| Message ID | 20240414-arm-psci-system_reset2-vendor-reboots-v2-0-da9a055a648f@quicinc.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Implement vendor resets for PSCI SYSTEM_RESET2 | expand |
On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > reset types which could be mapped to the reboot argument. > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > to chipset. That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as expected ? Does it mean it is not conformant to the specification ? > Generally, there is a PMIC register that gets written to > decide the reboot type. There is also sometimes a cookie that can be > written to indicate that the bootloader should behave differently than a > regular boot. These knobs evolve over product generations and require > more drivers. Qualcomm firmwares are beginning to expose vendor > SYSTEM_RESET2 types to simplify driver requirements from Linux. > Why can't this be fully userspace driven ? What is the need to keep the cookie in the DT ?
On 4/16/24 02:35, Sudeep Holla wrote: > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: >> The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional >> reset types which could be mapped to the reboot argument. >> >> Setting up reboot on Qualcomm devices can be inconsistent from chipset >> to chipset. > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > expected ? Does it mean it is not conformant to the specification ? > >> Generally, there is a PMIC register that gets written to >> decide the reboot type. There is also sometimes a cookie that can be >> written to indicate that the bootloader should behave differently than a >> regular boot. These knobs evolve over product generations and require >> more drivers. Qualcomm firmwares are beginning to expose vendor >> SYSTEM_RESET2 types to simplify driver requirements from Linux. >> > > Why can't this be fully userspace driven ? What is the need to keep the > cookie in the DT ? > > Using the second example in the Device Tree: mode-bootloader = <1 2>; are you suggesting that within psci_vendor_sys_reset2() we would look at the data argument and assume that we have something like this in memory: const char *cmd = data; cmd[] = "bootloader 2" where "bootloader" is the reboot command, and "2" is the cookie? From an util-linux, busybox, toybox, etc. we would have to concatenate those arguments with a space, but I suppose that would be doable. For the use cases that I am after we did not have a need for the cookie, so I admit I did not think too much about it.
On Tue, Apr 16, 2024 at 10:35:22AM +0100, Sudeep Holla wrote: > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > reset types which could be mapped to the reboot argument. > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > to chipset. > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > expected ? Does it mean it is not conformant to the specification ? > I was motivating the reason for using SYSTEM_RESET2. How to set the PMIC register and IMEM cookie can change between chipsets. Using SYSTEM_RESET2 alows us to abstract how to perform the reset. > > Generally, there is a PMIC register that gets written to > > decide the reboot type. There is also sometimes a cookie that can be > > written to indicate that the bootloader should behave differently than a > > regular boot. These knobs evolve over product generations and require > > more drivers. Qualcomm firmwares are beginning to expose vendor > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > Why can't this be fully userspace driven ? What is the need to keep the > cookie in the DT ? As Dmitry pointed out, this information isn't discoverable. I suppose we could technically use bootconfig or kernel command-line to convey the map although I think devicetree is the right spot for this mapping. - Other vendor-specific bits for PSCI are described in the devicetree. One example is the suspend param (e.g. the StateID) for cpu idle states. - Describing firmware bits in the DT isn't unprecedented, and putting this information outside the DT means that other OSes (besides Linux) need their own way to convey this information. - PSCI would be the odd one out that reboot mode map is not described in DT. Other reboot-mode drivers specify the mapping in the DT. Userspace that runs with firmware that support vendor reset2 need to make sure they can configure the mapping early enough. Thanks, Elliot
