linux-kernel - [PATCH 1/5] drivers/thunderbolt: Retry DROM reads for more failure scenarios

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Date:   Wed, 2 Mar 2022 16:07:05 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:     "open list:THUNDERBOLT DRIVER" <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <Sanju.Mehta@....com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH 1/5] drivers/thunderbolt: Retry DROM reads for more failure scenarios

Currently DROM reads are only retried in the case that parsing failed.
However if the size or CRC fails, then there should also be a retry.

This helps with reading the DROM on TBT3 devices connected to AMD
Yellow Carp which will sometimes fail on the first attempt.

Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/thunderbolt/eeprom.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
index 470885e6f1c8..10cdbcb55df9 100644
--- a/drivers/thunderbolt/eeprom.c
+++ b/drivers/thunderbolt/eeprom.c
@@ -553,9 +553,9 @@ static int tb_drom_parse(struct tb_switch *sw)
 	crc = tb_crc8((u8 *) &header->uid, 8);
 	if (crc != header->uid_crc8) {
 		tb_sw_warn(sw,
-			"DROM UID CRC8 mismatch (expected: %#x, got: %#x), aborting\n",
+			"DROM UID CRC8 mismatch (expected: %#x, got: %#x)\n",
 			header->uid_crc8, crc);
-		return -EINVAL;
+		return -EILSEQ;
 	}
 	if (!sw->uid)
 		sw->uid = header->uid;
@@ -654,6 +654,7 @@ int tb_drom_read(struct tb_switch *sw)
 	sw->drom = kzalloc(size, GFP_KERNEL);
 	if (!sw->drom)
 		return -ENOMEM;
+read:
 	res = tb_drom_read_n(sw, 0, sw->drom, size);
 	if (res)
 		goto err;
@@ -662,7 +663,11 @@ int tb_drom_read(struct tb_switch *sw)
 	header = (void *) sw->drom;
 
 	if (header->data_len + TB_DROM_DATA_START != size) {
-		tb_sw_warn(sw, "drom size mismatch, aborting\n");
+		tb_sw_warn(sw, "drom size mismatch\n");
+		if (retries--) {
+			msleep(100);
+			goto read;
+		}
 		goto err;
 	}
 
@@ -683,11 +688,9 @@ int tb_drom_read(struct tb_switch *sw)
 
 	/* If the DROM parsing fails, wait a moment and retry once */
 	if (res == -EILSEQ && retries--) {
-		tb_sw_warn(sw, "parsing DROM failed, retrying\n");
+		tb_sw_warn(sw, "parsing DROM failed\n");
 		msleep(100);
-		res = tb_drom_read_n(sw, 0, sw->drom, size);
-		if (!res)
-			goto parse;
+		goto read;
 	}
 
 	if (!res)
-- 
2.34.1