Re: [PATCH v3 3/3] thunderbolt: Refactor DROM reading

From: Mario Limonciello
Date: Fri Feb 17 2023 - 08:49:41 EST


On 2/17/23 07:36, Mika Westerberg wrote:
Hi Mario,

On Thu, Feb 16, 2023 at 02:19:10PM -0600, Mario Limonciello wrote:
The NVM reading code has a series of gotos that potentially introduce
unexpected behaviors with retries if something unexpected has failed
to parse.

Additionally the retry logic introduced in commit f022ff7bf377
("thunderbolt: Retry DROM read once if parsing fails") was added from
failures in bit banging, which aren't expected to be present when the
DROM is fetched directly from the NVM.
Okay that's why you remove the EILSEQ returns below, right?


Yep, that's right.


Refactor the code to remove the gotos and drop the retry logic.
Thanks for doing this.


Sure.


Few minor stylistic comments below. I can also
fix these myself when applying if you prefer.


If there is any other feedback on the other patches in the series from you or anyone else before 6.3-rc1 I'll send out a v4 fixup the style stuff outlined below.

Otherwise, I'll take up your offer thanks for that.


Note I will be on vacation next week but will be picking up patches once
v6.3-rc1 is released.

OK, appreciated.


Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
v2->v3:
* Split out refactor
---
drivers/thunderbolt/eeprom.c | 147 +++++++++++++++++++----------------
1 file changed, 79 insertions(+), 68 deletions(-)

diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
index a326cf16ca3d..2a078c69f0d2 100644
--- a/drivers/thunderbolt/eeprom.c
+++ b/drivers/thunderbolt/eeprom.c
@@ -416,7 +416,7 @@ static int tb_drom_parse_entries(struct tb_switch *sw, size_t header_size)
if (pos + 1 == drom_size || pos + entry->len > drom_size
|| !entry->len) {
tb_sw_warn(sw, "DROM buffer overrun\n");
- return -EILSEQ;
+ return -EIO;
}
switch (entry->type) {
@@ -543,7 +543,37 @@ static int tb_drom_read_n(struct tb_switch *sw, u16 offset, u8 *val,
return tb_eeprom_read_n(sw, offset, val, count);
}
-static int tb_drom_parse(struct tb_switch *sw)
+static int tb_drom_bit_bang(struct tb_switch *sw, u16 *size)
+{
+ int res;
ret

+
+ res = tb_drom_read_n(sw, 14, (u8 *) size, 2);
+ if (res)
+ return res;
empty line here.

+ *size &= 0x3ff;
+ *size += TB_DROM_DATA_START;
here too.

+ tb_sw_dbg(sw, "reading drom (length: %#x)\n", *size);
+ if (*size < sizeof(struct tb_drom_header)) {
+ tb_sw_warn(sw, "drom too small, aborting\n");
DROM

+ return -EIO;
+ }
+
+ sw->drom = kzalloc(*size, GFP_KERNEL);
+ if (!sw->drom)
+ return -ENOMEM;
+
+ res = tb_drom_read_n(sw, 0, sw->drom, *size);
+ if (res)
+ goto err;
+
+ return 0;
empty line

+err:
+ kfree(sw->drom);
+ sw->drom = NULL;
empty line

+ return res;
+}
+
+static int tb_drom_parse_v1(struct tb_switch *sw)
{
const struct tb_drom_header *header =
(const struct tb_drom_header *)sw->drom;
@@ -554,7 +584,7 @@ static int tb_drom_parse(struct tb_switch *sw)
tb_sw_warn(sw,
"DROM UID CRC8 mismatch (expected: %#x, got: %#x)\n",
header->uid_crc8, crc);
- return -EILSEQ;
+ return -EIO;
}
if (!sw->uid)
sw->uid = header->uid;
@@ -588,6 +618,43 @@ static int usb4_drom_parse(struct tb_switch *sw)
return tb_drom_parse_entries(sw, USB4_DROM_HEADER_SIZE);
}
+static int tb_drom_parse(struct tb_switch *sw, u16 *size)
+{
+ struct tb_drom_header *header = (void *) sw->drom;
+ int res;
ret