On 4/17/24 14:54, Elliot Berman wrote: > On Tue, Apr 16, 2024 at 10:35:22AM +0100, Sudeep Holla wrote: >> On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: >>> The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional >>> reset types which could be mapped to the reboot argument. >>> >>> Setting up reboot on Qualcomm devices can be inconsistent from chipset >>> to chipset. >> >> That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as >> expected ? Does it mean it is not conformant to the specification ? >> > > I was motivating the reason for using SYSTEM_RESET2. How to set the PMIC > register and IMEM cookie can change between chipsets. Using > SYSTEM_RESET2 alows us to abstract how to perform the reset. > >>> Generally, there is a PMIC register that gets written to >>> decide the reboot type. There is also sometimes a cookie that can be >>> written to indicate that the bootloader should behave differently than a >>> regular boot. These knobs evolve over product generations and require >>> more drivers. Qualcomm firmwares are beginning to expose vendor >>> SYSTEM_RESET2 types to simplify driver requirements from Linux. >>> >> >> Why can't this be fully userspace driven ? What is the need to keep the >> cookie in the DT ? > > As Dmitry pointed out, this information isn't discoverable. I suppose > we could technically use bootconfig or kernel command-line to convey the > map although I think devicetree is the right spot for this mapping. > > - Other vendor-specific bits for PSCI are described in the devicetree. > One example is the suspend param (e.g. the StateID) for cpu idle > states. > - Describing firmware bits in the DT isn't unprecedented, and putting > this information outside the DT means that other OSes (besides Linux) > need their own way to convey this information. > - PSCI would be the odd one out that reboot mode map is not described in > DT. Other reboot-mode drivers specify the mapping in the DT. Userspace > that runs with firmware that support vendor reset2 need to make sure > they can configure the mapping early enough. FWIW, I read Sudeep's response as being specifically inquiring about the 'cookie' parameter, do you see a need for that to be in described in the DT or could that just be an user-space parameter that is conveyed through the reboot system call?
On Wed, Apr 17, 2024 at 03:01:00PM -0700, Florian Fainelli wrote: > On 4/17/24 14:54, Elliot Berman wrote: > > On Tue, Apr 16, 2024 at 10:35:22AM +0100, Sudeep Holla wrote: > > > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > > > reset types which could be mapped to the reboot argument. > > > > > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > > > to chipset. > > > > > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > > > expected ? Does it mean it is not conformant to the specification ? > > > > > > > I was motivating the reason for using SYSTEM_RESET2. How to set the PMIC > > register and IMEM cookie can change between chipsets. Using > > SYSTEM_RESET2 alows us to abstract how to perform the reset. > > > > > > Generally, there is a PMIC register that gets written to > > > > decide the reboot type. There is also sometimes a cookie that can be > > > > written to indicate that the bootloader should behave differently than a > > > > regular boot. These knobs evolve over product generations and require > > > > more drivers. Qualcomm firmwares are beginning to expose vendor > > > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > > > > > > > Why can't this be fully userspace driven ? What is the need to keep the > > > cookie in the DT ? > > > > As Dmitry pointed out, this information isn't discoverable. I suppose > > we could technically use bootconfig or kernel command-line to convey the > > map although I think devicetree is the right spot for this mapping. > > > > - Other vendor-specific bits for PSCI are described in the devicetree. > > One example is the suspend param (e.g. the StateID) for cpu idle > > states. > > - Describing firmware bits in the DT isn't unprecedented, and putting > > this information outside the DT means that other OSes (besides Linux) > > need their own way to convey this information. > > - PSCI would be the odd one out that reboot mode map is not described in > > DT. Other reboot-mode drivers specify the mapping in the DT. Userspace > > that runs with firmware that support vendor reset2 need to make sure > > they can configure the mapping early enough. > > FWIW, I read Sudeep's response as being specifically inquiring about the > 'cookie' parameter, do you see a need for that to be in described in the DT > or could that just be an user-space parameter that is conveyed through the > reboot system call? Ah, I had thought the ask was for the reboot type as well as the cookie. We don't do this for hardware-based reboot mode cookies and I didn't see why we should ask userspace to do something different for PSCI. It seems to me that SYSTEM_RESET2 fits nicely with the existing design for reboot-mode bindings.
