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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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4c7085a5d5
Add a shadow pointer to track the current command being written into the ring. Don't commit it as 'cur' until the command is submitted. Because 'cur' is used to construct the software copy of the wptr this ensures that somebody peeking in on the ring doesn't assume that a command is inflight while it is being written. This isn't a huge deal with a single ring (though technically the hangcheck could assume the system is prematurely busy when it isn't) but it will be rather important for preemption where the decision to preempt is based on a non-empty ringbuffer. Without a shadow an aggressive preemption scheme could assume that the ringbuffer is non empty and switch to it before the CPU is done writing the command and boom. Even though preemption won't be supported for all targets because of the way the code is organized it is simpler to make this generic for all targets. The extra load for non-preemption targets should be minimal. Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org> Signed-off-by: Rob Clark <robdclark@gmail.com>
64 lines
1.7 KiB
C
64 lines
1.7 KiB
C
/*
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* Copyright (C) 2013 Red Hat
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* Author: Rob Clark <robdclark@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __MSM_RINGBUFFER_H__
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#define __MSM_RINGBUFFER_H__
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#include "msm_drv.h"
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#define rbmemptr(ring, member) \
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((ring)->memptrs_iova + offsetof(struct msm_rbmemptrs, member))
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struct msm_rbmemptrs {
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volatile uint32_t rptr;
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volatile uint32_t fence;
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};
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struct msm_ringbuffer {
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struct msm_gpu *gpu;
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int id;
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struct drm_gem_object *bo;
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uint32_t *start, *end, *cur, *next;
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struct list_head submits;
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uint64_t iova;
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uint32_t seqno;
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uint32_t hangcheck_fence;
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struct msm_rbmemptrs *memptrs;
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uint64_t memptrs_iova;
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struct msm_fence_context *fctx;
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};
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struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
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void *memptrs, uint64_t memptrs_iova);
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void msm_ringbuffer_destroy(struct msm_ringbuffer *ring);
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/* ringbuffer helpers (the parts that are same for a3xx/a2xx/z180..) */
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static inline void
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OUT_RING(struct msm_ringbuffer *ring, uint32_t data)
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{
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/*
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* ring->next points to the current command being written - it won't be
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* committed as ring->cur until the flush
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*/
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if (ring->next == ring->end)
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ring->next = ring->start;
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*(ring->next++) = data;
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}
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#endif /* __MSM_RINGBUFFER_H__ */
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