From 6325c4871e913a2be50432975bf3596b7d9a9a0b Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 10 Apr 2020 09:35:35 +0100 Subject: [PATCH] agp/intel: Reinforce the barrier after GTT updates commit f30d3ced9fafa03e4855508929b5b6334907f45e upstream. After changing the timing between GTT updates and execution on the GPU, we started seeing sporadic failures on Ironlake. These were narrowed down to being an insufficiently strong enough barrier/delay after updating the GTT and scheduling execution on the GPU. By forcing the uncached read, and adding the missing barrier for the singular insert_page (relocation paths), the sporadic failures go away. Fixes: 983d308cb8f6 ("agp/intel: Serialise after GTT updates") Fixes: 3497971a71d8 ("agp/intel: Flush chipset writes after updating a single PTE") Signed-off-by: Chris Wilson Acked-by: Andi Shyti Cc: stable@vger.kernel.org # v4.0+ Link: https://patchwork.freedesktop.org/patch/msgid/20200410083535.25464-1-chris@chris-wilson.co.uk Signed-off-by: Greg Kroah-Hartman --- drivers/char/agp/intel-gtt.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c index 66a62d17a3f51..3d42fc4290bcf 100644 --- a/drivers/char/agp/intel-gtt.c +++ b/drivers/char/agp/intel-gtt.c @@ -846,6 +846,7 @@ void intel_gtt_insert_page(dma_addr_t addr, unsigned int flags) { intel_private.driver->write_entry(addr, pg, flags); + readl(intel_private.gtt + pg); if (intel_private.driver->chipset_flush) intel_private.driver->chipset_flush(); } @@ -871,7 +872,7 @@ void intel_gtt_insert_sg_entries(struct sg_table *st, j++; } } - wmb(); + readl(intel_private.gtt + j - 1); if (intel_private.driver->chipset_flush) intel_private.driver->chipset_flush(); } @@ -1105,6 +1106,7 @@ static void i9xx_cleanup(void) static void i9xx_chipset_flush(void) { + wmb(); if (intel_private.i9xx_flush_page) writel(1, intel_private.i9xx_flush_page); } -- 2.47.2