On Wed, Apr 17, 2024 at 02:54:41PM -0700, Elliot Berman wrote: > On Tue, Apr 16, 2024 at 10:35:22AM +0100, Sudeep Holla wrote: > > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > > reset types which could be mapped to the reboot argument. > > > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > > to chipset. > > > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > > expected ? Does it mean it is not conformant to the specification ? > > > > I was motivating the reason for using SYSTEM_RESET2. How to set the PMIC > register and IMEM cookie can change between chipsets. Using > SYSTEM_RESET2 alows us to abstract how to perform the reset. Fair enough. But I assume you are not providing the details of PMIC register or IMEM cookie via DT. Anyways you did confirm if PSCI SYSTEM_RESET works as expected or not. That is default and must work. > > > Generally, there is a PMIC register that gets written to > > > decide the reboot type. There is also sometimes a cookie that can be > > > written to indicate that the bootloader should behave differently than a > > > regular boot. These knobs evolve over product generations and require > > > more drivers. Qualcomm firmwares are beginning to expose vendor > > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > > > > Why can't this be fully userspace driven ? What is the need to keep the > > cookie in the DT ? > > As Dmitry pointed out, this information isn't discoverable. I suppose > we could technically use bootconfig or kernel command-line to convey the > map although I think devicetree is the right spot for this mapping. > Yes and as usual DT has become dumping ground for firmware that don't make things discoverable. Make crap that Qcom puts in the DT are firmware related and can be make discoverable. Anyways it is sad that no efforts to make it so are done as DT is always there to provide shortcuts. > - Other vendor-specific bits for PSCI are described in the devicetree. > One example is the suspend param (e.g. the StateID) for cpu idle > states. You are right, but that is the only example I can see and it was done in very early days of PSCI. It shouldn't be example if there are better ways. > - Describing firmware bits in the DT isn't unprecedented, and putting > this information outside the DT means that other OSes (besides Linux) > need their own way to convey this information. Correct but it can be Qcom specific firmware interface. There are so many already. This splitting information between firmware and DT works well for vertically integrated things which probably is the case with most of Qcom SoCs but it is prone to issues if DT and firmware mismatch. Firmware discovery eliminates such issues. > - PSCI would be the odd one out that reboot mode map is not described in > DT. Other reboot-mode drivers specify the mapping in the DT. Userspace > that runs with firmware that support vendor reset2 need to make sure > they can configure the mapping early enough. > Well I am not saying not to this yet, just exploring and getting more info so that whatever is done here can be reused on all PSCI based systems. -- Regards, Sudeep
On Wed, Apr 17, 2024 at 10:50:07AM -0700, Florian Fainelli wrote: > On 4/16/24 02:35, Sudeep Holla wrote: > > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > > reset types which could be mapped to the reboot argument. > > > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > > to chipset. > > > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > > expected ? Does it mean it is not conformant to the specification ? > > > > > Generally, there is a PMIC register that gets written to > > > decide the reboot type. There is also sometimes a cookie that can be > > > written to indicate that the bootloader should behave differently than a > > > regular boot. These knobs evolve over product generations and require > > > more drivers. Qualcomm firmwares are beginning to expose vendor > > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > > > > Why can't this be fully userspace driven ? What is the need to keep the > > cookie in the DT ? > > > > > > Using the second example in the Device Tree: > > mode-bootloader = <1 2>; > > are you suggesting that within psci_vendor_sys_reset2() we would look at the > data argument and assume that we have something like this in memory: > > const char *cmd = data; > > cmd[] = "bootloader 2" > > where "bootloader" is the reboot command, and "2" is the cookie? From an > util-linux, busybox, toybox, etc. we would have to concatenate those > arguments with a space, but I suppose that would be doable. > Yes that was my thought when I wrote the email. But since I have looked at existing bindings and support in the kernel in little more detail I would say. So I am not sure what would be the better choice for PSCI SYSTEM_RESET2 especially when there is some ground support to build. So I am open for alternatives including this approach. -- Regards, Sudeep
