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From:   Ondrej Zary <linux@zary.sk>
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Sergey Shtylyov <s.shtylyov@omp.ru>,
        Jens Axboe <axboe@kernel.dk>, Tim Waugh <tim@cyberelk.net>,
        linux-block@vger.kernel.org, linux-parport@lists.infradead.org,
        linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 3/4] pata_parport: add custom version of wait_after_reset
Date:   Sat, 30 Sep 2023 21:15:10 +0200
Message-Id: <20230930191511.24994-4-linux@zary.sk>
In-Reply-To: <20230930191511.24994-1-linux@zary.sk>
References: <20230930191511.24994-1-linux@zary.sk>
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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
+	 */
+	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 */
+		}
+
+		rc = ata_sff_wait_ready(link, deadline);
+		if (rc) {
+			if (rc != -ENODEV)
+				return rc;
+			ret = rc;
+		}
+	}
+
+	/* is all this really necessary? */
+	pata_parport_dev_select(ap, 0);
+	if (dev1)
+		pata_parport_dev_select(ap, 1);
+	if (dev0)
+		pata_parport_dev_select(ap, 0);
+
+	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,
-- 
Ondrej Zary