solving device tree issues part 3
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Solving Device Tree Issues - part 3 Using devicetree is painful. - PowerPoint PPT Presentation

Nov 20, 2023 •681 likes •2.09k views

Solving Device Tree Issues - part 3 Using devicetree is painful. The framework does not help to develop correct system descriptions (device tree source) and drivers. Errors are often not visible or are hard to understand. But tools and

  1. Enable Property Access Messages - Select CONFIG_OF_DEBUG_PROP - Ensure the printk buffer is large enough (CONFIG_LOG_BUF_SHIFT) - Add 'debug' to kernel command line - Rebuild kernel - Boot - Choose one of: - capture boot console output - capture output of 'dmesg' after booting

  2. Boot Console - OF_FND output Linux version 4.8.0-rc7-dirty ... ... OF: fdt:OF_FND 1 / NULL 0 OF: fdt: -> unflatten_device_tree() ... OF: OF_FND 0 / name 1 ... OF: OF_FND 0 /smd/rpm/rpm_requests/pm8941-regulators/5vs2 name 5 OF: OF_FND -22 /smd/rpm/rpm_requests/pm8941-regulators/5vs2 device_type 0 OF: fdt: <- unflatten_device_tree() OF: fdt:OF_FND 2 / NULL 0 OF: OF_FND 0 /chosen stdout-path 17 OF: adding DT alias:serial0: stem=serial id=0 node=/soc/serial@f991e000 OF: adding DT alias:usid0: stem=usid id=0 node=/soc/spmi@fc4cf000/pm8941@0 OF: adding DT alias:usid4: stem=usid id=4 node=/soc/spmi@fc4cf000/pm8841@4 OF: OF_FND 0 /cpus/cpu@0 reg 4 OF: OF_FND 0 /cpus/cpu@0 enable-method 17 OF: OF_FND 0 /cpus/cpu@1 reg 4 OF: OF_FND 0 /cpus/cpu@2 reg 4 OF: OF_FND 0 /cpus/cpu@3 reg 4 ...

  3. Boot Console - ignore unflatten Linux version 4.8.0-rc7-dirty ... ... OF: fdt:OF_FND 1 / NULL 0 <----- '1' is magic value 'OF_FND_IGNORE_BEGIN OF: fdt: -> unflatten_device_tree() ... OF: OF_FND 0 / name 1 ... OF: OF_FND 0 /smd/rpm/rpm_requests/pm8941-regulators/5vs2 name 5 OF: OF_FND -22 /smd/rpm/rpm_requests/pm8941-regulators/5vs2 device_type 0 OF: fdt: <- unflatten_device_tree() OF: fdt:OF_FND 2 / NULL 0 <----- '2' is magic value 'OF_FND_IGNORE_END Properties are accessed during the unflatten phase. These are not useful accesses for debugging purposes - they are not driver or framework accesses.

  4. Boot Console - useful output ... OF: fdt: <- unflatten_device_tree() OF: fdt:OF_FND 2 / NULL 0 <----- '2' is magic value 'OF_FND_IGNORE_END OF: OF_FND 0 /chosen stdout-path 17 OF: adding DT alias:serial0: stem=serial id=0 node=/soc/serial@f991e000 OF: adding DT alias:usid0: stem=usid id=0 node=/soc/spmi@fc4cf000/pm8941@0 OF: adding DT alias:usid4: stem=usid id=4 node=/soc/spmi@fc4cf000/pm8841@4 OF: OF_FND 0 /cpus/cpu@0 reg 4 OF: OF_FND 0 /cpus/cpu@0 enable-method 17 OF: OF_FND 0 /cpus/cpu@1 reg 4 OF: OF_FND 0 /cpus/cpu@2 reg 4 OF: OF_FND 0 /cpus/cpu@3 reg 4 ...

