01.02.2019 16:28, Thierry Reding пишет: > From: Thierry Reding <[email protected]> > > The host1x CDMA push buffer is terminated by a special opcode (RESTART) > that tells the CDMA to wrap around to the beginning of the push buffer. > To accomodate the RESTART opcode, an extra 4 bytes are allocated on top > of the 512 * 8 = 4096 bytes needed for the 512 slots (1 slot = 2 words) > that are used for other commands passed to CDMA. This requires that two > memory pages are allocated, but most of the second page (4092 bytes) is > never used. > > Decrease the number of slots to 511 so that the RESTART opcode fits > within the page. Adjust the push buffer wraparound code to take into > account push buffer sizes that are not a power of two. > > Signed-off-by: Thierry Reding <[email protected]> > --- > drivers/gpu/host1x/cdma.c | 29 +++++++++++++++++++++++++---- > 1 file changed, 25 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/host1x/cdma.c b/drivers/gpu/host1x/cdma.c > index a96c4dd1e449..50c1370b56c7 100644 > --- a/drivers/gpu/host1x/cdma.c > +++ b/drivers/gpu/host1x/cdma.c > @@ -42,7 +42,17 @@ > * means that the push buffer is full, not empty. > */ > > -#define HOST1X_PUSHBUFFER_SLOTS 512 > +/* > + * Typically the commands written into the push buffer are a pair of words. > We > + * use slots to represent each of these pairs and to simplify things. Note > the > + * strange number of slots allocated here. 512 slots will fit exactly within > a > + * single memory page. We also need one additional word at the end of the > push > + * buffer for the RESTART opcode that will instruct the CDMA to jump back to > + * the beginning of the push buffer. With 512 slots, this means that we'll > use > + * 2 memory pages and waste 4092 bytes of the second page that will never be > + * used. > + */ > +#define HOST1X_PUSHBUFFER_SLOTS 511 > > /* > * Clean up push buffer resources > @@ -148,7 +158,10 @@ static void host1x_pushbuffer_push(struct push_buffer > *pb, u32 op1, u32 op2) > WARN_ON(pb->pos == pb->fence); > *(p++) = op1; > *(p++) = op2; > - pb->pos = (pb->pos + 8) & (pb->size - 1); > + pb->pos += 8; > + > + if (pb->pos >= pb->size) > + pb->pos -= pb->size; > } > > /* > @@ -158,7 +171,10 @@ static void host1x_pushbuffer_push(struct push_buffer > *pb, u32 op1, u32 op2) > static void host1x_pushbuffer_pop(struct push_buffer *pb, unsigned int slots) > { > /* Advance the next write position */ > - pb->fence = (pb->fence + slots * 8) & (pb->size - 1); > + pb->fence += slots * 8; > + > + if (pb->fence >= pb->size) > + pb->fence -= pb->size; > } > > /* > @@ -166,7 +182,12 @@ static void host1x_pushbuffer_pop(struct push_buffer > *pb, unsigned int slots) > */ > static u32 host1x_pushbuffer_space(struct push_buffer *pb) > { > - return ((pb->fence - pb->pos) & (pb->size - 1)) / 8; > + unsigned int fence = pb->fence; > + > + if (pb->fence < pb->pos) > + fence += pb->size; > + > + return (fence - pb->pos) / 8; > } > > /* >
Reviewed-by: Dmitry Osipenko <[email protected]> Tested-by: Dmitry Osipenko <[email protected]> _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