On Fri, Apr 19, 2024 at 09:53:45AM +0100, Sudeep Holla wrote: > On Wed, Apr 17, 2024 at 02:54:41PM -0700, Elliot Berman wrote: > > On Tue, Apr 16, 2024 at 10:35:22AM +0100, Sudeep Holla wrote: > > > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > > > reset types which could be mapped to the reboot argument. > > > > > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > > > to chipset. > > > > > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > > > expected ? Does it mean it is not conformant to the specification ? > > > > > > > I was motivating the reason for using SYSTEM_RESET2. How to set the PMIC > > register and IMEM cookie can change between chipsets. Using > > SYSTEM_RESET2 alows us to abstract how to perform the reset. > > Fair enough. But I assume you are not providing the details of PMIC register > or IMEM cookie via DT. Kernel doesn't need this info. > > Anyways you did confirm if PSCI SYSTEM_RESET works as expected or not. That > is default and must work. > Yes, SYSTEM_RESET works on Quacomm firmware. The bindings disallow trying to override the default reboot. (reboot command = NULL or "") The PSCI parsing of the DT also doesn't have any of the special handling to deal with "mode-normal". > > > > Generally, there is a PMIC register that gets written to > > > > decide the reboot type. There is also sometimes a cookie that can be > > > > written to indicate that the bootloader should behave differently than a > > > > regular boot. These knobs evolve over product generations and require > > > > more drivers. Qualcomm firmwares are beginning to expose vendor > > > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > > > > > > > Why can't this be fully userspace driven ? What is the need to keep the > > > cookie in the DT ? > > > > As Dmitry pointed out, this information isn't discoverable. I suppose > > we could technically use bootconfig or kernel command-line to convey the > > map although I think devicetree is the right spot for this mapping. > > > > Yes and as usual DT has become dumping ground for firmware that don't > make things discoverable. Make crap that Qcom puts in the DT are firmware > related and can be make discoverable. Anyways it is sad that no efforts > to make it so are done as DT is always there to provide shortcuts. > > > - Other vendor-specific bits for PSCI are described in the devicetree. > > One example is the suspend param (e.g. the StateID) for cpu idle > > states. > > You are right, but that is the only example I can see and it was done > in very early days of PSCI. It shouldn't be example if there are better > ways. > > > - Describing firmware bits in the DT isn't unprecedented, and putting > > this information outside the DT means that other OSes (besides Linux) > > need their own way to convey this information. > > Correct but it can be Qcom specific firmware interface. There are so many > already. This splitting information between firmware and DT works well > for vertically integrated things which probably is the case with most of > Qcom SoCs but it is prone to issues if DT and firmware mismatch. Firmware > discovery eliminates such issues. > I worry about designing interfaces both in Qualcomm firmware and in the PSCI driver which doesn't really suit handling the discovery. We can implement the dynamic discovery mechanims once there is a board which needs it. Thanks, Elliot
