 1 was found in ata_devchk, wait for register
>> +	 * access briefly, then wait for BSY to clear.
>> +	 */
>> +	if (dev1) {
>> +		int i;
>> +
>> +		pata_parport_dev_select(ap, 1);
>> +
>> +		/* Wait for register access.  Some ATAPI devices fail
>> +		 * to set nsect/lbal after reset, so don't waste too
>> +		 * much time on it.  We're gonna wait for !BSY anyway.
>> +		 */
>> +		for (i = 0; i < 2; i++) {
>> +			u8 nsect, lbal;
>> +
>> +			nsect = pi->proto->read_regr(pi, 0, ATA_REG_NSECT);
>> +			lbal = pi->proto->read_regr(pi, 0, ATA_REG_LBAL);
>> +			if ((nsect == 1) && (lbal == 1))
>> +				break;
>> +			ata_msleep(ap, 50);	/* give drive a breather */
> 
> Please move the comment on its own line above the sleep call.

   Again, copied verbatim from ata_sff_wait_after_reset()...

>> +		}
>> +
>> +		rc = ata_sff_wait_ready(link, deadline);
>> +		if (rc) {
>> +			if (rc != -ENODEV)
>> +				return rc;
>> +			ret = rc;
>> +		}
>> +	}
>> +
>> +	/* is all this really necessary? */
> 
> I don't know. It is your driver... So either drop this comment, or clearly
> explain why this is done.

   And again, copied verbatim from ata_sff_wait_after_reset()...

>> +	pata_parport_dev_select(ap, 0);
>> +	if (dev1)
>> +		pata_parport_dev_select(ap, 1);
>> +	if (dev0)
>> +		pata_parport_dev_select(ap, 0);
> 
> Can you have dev1 && dev0 == true ? This seems like the second if should be an
> "else if", but it is not clear what this is doing.

   I guess this tries to leave the valid taskfile regs readable on a channel, instead
of just 0xff...

[...]

MBR, Sergey
  

On Monday 02 October 2023 22:48:59 Sergey Shtylyov wrote:
> On 9/30/23 10:15 PM, Ondrej Zary wrote:
> 
> > Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
> > bogus values when there's no master device present. This can cause
> > reset to fail, preventing the lone slave device (such as EXP Computer
> > CD-865) from working.
> > 
> > Add custom version of wait_after_reset that ignores master failure when
> > a slave device is present. The custom version is also needed because
> > the generic ata_sff_wait_after_reset uses direct port I/O for slave
> > device detection.
> > 
> > Signed-off-by: Ondrej Zary <linux@zary.sk>
> > ---
> >  drivers/ata/pata_parport/pata_parport.c | 65 ++++++++++++++++++++++++-
> >  1 file changed, 64 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
> > index cf87bbb52f1f..b3db953e615a 100644
> > --- a/drivers/ata/pata_parport/pata_parport.c
> > +++ b/drivers/ata/pata_parport/pata_parport.c
> > @@ -80,6 +80,69 @@ static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
> >  	return (nsect == 0x55) && (lbal == 0xaa);
> >  }
> >  
> > +static int pata_parport_wait_after_reset(struct ata_link *link,
> > +					 unsigned int devmask,
> > +					 unsigned long deadline)
> > +{
> > +	struct ata_port *ap = link->ap;
> > +	struct pi_adapter *pi = ap->host->private_data;
> > +	unsigned int dev0 = devmask & (1 << 0);
> > +	unsigned int dev1 = devmask & (1 << 1);
> > +	int rc, ret = 0;
> > +
> > +	ata_msleep(ap, ATA_WAIT_AFTER_RESET);
> > +
> > +	/* always check readiness of the master device */
> > +	rc = ata_sff_wait_ready(link, deadline);
> > +	/* some adapters return bogus values if master device is not present,
> 
>    The multiline comments should start with /* on its own line.
>    Have you run scripts/checkpatch.pl on the patches?

Checkpatch doesn't complain.

> > +	 * so don't abort now if a slave device is present
> > +	 */
> > +	if (rc) {
> > +		if (!dev1)
> > +			return rc;
> > +		ret = -ENODEV;
> > +	}
> > +
> > +	/* if device 1 was found in ata_devchk, wait for register
> 
>    Likewise here...
> 
> > +	 * access briefly, then wait for BSY to clear.
> > +	 */
> > +	if (dev1) {
> > +		int i;
> > +
> > +		pata_parport_dev_select(ap, 1);
> > +
> > +		/* Wait for register access.  Some ATAPI devices fail
> 
>    And here...
> 
> [...]
> 
> MBR, Sergey
>
  

On 10/4/23 01:55, Sergey Shtylyov wrote:
> On 10/3/23 3:55 AM, Damien Le Moal wrote:
> 
> [...]
>>> Some parallel adapters (e.g. EXP Computer MC-1285B EPP Cable) return
>>> bogus values when there's no master device present. This can cause
>>> reset to fail, preventing the lone slave device (such as EXP Computer
>>> CD-865) from working.
>>>
>>> Add custom version of wait_after_reset that ignores master failure when
>>> a slave device is present. The custom version is also needed because
>>> the generic ata_sff_wait_after_reset uses direct port I/O for slave
>>> device detection.
>>>
>>> Signed-off-by: Ondrej Zary <linux@zary.sk>
>>> ---
>>>  drivers/ata/pata_parport/pata_parport.c | 65 ++++++++++++++++++++++++-
>>>  1 file changed, 64 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
>>> index cf87bbb52f1f..b3db953e615a 100644
>>> --- a/drivers/ata/pata_parport/pata_parport.c
>>> +++ b/drivers/ata/pata_parport/pata_parport.c
>>> @@ -80,6 +80,69 @@ static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
>>>  	return (nsect == 0x55) && (lbal == 0xaa);
>>>  }
>>>  
>>> +static int pata_parport_wait_after_reset(struct ata_link *link,
>>> +					 unsigned int devmask,
>>> +					 unsigned long deadline)
>>> +{
>>> +	struct ata_port *ap = link->ap;
>>> +	struct pi_adapter *pi = ap->host->private_data;
>>> +	unsigned int dev0 = devmask & (1 << 0);
>>> +	unsigned int dev1 = devmask & (1 << 1);
>>> +	int rc, ret = 0;
>>> +
>>> +	ata_msleep(ap, ATA_WAIT_AFTER_RESET);
>>> +
>>> +	/* always check readiness of the master device */
>>> +	rc = ata_sff_wait_ready(link, deadline);
>>> +	/* some adapters return bogus values if master device is not present,
>>> +	 * so don't abort now if a slave device is present
>>> +	 */
>>
>> In addition to Sergey's comment, please move this comment inside the "if", or
>> even better, merge it with the otherwise not very useful "always check
>> readiness..." comment.
> 
>    That comment was copied from ata_sff_wait_after_reset(), I think...

Even if that is the case. let's not copy bad stuff as is but rather improve it.