Some TBT3 devices have a hard time reliably responding to bit banging requests correctly when connected to AMD USB4 hosts running Linux.
These problems are not reported in any other CM, and comparing the implementations the Linux CM is the only one that utilizes bit banging to access the DROM. Other CM implementations access the DROM directly from the NVM instead of bit banging.
Adjust the flow to try this on TBT3 devices before resorting to bit banging.
Cc: stable@vger.kernel.org Signed-off-by: Mario Limonciello mario.limonciello@amd.com --- drivers/thunderbolt/eeprom.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c index c90d22f56d4e1..d9d9567bb938b 100644 --- a/drivers/thunderbolt/eeprom.c +++ b/drivers/thunderbolt/eeprom.c @@ -640,6 +640,10 @@ int tb_drom_read(struct tb_switch *sw) return 0; }
+ /* TBT3 devices have the DROM as part of NVM */ + if (tb_drom_copy_nvm(sw, &size) == 0) + goto parse; + res = tb_drom_read_n(sw, 14, (u8 *) &size, 2); if (res) return res;
Hi,
On Tue, Feb 14, 2023 at 09:46:45AM -0600, Mario Limonciello wrote:
I'm sure Apple CM uses bitbanging because it is what Andreas reverse engineered when he added the initial Linux Thunderbolt support ;-) I guess this is then only Window CM? The problem with reading NVM directly is that we may lose things like UUID, so I'm wondering if there is something else going on.
Can you give some details, like what is the device in question?
On 2/14/23 23:58, Mika Westerberg wrote:
When I say other CMs, maybe I should have specified which ones were checked :)
The following CM get the DROM without bit-banging:
Win11 CM (MS inbox)
Win10 CM (AMD)
Pre-OS CM (AMD)
Can you give some details, like what is the device in question?
It happens with both AR and TR based TBT3 devices connected to AMD USB4 router. It's not any one specific vendor or model, we've seen it across multiple vendors with a failure rate of about 30%.
With an analyzer connected in between we can see that the connected TBT3 device does respond to the bit banging correctly, but the response is not making it over to the USB4 router.
It happens with multiple retimer vendors, but it hasn't been checked on a retimer-less system yet.
I guess something else that might be less detrimental the loss of UUID by reading DROM this way would be to only read DROM this way if any CRC failed.
Hi,
On Wed, Feb 15, 2023 at 12:10:54AM -0600, Mario Limonciello wrote:
Okay that's good to know :) I think you may want to mention this in the commit log too.
I see.
Actually we do read UUID for TBT3 devices from link controller registers (see tb_lc_read_uuid()) instead so I think perhaps we can limit the bitbanging just for older TBT devices with no LC or something like that?
linux-stable-mirror@lists.linaro.org
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Mario Limonciello -
Mika Westerberg