Hi Pavel,
On Mon, May 10, 2021 at 10:56:50PM +0200, Pavel Machek wrote:
Hi!
From: Bhaumik Bhatt bbhatt@codeaurora.org
commit 47705c08465931923e2f2b506986ca0bdf80380d upstream.
When clearing up the channel context after client drivers are done using channels, the configuration is currently not being reset entirely. Ensure this is done to appropriately handle issues where clients unaware of the context state end up calling functions which expect a context.
+++ b/drivers/bus/mhi/core/init.c @@ -544,6 +544,7 @@ void mhi_deinit_chan_ctxt(struct mhi_con
- u32 tmp;
@@ -554,7 +555,19 @@ void mhi_deinit_chan_ctxt(struct mhi_con
...
- tmp = chan_ctxt->chcfg;
- tmp &= ~CHAN_CTX_CHSTATE_MASK;
- tmp |= (MHI_CH_STATE_DISABLED << CHAN_CTX_CHSTATE_SHIFT);
- chan_ctxt->chcfg = tmp;
- /* Update to all cores */
- smp_wmb();
}
This is really interesting code; author was careful to make sure chcfg is updated atomically, but C compiler is free to undo that. Plus, this will make all kinds of checkers angry.
Does the file need to use READ_ONCE and WRITE_ONCE?
Thanks for looking into this.
I agree that the order could be mangled between chcfg read & write and using READ_ONCE & WRITE_ONCE seems to be a good option.
Bhaumik, can you please submit a patch and tag stable?
Thanks, Mani
Best regards, Pavel -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany