From 7652b2f12c0acdc22d29deb4f786364c80c8528f Mon Sep 17 00:00:00 2001 From: Giacomo Travaglini Date: Mon, 24 Jun 2019 16:41:26 +0100 Subject: [PATCH] dev-arm: Fix SMMUv3 CMDQ wrapping SMMU circular queues have a wrap bit which is used in order to distinguish between an empty queue and a full queue. According to SMMUv3 spec: Each index has a wrap flag, represented by the next higher bit adjacent to the index value contained in PROD and CONS. This bit must toggle each time the index wraps off the high end and back onto the low end of the buffer. It is the responsibility of the owner of each index, producer or consumer, to toggle this bit when the owner updates the index after wrapping. It is intended that software reads the register, increments or wraps the index (toggling wrap when required) and writes back both wrap and index fields at the same time. Change-Id: Idfeb397141f3627c2878caaeaa2625fadf671d2a Signed-off-by: Giacomo Travaglini Reviewed-by: Michiel Van Tol Reviewed-by: Adrian Herrera Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19311 Tested-by: kokoro Reviewed-by: Ciro Santilli Maintainer: Andreas Sandberg --- src/dev/arm/smmu_v3_cmdexec.cc | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/src/dev/arm/smmu_v3_cmdexec.cc b/src/dev/arm/smmu_v3_cmdexec.cc index 48896bf96..5b9dc6e4a 100644 --- a/src/dev/arm/smmu_v3_cmdexec.cc +++ b/src/dev/arm/smmu_v3_cmdexec.cc @@ -56,20 +56,28 @@ SMMUCommandExecProcess::main(Yield &yield) busy = true; while (true) { - int sizeMask = mask(smmu.regs.cmdq_base & Q_BASE_SIZE_MASK); + // Masking depending on CMDQ_BASE.LOG2SIZE (log(number of + // queue entries)). Example: a value of 0b101 (32 entries) + // generates a 0b11111 mask. + int size_mask = mask( + smmu.regs.cmdq_base & Q_BASE_SIZE_MASK); - if ((smmu.regs.cmdq_cons & sizeMask) == - (smmu.regs.cmdq_prod & sizeMask)) + // In this case the wrap bit is considered (+1) + int size_mask_wrap = mask( + (smmu.regs.cmdq_base & Q_BASE_SIZE_MASK) + 1); + + if ((smmu.regs.cmdq_cons & size_mask_wrap) == + (smmu.regs.cmdq_prod & size_mask_wrap)) break; // command queue empty - Addr cmdAddr = + Addr cmd_addr = (smmu.regs.cmdq_base & Q_BASE_ADDR_MASK) + - (smmu.regs.cmdq_cons & sizeMask) * sizeof(SMMUCommand); + (smmu.regs.cmdq_cons & size_mask) * sizeof(SMMUCommand); // This deliberately resets the error field in cmdq_cons! - smmu.regs.cmdq_cons = (smmu.regs.cmdq_cons + 1) & sizeMask; + smmu.regs.cmdq_cons = (smmu.regs.cmdq_cons + 1) & size_mask_wrap; - doRead(yield, cmdAddr, &cmd, sizeof(SMMUCommand)); + doRead(yield, cmd_addr, &cmd, sizeof(SMMUCommand)); smmu.processCommand(cmd); } -- 2.30.2