| Message ID | 1409816849.4246.34.camel@pasglop (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04.09.2014 16:47, Benjamin Herrenschmidt wrote: > On all current cache coherent powerpc processors, it is not legit > to map system memory non-cachable. This will cause aliases with > the linear mapping which can be fatal. > > The TTM should generally avoid it after Jerome placement patches but > let's add a sanity check anyway to catch any possible remaining issue. > > Signed-off-by: Benjamin Herrenschmidt <benh@palm4.ozlabs.ibm.com> [...] > @@ -498,6 +501,20 @@ pgprot_t ttm_io_prot(uint32_t caching_flags, pgprot_t tmp) > tmp = pgprot_noncached(tmp); > > #endif > +#if defined(__powerpc__) && !defined(CONFIG_NOT_COHERENT_CACHE) > + /* > + * Using a non-cachable mapping of system memory on > + * cache coherent powerpc's can be fatal, let's make > + * sure this doesn't happen and warn if it does. The > + * only exception is powermac with AGP which has to > + * take the risk. > + */ > + if (!machine_is(powermac) && > + ((caching_flags & TTM_PL_FLAG_SYSTEM) || > + (caching_flags & TTM_PL_FLAG_TT))) { > + pr_err_once("TTM: Attempt to use a non-cached" > + " mapping on RAM unsupported !\n"); > + return tmp; NAK, this breaks AGP on PowerMacs.
On Thu, 2014-09-04 at 16:52 +0900, Michel Dänzer wrote: > > #endif > > +#if defined(__powerpc__) && !defined(CONFIG_NOT_COHERENT_CACHE) > > + /* > > + * Using a non-cachable mapping of system memory on > > + * cache coherent powerpc's can be fatal, let's make > > + * sure this doesn't happen and warn if it does. The > > + * only exception is powermac with AGP which has to > > + * take the risk. > > + */ > > + if (!machine_is(powermac) && > > + ((caching_flags & TTM_PL_FLAG_SYSTEM) || > > + (caching_flags & TTM_PL_FLAG_TT))) { > > + pr_err_once("TTM: Attempt to use a non-cached" > > + " mapping on RAM unsupported !\n"); > > + return tmp; > > NAK, this breaks AGP on PowerMacs. No it doesn't :-) Cheers, Ben.
On 04.09.2014 18:34, Benjamin Herrenschmidt wrote: > On Thu, 2014-09-04 at 16:52 +0900, Michel Dänzer wrote: >>> #endif >>> +#if defined(__powerpc__) && !defined(CONFIG_NOT_COHERENT_CACHE) >>> + /* >>> + * Using a non-cachable mapping of system memory on >>> + * cache coherent powerpc's can be fatal, let's make >>> + * sure this doesn't happen and warn if it does. The >>> + * only exception is powermac with AGP which has to >>> + * take the risk. >>> + */ >>> + if (!machine_is(powermac) && >>> + ((caching_flags & TTM_PL_FLAG_SYSTEM) || >>> + (caching_flags & TTM_PL_FLAG_TT))) { >>> + pr_err_once("TTM: Attempt to use a non-cached" >>> + " mapping on RAM unsupported !\n"); >>> + return tmp; >> >> NAK, this breaks AGP on PowerMacs. > > No it doesn't :-) Yeah sorry, I was blind.
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c index ef2ac3c..48095be 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_util.c +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c @@ -37,6 +37,9 @@ #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/module.h> +#if defined(__powerpc__) +#include <asm/machdep.h> +#endif void ttm_bo_free_old_node(struct ttm_buffer_object *bo) { @@ -498,6 +501,20 @@ pgprot_t ttm_io_prot(uint32_t caching_flags, pgprot_t tmp) tmp = pgprot_noncached(tmp); #endif +#if defined(__powerpc__) && !defined(CONFIG_NOT_COHERENT_CACHE) + /* + * Using a non-cachable mapping of system memory on + * cache coherent powerpc's can be fatal, let's make + * sure this doesn't happen and warn if it does. The + * only exception is powermac with AGP which has to + * take the risk. + */ + if (!machine_is(powermac) && + ((caching_flags & TTM_PL_FLAG_SYSTEM) || + (caching_flags & TTM_PL_FLAG_TT))) { + pr_err_once("TTM: Attempt to use a non-cached" + " mapping on RAM unsupported !\n"); + return tmp; } #endif #if defined(__ia64__) || defined(__arm__) || defined(__powerpc__)
On all current cache coherent powerpc processors, it is not legit to map system memory non-cachable. This will cause aliases with the linear mapping which can be fatal. The TTM should generally avoid it after Jerome placement patches but let's add a sanity check anyway to catch any possible remaining issue. Signed-off-by: Benjamin Herrenschmidt <benh@palm4.ozlabs.ibm.com> --- drivers/gpu/drm/ttm/ttm_bo_util.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)