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bh=7hX8pcfClyecpQ+u2ryVt37NGwkCMaGiDqwps6yjoeo=; b=Sfr0C4tiFuVLb4HBBp7d1y8jknOLIxDb2tgwj8A5hyYTYMpTamG7vDRwX0d8ooqrhJWS xbzM7Q4ZpWXf3u3x03PmH9KFnCjRu8jR+H2oQIxvFkWI+4sLB61YRDkyRZ6vm4Ot77HB PsPKV6/F81y8AUQFK39e3C6jK5sJp3Theto= From: To: CC: , , , , , Peter Delevoryas Subject: [PATCH v2 1/1] hw/arm/aspeed: Initialize AST2600 UART clock selection registers Date: Mon, 6 Sep 2021 06:40:23 -0700 Message-ID: <20210906134023.3711031-2-pdel@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210906134023.3711031-1-pdel@fb.com> References: <20210906134023.3711031-1-pdel@fb.com> X-FB-Internal: Safe X-FB-Source: Intern X-Proofpoint-GUID: xY9OEadA6vcwW9URUYBwBXfs6QM8NHfe X-Proofpoint-ORIG-GUID: xY9OEadA6vcwW9URUYBwBXfs6QM8NHfe Content-Transfer-Encoding: quoted-printable X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-09-06_06:2021-09-03, 2021-09-06 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 suspectscore=0 lowpriorityscore=0 spamscore=0 phishscore=0 malwarescore=0 adultscore=0 mlxlogscore=999 impostorscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2108310000 definitions=main-2109060086 X-FB-Internal: deliver Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=67.231.153.30; envelope-from=prvs=888312a924=pdel@fb.com; helo=mx0a-00082601.pphosted.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.391, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @fb.com) X-ZM-MESSAGEID: 1630935760437100001 Content-Type: text/plain; charset="utf-8" From: Peter Delevoryas UART5 is typically used as the default debug UART on the AST2600, but UART1 is also designed to be a debug UART. All the AST2600 UART's have semi-configurable clock rates through registers in the System Control Unit (SCU), but only UART5 works out of the box with zero-initialized values. The rest of the UART's expect a few of the registers to be initialized to non-zero values, or else the clock rate calculation will yield zero or undefined (due to a divide-by-zero). For reference, the U-Boot clock rate driver here shows the calculation: https://github.com/facebook/openbmc-uboot/blob/15f7e0dc01d8/drivers/clk= /aspeed/clk_ast2600.c#L357 To summarize, UART5 allows selection from 4 rates: 24 MHz, 192 MHz, 24 / 13 MHz, and 192 / 13 MHz. The other UART's allow selecting either the "low" rate (UARTCLK) or the "high" rate (HUARTCLK). UARTCLK and HUARTCLK are configurable themselves: UARTCLK =3D UXCLK * R / (N * 2) HUARTCLK =3D HUXCLK * HR / (HN * 2) UXCLK and HUXCLK are also configurable, and depend on the APLL and/or HPLL clock rates, which also derive from complicated calculations. Long story short, there's lots of multiplication and division from configurable registers, and most of these registers are zero-initialized in QEMU, which at best is unexpected and at worst causes this clock rate driver to hang from divide-by-zero's. This can also be difficult to diagnose, because it may cause U-Boot to hang before serial console initialization completes, requiring intervention from gdb. This change just initializes all of these registers with default values from the datasheet. To test this, I used Facebook's AST2600 OpenBMC image for "fuji", with the following diff applied (because fuji uses UART1 for console output, not UART5). @@ -323,8 +323,8 @@ static void aspeed_soc_ast2600_realize(DeviceState *d= ev, Error **errp) } /* UART - attach an 8250 to the IO space as our UART5 */ - serial_mm_init(get_system_memory(), sc->memmap[ASPEED_DEV_UART5], 2, - aspeed_soc_get_irq(s, ASPEED_DEV_UART5), + serial_mm_init(get_system_memory(), sc->memmap[ASPEED_DEV_UART1], 2, + aspeed_soc_get_irq(s, ASPEED_DEV_UART1), 38400, serial_hd(0), DEVICE_LITTLE_ENDIAN); /* I2C */ Without these clock rate registers being initialized, U-Boot hangs in the clock rate driver from a divide-by-zero, because the UART1 clock rate register reads return zero, and there's no console output. After initializing them with default values, fuji boots successfully. Signed-off-by: Peter Delevoryas Reviewed-by: Joel Stanley --- hw/misc/aspeed_scu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/misc/aspeed_scu.c b/hw/misc/aspeed_scu.c index 05edebedeb..a95dca65f2 100644 --- a/hw/misc/aspeed_scu.c +++ b/hw/misc/aspeed_scu.c @@ -119,6 +119,8 @@ #define AST2600_CLK_SEL3 TO_REG(0x308) #define AST2600_CLK_SEL4 TO_REG(0x310) #define AST2600_CLK_SEL5 TO_REG(0x314) +#define AST2600_UARTCLK_PARAM TO_REG(0x338) +#define AST2600_HUARTCLK_PARAM TO_REG(0x33C) #define AST2600_HW_STRAP1 TO_REG(0x500) #define AST2600_HW_STRAP1_CLR TO_REG(0x504) #define AST2600_HW_STRAP1_PROT TO_REG(0x508) @@ -681,6 +683,8 @@ static const uint32_t ast2600_a3_resets[ASPEED_AST2600_= SCU_NR_REGS] =3D { [AST2600_CLK_SEL3] =3D 0x00000000, [AST2600_CLK_SEL4] =3D 0xF3F40000, [AST2600_CLK_SEL5] =3D 0x30000000, + [AST2600_UARTCLK_PARAM] =3D 0x00014506, + [AST2600_HUARTCLK_PARAM] =3D 0x000145C0, [AST2600_CHIP_ID0] =3D 0x1234ABCD, [AST2600_CHIP_ID1] =3D 0x88884444, }; --=20 2.30.2