Brian Norris <briannorris@xxxxxxxxxxxx> wrote: > The DIAG copy engine is only used via polling, but it holds a spinlock > with softirqs disabled. Each iteration of our read/write loops can > theoretically take 20ms (two 10ms timeout loops), and this loop can be > run an unbounded number of times while holding the spinlock -- dependent > on the request size given by the caller. > > As of commit 39501ea64116 ("ath10k: download firmware via diag Copy > Engine for QCA6174 and QCA9377."), we transfer large chunks of firmware > memory using this mechanism. With large enough firmware segments, this > becomes an exceedingly long period for disabling soft IRQs. For example, > with a 500KiB firmware segment, in testing QCA6174A, I see 200 loop > iterations of about 50-100us each, which can total about 10-20ms. > > In reality, we don't really need to block softirqs for this duration. > The DIAG CE is only used in polling mode, and we only need to hold > ce_lock to make sure any CE bookkeeping is done without screwing up > another CE. Otherwise, we only need to ensure exclusion between > ath10k_pci_diag_{read,write}_mem() contexts. > > This patch moves to use fine-grained locking for the shared ce_lock, > while adding a new mutex just to ensure mutual exclusion of diag > read/write operations. > > Tested on QCA6174A, firmware version WLAN.RM.4.4.1-00132-QCARMSWPZ-1. > > Fixes: 39501ea64116 ("ath10k: download firmware via diag Copy Engine for QCA6174 and QCA9377.") > Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx> > Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx> Patch applied to ath-next branch of ath.git, thanks. 25733c4e67df ath10k: pci: use mutex for diagnostic window CE polling -- https://patchwork.kernel.org/patch/10800343/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches