tree ddd30f9c1cc1ffc9e4f9e1fcb3fe4abc53d2b121
parent 75b3cb97eb1f05042745c0655a7145b0262d4c5c
author Mark Brown <broonie@kernel.org> 1633699917 +0100
committer Mark Brown <broonie@kernel.org> 1634212049 +0100
gpgsig -----BEGIN PGP SIGNATURE-----
 
 iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmFoGNEACgkQJNaLcl1U
 h9CsGgf/WH2tcFODc/EOzm/daNV3p0OP2vk8h97cRYx26LLU5ofodGHQeDdYu1es
 6B2pdrBJgKa46b+TWmbuc15tdxxp2g5gXWaBHZX7Ggi+jQxpyQhOqn46Pvq87y3s
 9YYOZP2e3wGkSQ0d0u5aVb2Omkq6nk/f+E2klXJFVt+GXeeIgdSZnP+1gHJ+xGhA
 xIiJ3FiaWy8S2mXxunF1pW2UHnI+HfZNaAtGfWT8a7aFDfRyDip5egFKL06vOjSh
 kY5YAF7LxNUUb0qTogclSfxUoZ1OBLfOA9znK3gVWMILPTQf/younCxyZEQ5qxWQ
 N1imv6+z5cio0tU4mL7qmK1QnrmoZA==
 =1cWB
 -----END PGP SIGNATURE-----

spi: Fix deadlock when adding SPI controllers on SPI buses

Currently we have a global spi_add_lock which we take when adding new
devices so that we can check that we're not trying to reuse a chip
select that's already controlled.  This means that if the SPI device is
itself a SPI controller and triggers the instantiation of further SPI
devices we trigger a deadlock as we try to register and instantiate
those devices while in the process of doing so for the parent controller
and hence already holding the global spi_add_lock.  Since we only care
about concurrency within a single SPI bus move the lock to be per
controller, avoiding the deadlock.

This can be easily triggered in the case of spi-mux.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>