  5. OF_FND - message format Fields: - pr_fmt() prefix - 'OF_FND' - status - full node name - property name - size of property OF: OF_FND 0 /cpus/cpu@0 reg 4 OF: OF_FND 0 /cpus/cpu@0 enable-method 17 OF: OF_FND 0 /cpus/cpu@1 reg 4

  6. OF_FND - status values Values returned by the property access API 0 success -22 EINVAL -61 ENODATA -75 EOVERFLOW -84 EILSEQ Values for internal use of OF_FND tools 1 OF_FND_IGNORE_BEGIN 2 OF_FND_IGNORE_END

  7. Using OF_FND messages OF_FND messages can be manually examined for debugging purposes.

  8. Boot Console - flood of messages $ grep OF_FND console | wc -l 17963

  9. Boot Console - flood of messages $ grep OF_FND console | wc -l 17963 I will reduce the flood of messages to just one node. This simple node can provide some insights in how to use the OF_FND messages.

  10. Boot Console - reduce flood (1) (1) Reduce flood of messages to just one node. $ grep OF_FND console | grep coincell | sort -u OF: OF_FND 0 /soc/spmi@fc4cf000/pm8941@0/coincell@2800 compatible 21 OF: OF_FND 0 /soc/spmi@fc4cf000/pm8941@0/coincell@2800 name 9 OF: OF_FND 0 /soc/spmi@fc4cf000/pm8941@0/coincell@2800 status 8 OF: OF_FND -22 /soc/spmi@fc4cf000/pm8941@0/coincell@2800 device_type 0

  11. Boot Console - reduce flood (2a) (2a) Will remove node name path prefix $ grep OF_FND console | grep coincell | sort -u OF: OF_FND 0 /soc/spmi@fc4cf000/pm8941@0/ coincell@2800 compatible 21 OF: OF_FND 0 /soc/spmi@fc4cf000/pm8941@0/ coincell@2800 name 9 OF: OF_FND 0 /soc/spmi@fc4cf000/pm8941@0/ coincell@2800 status 8 OF: OF_FND -22 /soc/spmi@fc4cf000/pm8941@0/ coincell@2800 device_type 0

  12. Boot Console - reduced flood (2b) (2b) Remove node name path prefix $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0

  13. Boot Console - reduced flood (2b) (2b) Remove node name path prefix $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 The result is a format that fits well on subsequent slides in this presentation.

  14. Compare OF_FND to .dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  15. Compare OF_FND to .dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell@2800 { compatible = " qcom,pm8941-coincell "; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  16. Compare OF_FND to .dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell @2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  17. property “name” Deprecated, will not appear in the .dtb If the “name” property occurs in the .dts, the dtc (compiler) will remove it in function check_name_properties(). In the Linux kernel, the unflatten_device_tree() code will create the “name” property from the node name in function populate_properties().

  18. Compare OF_FND to .dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = " disable "; };

  19. Compare OF_FND to .dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  20. Compare OF_FND to .dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 TROUBLE IN PARADISE: I failed to remove the messages during the unflatten_device_tree() processing. All of the examples in this presentation that use grep will have some extra properties in the console output.

  21. Summarize - in dts, accessed OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell @2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  22. Summarize - in dts, not accessed OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  23. Summarize - not in dts OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 status 8 OF: OF_FND -22 coincell@2800 device_type 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "disable"; };

  24. Automation This simple node was not too difficult to examine, but imagine repeating the process for the entire device tree (1062 lines for this example device tree)

  25. scripts/dtc/dt_prop A new tool to automate the comparison of the OF_FND property access messages to the device tree source.

  26. scripts/dtc/dt_prop $ scripts/dtc/dt_prop --help Usage: dt_prop TARGET_LOG DTx Report differences between properties accessed on the target system (reported in TARGET_LOG) and properties that are in DTx.

  27. dt_prop - (redacted example) $ dt_prop --all-prop \ --node-match coincell \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { compatible = <>; - interrupts; - interrupts-extended; + qcom,charge-enable; - qcom,charger-disable;

  28. dt_prop - (redacted example) Looks suspiciously similar to the output of dtx_diff

  29. dt_prop - algorithm (1) Looks suspiciously similar to the output of dtx_diff - Generate dts_target_1 For each OF_FND message, add a line to this device tree source, providing the node and property.

