Hello Remi, On Wed, 22 May 2019 23:33:51 +0200 Remi Pommarel <repk@xxxxxxxxxxxx> wrote: > Aardvark's PCI_EXP_LNKSTA_LT flag in its link status register is not > implemented and does not reflect the actual link training state (the > flag is always set to 0). In order to support link re-training feature > this flag has to be emulated. The Link Training and Status State > Machine (LTSSM) flag in Aardvark LMI config register could be used as > a link training indicator. Indeed if the LTSSM is in L0 or upper state > then link training has completed (see [1]). > > Unfortunately because after asking a link retraining it takes a while > for the LTSSM state to become less than 0x10 (due to L0s to recovery > state transition delays), LTSSM can still be in L0 while link training > has not finished yet. So this waits for link to be in recovery or lesser > state before returning after asking for a link retrain. > > [1] "PCI Express Base Specification", REV. 4.0 > PCI Express, February 19 2014, Table 4-14 > > Signed-off-by: Remi Pommarel <repk@xxxxxxxxxxxx> Here as well, sorry for the very long delay, and many thanks for the great research work, including the arm-trusted-firmware fix. I reviewed the implementation, and tested on my Armada 3720 DB board with a E1000E NIC, and it all looks good to me. Acked-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx> Thanks! Thomas -- Thomas Petazzoni, CTO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