On Fri, Apr 19, 2024 at 01:38:47PM +0100, Sudeep Holla wrote: > On Wed, Apr 17, 2024 at 10:50:07AM -0700, Florian Fainelli wrote: > > On 4/16/24 02:35, Sudeep Holla wrote: > > > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > > > reset types which could be mapped to the reboot argument. > > > > > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > > > to chipset. > > > > > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > > > expected ? Does it mean it is not conformant to the specification ? > > > > > > > Generally, there is a PMIC register that gets written to > > > > decide the reboot type. There is also sometimes a cookie that can be > > > > written to indicate that the bootloader should behave differently than a > > > > regular boot. These knobs evolve over product generations and require > > > > more drivers. Qualcomm firmwares are beginning to expose vendor > > > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > > > > > > > Why can't this be fully userspace driven ? What is the need to keep the > > > cookie in the DT ? > > > > > > > > > > Using the second example in the Device Tree: > > > > mode-bootloader = <1 2>; > > > > are you suggesting that within psci_vendor_sys_reset2() we would look at the > > data argument and assume that we have something like this in memory: > > > > const char *cmd = data; > > > > cmd[] = "bootloader 2" > > > > where "bootloader" is the reboot command, and "2" is the cookie? From an > > util-linux, busybox, toybox, etc. we would have to concatenate those > > arguments with a space, but I suppose that would be doable. > > > > Yes that was my thought when I wrote the email. But since I have looked at > existing bindings and support in the kernel in little more detail I would say. > So I am not sure what would be the better choice for PSCI SYSTEM_RESET2 > especially when there is some ground support to build. > > So I am open for alternatives including this approach. If we can't go with the DT approach, my preference would be to go with a bootconfig and sysfs for controlling the mappings, although I don't think userspace need/should control the mappings of cmd -> cookies. I wanted to check if you are okay with proceeding with the reboot-mode DT bindings approach unless we have some other better standard? If yes, do you have any preference based on Konrad's comment [1]? I can send out v3 with the couple comments from Dmitry and Krzysztof's addressed. Thanks, Elliot [1]: https://lore.kernel.org/all/20240419123847.ica22nft3sejqnm7@bogus/
The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional reset types which could be mapped to the reboot argument. Setting up reboot on Qualcomm devices can be inconsistent from chipset to chipset. Generally, there is a PMIC register that gets written to decide the reboot type. There is also sometimes a cookie that can be written to indicate that the bootloader should behave differently than a regular boot. These knobs evolve over product generations and require more drivers. Qualcomm firmwares are beginning to expose vendor SYSTEM_RESET2 types to simplify driver requirements from Linux. Add support in PSCI to statically wire reboot mode commands from userspace to a vendor reset and cookie value using the device tree. The DT bindings are similar to reboot mode framework except that 2 integers are accepted (the type and cookie). Also, reboot mode framework is intended to program, but not reboot, the host. PSCI SYSTEM_RESET2 does both. I've not added support for reading ACPI tables since I don't have any device which provides them + firmware that supports vendor SYSTEM_RESET2 types. Previous discussions around SYSTEM_RESET2: - https://lore.kernel.org/lkml/20230724223057.1208122-2-quic_eberman@quicinc.com/T/ - https://lore.kernel.org/all/4a679542-b48d-7e11-f33a-63535a5c68cb@quicinc.com/ Signed-off-by: Elliot Berman <quic_eberman@quicinc.com> --- Changes in v2: - Fixes to schema as suggested by Rob and Krzysztof - Add qcm6490 idp as first Qualcomm device to support - Link to v1: https://lore.kernel.org/r/20231117-arm-psci-system_reset2-vendor-reboots-v1-0-03c4612153e2@quicinc.com Changes in v1: - Reference reboot-mode bindings as suggeted by Rob. - Link to RFC: https://lore.kernel.org/r/20231030-arm-psci-system_reset2-vendor-reboots-v1-0-dcdd63352ad1@quicinc.com --- Elliot Berman (4): dt-bindings: power: reset: Convert mode-.* properties to array dt-bindings: arm: Document reboot mode magic firmware: psci: Read and use vendor reset types arm64: dts: qcom: Add PSCI SYSTEM_RESET2 types for qcm6490-idp Documentation/devicetree/bindings/arm/psci.yaml | 38 ++++++++- .../bindings/power/reset/nvmem-reboot-mode.yaml | 4 + .../devicetree/bindings/power/reset/qcom,pon.yaml | 4 + .../bindings/power/reset/reboot-mode.yaml | 12 ++- .../bindings/power/reset/syscon-reboot-mode.yaml | 4 + arch/arm64/boot/dts/qcom/qcm6490-idp.dts | 5 ++ drivers/firmware/psci/psci.c | 90 ++++++++++++++++++++++ 7 files changed, 153 insertions(+), 4 deletions(-) --- base-commit: b5d2afe8745bf3eef5a59a13313798d24f2af983 change-id: 20231016-arm-psci-system_reset2-vendor-reboots-cc3ad456c070 Best regards,