  30. dts_target_1 /dts-v1/; /{chosen{stdout-path = <0>;};}; /{cpus{cpu@0{reg = <0>;};};}; /{cpus{cpu@0{enable-method = <0>;};};}; /{cpus{cpu@1{reg = <0>;};};}; /{cpus{cpu@2{reg = <0>;};};}; /{cpus{cpu@3{reg = <0>;};};};

  31. dt_prop - algorithm (2) Looks suspiciously similar to the output of dtx_diff - Generate dts_target_1 For each OF_FND message, add a line to this device tree source, providing the node and property. - dtx_diff dts_target_1 >dts_target_2

  32. dt_prop - algorithm (3) Looks suspiciously similar to the output of dtx_diff - Generate dts_target_1 For each OF_FND message, add a line to this device tree source, providing the node and property. - dtx_diff dts_target_1 >dts_target_2 - dtx_diff DTx >dts_dtx

  33. dt_prop - algorithm (4) Looks suspiciously similar to the output of dtx_diff - Generate dts_target_1 For each OF_FND message, add a line to this device tree source, providing the node and property. - dtx_diff dts_target_1 >dts_target_2 - dtx_diff Dtx >dts_dtx - scripts/dtc/dts_diff dts_target_2 dts_dtx

  34. dt_prop - differences only $ dt_prop --node-match coincell \ \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; };

  35. dt_prop - all properties $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { compatible = <>; + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; status = <>; };

  36. dt_prop - in dts, accessed $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { compatible = <>; + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; status = <>; };

  37. dt_prop - in dts, not accessed $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { compatible = <>; + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; status = <>; };

  38. dt_prop - not in dts (none) $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { compatible = <>; + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; status = <>; };

  39. dt_prop - disabled nodes Property values are redacted, so the value of the status property from dt_prop can not be used to determine if the node is disabled. In this example, the .dts contains: status = “disable”; # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { compatible = <>; + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; status = <>; };

  40. dt_prop - disabled nodes $ dt_prop --node-match coincell \ --all-prop --tag-disabled \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts // ***** node disabled ***** coincell@2800 { compatible = <>; + qcom,charge-enable; + qcom,rset-ohms = <>; + qcom,vset-millivolts = <>; + reg = <>; status = <>; };

  41. Complicate the example Change status from “disabled” to “ok” to enable the node.

  42. Complicate the example Change status from “disabled” to “ok” to enable the node. You should expect the driver probe function to access more properties.

  43. Changes from status = “disabled” $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 qcom,rset-ohms 4 OF: OF_FND 0 coincell@2800 qcom,vset-millivolts 4 OF: OF_FND 0 coincell@2800 reg 4 OF: OF_FND 0 coincell@2800 status 3 OF: OF_FND -22 coincell@2800 assigned-clock-parents 0 OF: OF_FND -22 coincell@2800 assigned-clock-rates 0 OF: OF_FND -22 coincell@2800 device_type 0 OF: OF_FND -22 coincell@2800 dma-coherent 0 OF: OF_FND -22 coincell@2800 interrupts 0 OF: OF_FND -22 coincell@2800 interrupts-extended 0 OF: OF_FND -22 coincell@2800 msi-parent 0 OF: OF_FND -22 coincell@2800 pinctrl-0 0 OF: OF_FND -22 coincell@2800 power-domains 0 OF: OF_FND -22 coincell@2800 qcom,charger-disable 0 OF: OF_FND -22 coincell@2800 reg-names 0 OF: OF_FND -22 coincell@2800 samsung,power-domain 0

