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Message-ID: <828b4e9a-9e1f-a643-7fed-d4d33e8d8d8e@amd.com>
Date:   Fri, 17 Feb 2023 07:49:11 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>, Sanju.Mehta@....com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] thunderbolt: Refactor DROM reading


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@....com>
>> ---
>> 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

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