From mboxrd@z Thu Jan 1 00:00:00 1970 From: guoren@kernel.org Date: Tue, 8 Aug 2023 09:29:58 -0400 Subject: [PATCH] docs/platform: thead-c9xx: Improve the documentation Message-ID: <20230808132958.1097873-1-guoren@kernel.org> List-Id: To: opensbi@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit From: Guo Ren Add detailed information about thead,reset-sample driver, and improve usage documentation. Signed-off-by: Guo Ren Signed-off-by: Guo Ren --- docs/platform/thead-c9xx.md | 87 ++++++++++++++++++++++++++++--------- 1 file changed, 67 insertions(+), 20 deletions(-) diff --git a/docs/platform/thead-c9xx.md b/docs/platform/thead-c9xx.md index 8bb9e91f1a9b..fe05fc5bb85a 100644 --- a/docs/platform/thead-c9xx.md +++ b/docs/platform/thead-c9xx.md @@ -1,8 +1,8 @@ -T-HEAD C9xx Series Processors -============================= +T-HEAD Processors +================= -The **C9xx** series processors are high-performance RISC-V architecture -multi-core processors with AI vector acceleration engine. +T-HEAD provides high-performance RISC-V architecture multi-core +processors with AI vector acceleration engine. For more details, refer [T-HEAD.CN](https://www.t-head.cn/) @@ -12,15 +12,75 @@ To build the platform-specific library and firmware images, provide the Platform Options ---------------- -The *T-HEAD C9xx* does not have any platform-specific compile options +The *T-HEAD CPU* does not have any platform-specific compile options because it uses generic platform. ``` CROSS_COMPILE=riscv64-linux-gnu- PLATFORM=generic /usr/bin/make ``` -The *T-HEAD C9xx* DTB provided to OpenSBI generic firmwares will usually have -"riscv,clint0", "riscv,plic0", "thead,reset-sample" compatible strings. +The *T-HEAD CPU* DTB provided to OpenSBI generic firmwares will usually have +"thead,reset-sample" compatible strings. The "thead,reset-sample" is a T-HEAD +custom driver for the SMP system bootup; the single-core system doesn't need +it. + +T-HEAD Fdt Reset Driver Introduction +------------------------------------ + +Every T-HEAD CPU provides a reset control signal and reset address signals. + - Reset address signal determines CPU where to start up. + - Reset control signal releases CPU from reset state and begins to execute + at reset address. + +Many vendors would gather these signals into SoC control registers. These +register designs are similar but with different base addresses and bits +definitions. We only provide standard opensbi, Linux binaries, and jtag gdbinit +script to simplify Linux booting at the FPGA stage. The fdt reset driver helps +users bring up their SMP system quickly with the below settings: + + - entry-reg: + The base address to store reset address value + + - entry-cnt: + The numbers of entry-reg, all of them set the same reset address + + - control-reg: + The base address to reset the controller + + - control-val: + Write which bits of control-reg for booting + + - csr-copy: + This array determines which csrs to copy from primary hart to the + secondary harts, which are set in sequence from left to right. The + secondary harts should keep the same setting as the primary hart. + These settings are also the first part of the bootup instructions + for secondary harts. + + - using-csr-reset: + A legacy reset controller for the SMP system, but abandoned in the + latest T-HEAD processors. + +Here is the dts example: +``` + reset: reset-sample { + compatible = "thead,reset-sample"; + entry-reg = <0xff 0xff019050>; + entry-cnt = <4>; + control-reg = <0xff 0xff015004>; + control-val = <0x1c>; + csr-copy = <0x7f3 0x7c0 0x7c1 0x7c2 0x7c3 0x7c5 0x7cc>; + }; +``` + +Legacy dts example (Abandoned): +``` + reset: reset-sample { + compatible = "thead,reset-sample"; + using-csr-reset; + csr-copy = <0x7f3 0x7c0 0x7c1 0x7c2 0x7c3 0x7c5 0x7cc>; + }; +``` DTS Example1: (Single core, eg: Allwinner D1 - c906) ---------------------------------------------------- @@ -181,16 +241,3 @@ DTS Example2: (Multi cores with soc reset-regs) }; } ``` - -DTS Example2: (Multi cores with old reset csrs) ------------------------------------------------ -``` - reset: reset-sample { - compatible = "thead,reset-sample"; - using-csr-reset; - csr-copy = <0x7c0 0x7c1 0x7c2 0x7c3 0x7c5 0x7cc - 0x3b0 0x3b1 0x3b2 0x3b3 - 0x3b4 0x3b5 0x3b6 0x3b7 - 0x3a0>; - }; -``` -- 2.36.1