  44. Compare OF_FND to .dts $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 qcom,rset-ohms 4 OF: OF_FND 0 coincell@2800 qcom,vset-millivolts 4 OF: OF_FND 0 coincell@2800 reg 4 OF: OF_FND 0 coincell@2800 status 3 OF: OF_FND -22 coincell@2800 assigned-clock-parents 0 OF: OF_FND -22 coincell@2800 assigned-clock-rates 0 OF: OF_FND -22 coincell@2800 device_type 0 OF: OF_FND -22 coincell@2800 dma-coherent 0 OF: OF_FND -22 coincell@2800 interrupts 0 OF: OF_FND -22 coincell@2800 interrupts-extended 0 OF: OF_FND -22 coincell@2800 msi-parent 0 OF: OF_FND -22 coincell@2800 pinctrl-0 0 OF: OF_FND -22 coincell@2800 power-domains 0 OF: OF_FND -22 coincell@2800 qcom,charger-disable 0 OF: OF_FND -22 coincell@2800 reg-names 0 OF: OF_FND -22 coincell@2800 samsung,power-domain 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "ok"; };

  45. Summarize - in dts, accessed $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 qcom,rset-ohms 4 OF: OF_FND 0 coincell@2800 qcom,vset-millivolts 4 OF: OF_FND 0 coincell@2800 reg 4 OF: OF_FND 0 coincell@2800 status 3 OF: OF_FND -22 coincell@2800 assigned-clock-parents 0 OF: OF_FND -22 coincell@2800 assigned-clock-rates 0 OF: OF_FND -22 coincell@2800 device_type 0 OF: OF_FND -22 coincell@2800 dma-coherent 0 OF: OF_FND -22 coincell@2800 interrupts 0 OF: OF_FND -22 coincell@2800 interrupts-extended 0 OF: OF_FND -22 coincell@2800 msi-parent 0 OF: OF_FND -22 coincell@2800 pinctrl-0 0 OF: OF_FND -22 coincell@2800 power-domains 0 OF: OF_FND -22 coincell@2800 qcom,charger-disable 0 OF: OF_FND -22 coincell@2800 reg-names 0 OF: OF_FND -22 coincell@2800 samsung,power-domain 0 coincell @2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "ok"; };

  46. Summarize - in dts, not accessed $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 qcom,rset-ohms 4 OF: OF_FND 0 coincell@2800 qcom,vset-millivolts 4 OF: OF_FND 0 coincell@2800 reg 4 OF: OF_FND 0 coincell@2800 status 3 OF: OF_FND -22 coincell@2800 assigned-clock-parents 0 OF: OF_FND -22 coincell@2800 assigned-clock-rates 0 OF: OF_FND -22 coincell@2800 device_type 0 OF: OF_FND -22 coincell@2800 dma-coherent 0 OF: OF_FND -22 coincell@2800 interrupts 0 OF: OF_FND -22 coincell@2800 interrupts-extended 0 OF: OF_FND -22 coincell@2800 msi-parent 0 OF: OF_FND -22 coincell@2800 pinctrl-0 0 OF: OF_FND -22 coincell@2800 power-domains 0 OF: OF_FND -22 coincell@2800 qcom,charger-disable 0 OF: OF_FND -22 coincell@2800 reg-names 0 OF: OF_FND -22 coincell@2800 samsung,power-domain 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "ok"; };

  47. Summarize - not in dts $ grep OF_FND console | grep coincell | sort -u \ | sed -e 's|\/.*\/||' OF: OF_FND 0 coincell@2800 compatible 21 OF: OF_FND 0 coincell@2800 name 9 OF: OF_FND 0 coincell@2800 qcom,rset-ohms 4 OF: OF_FND 0 coincell@2800 qcom,vset-millivolts 4 OF: OF_FND 0 coincell@2800 reg 4 OF: OF_FND 0 coincell@2800 status 3 OF: OF_FND -22 coincell@2800 assigned-clock-parents 0 OF: OF_FND -22 coincell@2800 assigned-clock-rates 0 OF: OF_FND -22 coincell@2800 device_type 0 OF: OF_FND -22 coincell@2800 dma-coherent 0 OF: OF_FND -22 coincell@2800 interrupts 0 OF: OF_FND -22 coincell@2800 interrupts-extended 0 OF: OF_FND -22 coincell@2800 msi-parent 0 OF: OF_FND -22 coincell@2800 pinctrl-0 0 OF: OF_FND -22 coincell@2800 power-domains 0 OF: OF_FND -22 coincell@2800 qcom,charger-disable 0 OF: OF_FND -22 coincell@2800 reg-names 0 OF: OF_FND -22 coincell@2800 samsung,power-domain 0 coincell@2800 { compatible = "qcom,pm8941-coincell"; qcom,charge-enable; qcom,rset-ohms = <0x834>; qcom,vset-millivolts = <0xbb8>; reg = <0x2800>; status = "ok"; };