+
+ if (header->data_len + TB_DROM_DATA_START != *size) {
+ tb_sw_warn(sw, "drom size mismatch\n");
DROM

+ goto err;
+ }
+
+ tb_sw_dbg(sw, "DROM version: %d\n", header->device_rom_revision);
+
+ switch (header->device_rom_revision) {
+ case 3:
+ res = usb4_drom_parse(sw);
+ break;
+ default:
+ tb_sw_warn(sw, "DROM device_rom_revision %#x unknown\n",
+ header->device_rom_revision);
+ fallthrough;
+ case 1:
+ res = tb_drom_parse_v1(sw);
+ break;
+ }
+
+ if (res) {
+ tb_sw_warn(sw, "parsing DROM failed\n");
+ goto err;
+ }
+
+ return 0;
empty line

+err:
+ kfree(sw->drom);
+ sw->drom = NULL;
empty line

+ return -EIO;
+}
+
/**
* tb_drom_read() - Copy DROM to sw->drom and parse it
* @sw: Router whose DROM to read and parse
@@ -601,8 +668,7 @@ static int usb4_drom_parse(struct tb_switch *sw)
int tb_drom_read(struct tb_switch *sw)
{
u16 size;
- struct tb_drom_header *header;
- int res, retries = 1;
+ int res;
if (sw->drom)
return 0;
@@ -613,11 +679,11 @@ int tb_drom_read(struct tb_switch *sw)
* in a device property. Use it if available.
*/
if (tb_drom_copy_efi(sw, &size) == 0)
- goto parse;
+ return tb_drom_parse(sw, &size);
/* Non-Apple hardware has the DROM as part of NVM */
if (tb_drom_copy_nvm(sw, &size) == 0)
- goto parse;
+ return tb_drom_parse(sw, &size);
/*
* USB4 hosts may support reading DROM through router
@@ -626,7 +692,7 @@ int tb_drom_read(struct tb_switch *sw)
if (tb_switch_is_usb4(sw)) {
usb4_switch_read_uid(sw, &sw->uid);
if (!usb4_copy_host_drom(sw, &size))
- goto parse;
+ return tb_drom_parse(sw, &size);
} else {
/*
* The root switch contains only a dummy drom
@@ -640,67 +706,12 @@ int tb_drom_read(struct tb_switch *sw)
}
/* We can use LC to get UUID later */
- if (sw->cap_lc && tb_drom_copy_nvm(sw, &size) == 0)
- goto parse;
-
- res = tb_drom_read_n(sw, 14, (u8 *) &size, 2);
+ if (sw->cap_lc)
+ res = tb_drom_copy_nvm(sw, &size);
+ else
+ res = tb_drom_bit_bang(sw, &size);
if (res)
return res;
- size &= 0x3ff;
- size += TB_DROM_DATA_START;
- tb_sw_dbg(sw, "reading drom (length: %#x)\n", size);
- if (size < sizeof(*header)) {
- tb_sw_warn(sw, "drom too small, aborting\n");
- return -EIO;
- }
-
- 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;
-
-parse:
- header = (void *) sw->drom;
-
- if (header->data_len + TB_DROM_DATA_START != size) {
- tb_sw_warn(sw, "drom size mismatch\n");
- if (retries--) {
- msleep(100);
- goto read;
- }
- goto err;
- }
-
- tb_sw_dbg(sw, "DROM version: %d\n", header->device_rom_revision);
-
- switch (header->device_rom_revision) {
- case 3:
- res = usb4_drom_parse(sw);
- break;
- default:
- tb_sw_warn(sw, "DROM device_rom_revision %#x unknown\n",
- header->device_rom_revision);
- fallthrough;
- case 1:
- res = tb_drom_parse(sw);
- break;
- }
-
- /* If the DROM parsing fails, wait a moment and retry once */
- if (res == -EILSEQ && retries--) {
- tb_sw_warn(sw, "parsing DROM failed\n");
- msleep(100);
- goto read;
- }
- if (!res)
- return 0;
-
-err:
- kfree(sw->drom);
- sw->drom = NULL;
- return -EIO;
+ return tb_drom_parse(sw, &size);
}
--
2.34.1