On Sat, May 01, 2021 at 09:51:35PM +0200, Lukas Wunner wrote: > On Fri, Apr 23, 2021 at 05:20:55PM +0100, Mark Brown wrote: > > Part of the issue here is that there has been some variation in how > > num_chipselect is interpreted with regard to GPIO based chip selects > > over time. It *should* be redundant, I'm not clear why it's in the > > generic bindings at all but that's lost to history AFAICT. > It seems num_chipselect is meant to be set to the maximum number of > *native* chipselects supported by the controller. Which is overwritten > if GPIO chipselects are used. This gets fun with the controllers that have for various reasons open coded some or all of the GPIO chip select handling. > I failed to appreciate that when I changed num_chipselects for > spi-bcm2835.c with commit 571e31fa60b3. That single line change > in the commit ought to be reverted. > And the kernel-doc ought to be amended because the crucial detail > that num_chipselect needs to be set to the maximum *native* chipselects > isn't mentioned anywhere. Can you send patches for these please? > > The best thing would be to have it not have a single array of chip > > select specific data and instead store everything in the controller_data > > that's there per-device. > Unfortunately that's non-trivial. The slave-specific data is DMA-mapped. > It could be DMA-mapped in ->setup but there's no ->unsetup to DMA-unmap > the memory once the slave is removed. Note that the slave could be removed > dynamically with a DT overlay, not just when the controller is unbound. > So we'd need a new ->unsetup hook at the very least to make this work. There's the cleanup() callback which seems to fit?
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