  48. dt_prop - differences only $ dt_prop --node-match coincell \ \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - assigned-clock-parents; - assigned-clock-rates; - dma-coherent; - interrupts; - interrupts-extended; - msi-parent; - pinctrl-0; - power-domains; + qcom,charge-enable; - qcom,charger-disable; - reg-names; - samsung,power-domain; };

  49. dt_prop - all properties $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - assigned-clock-parents; - assigned-clock-rates; compatible = <>; - dma-coherent; - interrupts; - interrupts-extended; - msi-parent; - pinctrl-0; - power-domains; + qcom,charge-enable; - qcom,charger-disable; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; - reg-names; - samsung,power-domain; status = <>; };

  50. dt_prop - in dts, accessed $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - assigned-clock-parents; - assigned-clock-rates; compatible = <>; - dma-coherent; - interrupts; - interrupts-extended; - msi-parent; - pinctrl-0; - power-domains; + qcom,charge-enable; - qcom,charger-disable; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; - reg-names; - samsung,power-domain; status = <>; };

  51. dt_prop - in dts, not accessed $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - assigned-clock-parents; - assigned-clock-rates; compatible = <>; - dma-coherent; - interrupts; - interrupts-extended; - msi-parent; - pinctrl-0; - power-domains; + qcom,charge-enable ; - qcom,charger-disable; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; - reg-names; - samsung,power-domain; status = <>; };

  52. dt_prop - not in dts $ dt_prop --node-match coincell \ --all-prop \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - assigned-clock-parents ; - assigned-clock-rates ; compatible = <>; - dma-coherent ; - interrupts ; - interrupts-extended ; - msi-parent ; - pinctrl-0 ; - power-domains ; + qcom,charge-enable; - qcom,charger-disable ; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; - reg-names ; - samsung,power-domain ; status = <>; };

  53. Driver - source What property accesses should we expect from reading the driver?

  54. Driver - source # drivers/misc/qcom-coincell.c: qcom_coincell_probe() of_property_read_u32(, "reg", ) of_property_read_bool(, "qcom,charger-disable") of_property_read_u32(, "qcom,rset-ohms", ) of_property_read_u32(, "qcom,vset-millivolts", )

  55. accessed by driver coincell@2800 { ... compatible = <>; ... + qcom,charge-enable; - qcom,charger-disable ; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; ... status = <>; };

  56. not accessed by kernel coincell@2800 { ... compatible = <>; ... + qcom,charge-enable ; - qcom,charger-disable; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; ... status = <>; };

  57. not accessed by kernel BUG! coincell@2800 { ... compatible = <>; ... + qcom,charge-enable ; - qcom,charger-disable ; qcom,rset-ohms = <>; qcom,vset-millivolts = <>; reg = <>; ... status = <>; }; I carried forward an old patch that added the coincell node to the .dtsi. The old patch had a property for a previous version of the driver.

  58. Sidetrack: something odd skip $ dt_prop --node-match coincell \ console \ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - assigned-clock-parents; - assigned-clock-rates; - dma-coherent; - interrupts; - interrupts-extended; - msi-parent; - pinctrl-0; - power-domains; + qcom,charge-enable; - qcom,charger-disable; - reg-names; - samsung,power-domain; };

  59. Sidetrack: something odd... skip # --- console # +++ arch/arm/boot/dts/qcom-apq8074-dragonboard.dts coincell@2800 { - samsung,power-domain; }; A Samsung related property access attempted for a device that is a Qualcomm SOC device.

  60. samsung,power-domain skip binding document: bindings/display/exynos/exynos7-decon.txt Device-Tree bindings for Samsung Exynos7 SoC display controller (DECON)

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