On Thu, 2024-02-08 at 13:34 -0500, William Breathitt Gray wrote: > On Mon, Feb 05, 2024 at 04:58:14PM +0100, Nuno Sa via B4 Relay wrote: > > From: Nuno Sa <nuno.sa@xxxxxxxxxx> > > > > Aligning to the L1 cache does guarantee the same alignment as kmallocing > > an object [1]. Furthermore, in some platforms, that alignment is not > > sufficient for DMA safety (in case someone wants to have a DMA safe > > buffer in privdata) [2]. > > > > Sometime ago, we had the same fixes in IIO. > > > > [1]: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/devres.c#n35 > > [2]: > > https://lore.kernel.org/linux-iio/20220508175712.647246-2-jic23@xxxxxxxxxx/ > > > > Fixes: c18e2760308e ("counter: Provide alternative counter registration > > functions") > > Signed-off-by: Nuno Sa <nuno.sa@xxxxxxxxxx> > > --- > > William, if you prefer, we can do something like in IIO and add a > > specific COUNTER_DMA_MINALIGN define > > --- > > drivers/counter/counter-core.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c > > index 09c77afb33ca..073bf6b67a57 100644 > > --- a/drivers/counter/counter-core.c > > +++ b/drivers/counter/counter-core.c > > @@ -34,7 +34,7 @@ struct counter_device_allochelper { > > * This is cache line aligned to ensure private data behaves like > > if it > > * were kmalloced separately. > > */ > > - unsigned long privdata[] ____cacheline_aligned; > > + unsigned long privdata[] __aligned(ARCH_DMA_MINALIGN); > > }; > > > > static void counter_device_release(struct device *dev) > > > > --- > > base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d > > change-id: 20240205-counter-align-fix-3faebfb572af > > -- > > > > Thanks! > > - Nuno Sá > > Hi Nunon, > > This change sounds reasonable, but should the comment block above > privdata be updated to reflect the change? > > Hi William, Yeah, maybe. I can spin a new version with that... To be sure, you mean (in the comment) private -> privdata, right? Also realized a typo in the commit message: "Aligning to the L1 cache does guarantee..." - Obviously, I meant "does *not*...". Thanks! - Nuno Sá
