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Thu, 16 Nov 2023 14:17:11 +0000 Message-ID: <9282e81c-51a6-46be-bcfa-dfec2f04a817@amd.com> Date: Thu, 16 Nov 2023 15:17:05 +0100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH-for-8.2] hw/net/can/xlnx-zynqmp: Avoid underflow while popping TX FIFO Content-Language: en-US To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Cc: Pavel Pisa , Jason Wang , Vikram Garhwal , Anton Kochkov , Qiang Liu References: <20231115151711.89170-1-philmd@linaro.org> From: Francisco Iglesias In-Reply-To: <20231115151711.89170-1-philmd@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: PA7P264CA0323.FRAP264.PROD.OUTLOOK.COM (2603:10a6:102:395::11) To SJ2PR12MB8739.namprd12.prod.outlook.com (2603:10b6:a03:549::10) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR12MB8739:EE_|IA1PR12MB8190:EE_ X-MS-Office365-Filtering-Correlation-Id: 2a7ac252-7da2-48c5-cfc8-08dbe6aeb92d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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envelope-from=francisco.iglesias@amd.com; helo=NAM10-DM6-obe.outbound.protection.outlook.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.117, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi Philippe, good catch! On 2023-11-15 16:17, Philippe Mathieu-Daudé wrote: > Per https://docs.xilinx.com/r/en-US/ug1085-zynq-ultrascale-trm/Message-Format > > Message Format > > The same message format is used for RXFIFO, TXFIFO, and TXHPB. > Each message includes four words (16 bytes). Software must read > and write all four words regardless of the actual number of data > bytes and valid fields in the message. > > There is no mention in this reference manual about what the > hardware does when not all four words are written. To fix the > reported underflow behavior when DATA2 register is written, > I choose to fill the data with the previous content of the > ID / DLC / DATA1 registers, which is how I expect hardware > would do. > > Note there is no hardware flag raised under such condition. > > Reported-by: Qiang Liu > Fixes: 98e5d7a2b7 ("hw/net/can: Introduce Xilinx ZynqMP CAN controller") > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1425 > Signed-off-by: Philippe Mathieu-Daudé > --- > Tested with the CAN tests from 'make check-qtest-aarch64' > --- > hw/net/can/xlnx-zynqmp-can.c | 49 +++++++++++++++++++++++++++++++++--- > 1 file changed, 46 insertions(+), 3 deletions(-) > > diff --git a/hw/net/can/xlnx-zynqmp-can.c b/hw/net/can/xlnx-zynqmp-can.c > index e93e6c5e19..58938b574e 100644 > --- a/hw/net/can/xlnx-zynqmp-can.c > +++ b/hw/net/can/xlnx-zynqmp-can.c > @@ -434,6 +434,51 @@ static bool tx_ready_check(XlnxZynqMPCANState *s) > return true; > } > > +static void read_tx_frame(XlnxZynqMPCANState *s, Fifo32 *fifo, uint32_t *data) > +{ > + unsigned used = fifo32_num_used(fifo); For the case when there are multiple frames in the fifo we need to swap above to: unsigned used = fifo32_num_used(fifo) > CAN_FRAME_SIZE ? 0 : fifo32_num_used(fifo); With above minor modification: Reviewed-by: Francisco Iglesias Best regards, Francisco > + bool is_txhpb = fifo == &s->txhpb_fifo; > + > + assert(used > 0); > + used %= CAN_FRAME_SIZE; > + > + /* > + * Frame Message Format > + * > + * Each frame includes four words (16 bytes). Software must read and write > + * all four words regardless of the actual number of data bytes and valid > + * fields in the message. > + * If software misbehave (not writting all four words), we use the previous > + * registers content to initialize each missing word. > + */ > + if (used > 0) { > + /* ID, DLC, DATA1 missing */ > + data[0] = s->regs[is_txhpb ? R_TXHPB_ID : R_TXFIFO_ID]; > + } else { > + data[0] = fifo32_pop(fifo); > + } > + if (used == 1 || used == 2) { > + /* DLC, DATA1 missing */ > + data[1] = s->regs[is_txhpb ? R_TXHPB_DLC : R_TXFIFO_DLC]; > + } else { > + data[1] = fifo32_pop(fifo); > + } > + if (used == 1) { > + /* DATA1 missing */ > + data[2] = s->regs[is_txhpb ? R_TXHPB_DATA1 : R_TXFIFO_DATA1]; > + } else { > + data[2] = fifo32_pop(fifo); > + } > + /* DATA2 triggered the transfer thus is always available */ > + data[3] = fifo32_pop(fifo); > + > + if (used) { > + qemu_log_mask(LOG_GUEST_ERROR, > + "%s: Incomplete CAN frame (only %u/%u slots used)\n", > + TYPE_XLNX_ZYNQMP_CAN, used, CAN_FRAME_SIZE); > + } > +} > + > static void transfer_fifo(XlnxZynqMPCANState *s, Fifo32 *fifo) > { > qemu_can_frame frame; > @@ -451,9 +496,7 @@ static void transfer_fifo(XlnxZynqMPCANState *s, Fifo32 *fifo) > } > > while (!fifo32_is_empty(fifo)) { > - for (i = 0; i < CAN_FRAME_SIZE; i++) { > - data[i] = fifo32_pop(fifo); > - } > + read_tx_frame(s, fifo, data); > > if (ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, LBACK)) { > /*