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Subject: Re: [PATCH 3/4] ata: pata_parport: add custom version of
 wait_after_reset
To:     Ondrej Zary <linux@zary.sk>, Damien Le Moal <dlemoal@kernel.org>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>
CC:     Christoph Hellwig <hch@lst.de>, Tim Waugh <tim@cyberelk.net>,
        <linux-parport@lists.infradead.org>, <linux-ide@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20231005192440.4047-1-linux@zary.sk>
 <20231005192440.4047-4-linux@zary.sk>
From:   Sergey Shtylyov <s.shtylyov@omp.ru>
Organization: Open Mobile Platform
Message-ID: <16779c89-a23c-9d48-3d87-7783ba44931f@omp.ru>
Date:   Thu, 5 Oct 2023 23:24:11 +0300
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On 10/5/23 10:24 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>

Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>

> ---
>  drivers/ata/pata_parport/pata_parport.c | 67 ++++++++++++++++++++++++-
>  1 file changed, 66 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/pata_parport/pata_parport.c b/drivers/ata/pata_parport/pata_parport.c
> index cf87bbb52f1f..318b2ce2d8d1 100644
> --- a/drivers/ata/pata_parport/pata_parport.c
> +++ b/drivers/ata/pata_parport/pata_parport.c
> @@ -80,6 +80,71 @@ 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);
> +	if (rc) {
> +		/*
> +		 * some adapters return bogus values if master device is not
> +		 * present, so don't abort now if a slave device is present
> +		 */
> +		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);

   I think we do need an empty line here, as in the original function...

> +		/*
> +		 * 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))

   The inner parens not needed here...

[...]

MBR, Sergey