Messages in this thread | | | Date | Thu, 1 Sep 2022 10:11:45 -0700 | Subject | Re: [PATCH v3 02/19] hwmon: (mr75203) fix VM sensor allocation when "intel, vm-map" not defined | From | Guenter Roeck <> |
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On 9/1/22 08:24, Farber, Eliav wrote: > On 9/1/2022 5:44 PM, Guenter Roeck wrote: >> On Thu, Sep 01, 2022 at 11:39:58AM +0300, Farber, Eliav wrote: >>> On 8/31/2022 2:48 PM, Guenter Roeck wrote: >>> > On 8/30/22 22:49, Farber, Eliav wrote: >>> > > On 8/31/2022 8:36 AM, Guenter Roeck wrote: >>> > > > On 8/30/22 12:21, Eliav Farber wrote: >>> > > > > Bug fix - in case "intel,vm-map" is missing in device-tree >>> > > > > ,'num' is set >>> > > > > to 0, and no voltage channel infos are allocated. >>> > > > > >>> > > > > Signed-off-by: Eliav Farber <farbere@amazon.com> >>> > > > > --- >>> > > > > drivers/hwmon/mr75203.c | 28 ++++++++++++---------------- >>> > > > > 1 file changed, 12 insertions(+), 16 deletions(-) >>> > > > > >>> > > > > diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c >>> > > > > index 046523d47c29..0e29877a1a9c 100644 >>> > > > > --- a/drivers/hwmon/mr75203.c >>> > > > > +++ b/drivers/hwmon/mr75203.c >>> > > > > @@ -580,8 +580,6 @@ static int mr75203_probe(struct >>> > > > > platform_device *pdev) >>> > > > > } >>> > > > > >>> > > > > if (vm_num) { >>> > > > > - u32 num = vm_num; >>> > > > > - >>> > > > > ret = pvt_get_regmap(pdev, "vm", pvt); >>> > > > > if (ret) >>> > > > > return ret; >>> > > > > @@ -594,30 +592,28 @@ static int mr75203_probe(struct >>> > > > > platform_device *pdev) >>> > > > > ret = device_property_read_u8_array(dev, "intel,vm-map", >>> > > > > pvt->vm_idx, vm_num); >>> > > > > if (ret) { >>> > > > > - num = 0; >>> > > > > + /* >>> > > > > + * Incase intel,vm-map property is not >>> > > > > defined, we >>> > > > > + * assume incremental channel numbers. >>> > > > > + */ >>> > > > > + for (i = 0; i < vm_num; i++) >>> > > > > + pvt->vm_idx[i] = i; >>> > > > > } else { >>> > > > > for (i = 0; i < vm_num; i++) >>> > > > > if (pvt->vm_idx[i] >= vm_num || >>> > > > > - pvt->vm_idx[i] == 0xff) { >>> > > > > - num = i; >>> > > > > + pvt->vm_idx[i] == 0xff) >>> > > > > break; >>> > > > >>> > > > So all vm_idx values from 0x00 to 0xfe would be acceptable ? >>> > > > Does the chip really have that many registers (0x200 + 0x40 + >>> > > > 0x200 * 0xfe) ? >>> > > > Is that documented somewhere ? >>> > > According to the code vm_num is limited to 32 because the mask is >>> > > only 5 bits: >>> > > >>> > > #define VM_NUM_MSK GENMASK(20, 16) >>> > > #define VM_NUM_SFT 16 >>> > > vm_num = (val & VM_NUM_MSK) >> VM_NUM_SFT; >>> > > >>> > > In practice according to the data sheet I have: >>> > > 0 <= VM instances <= 8 >>> > > >>> > Sorry, my bad. I misread the patch and thought the first part of >>> > the if statement was removed. >>> > >>> > Anyway, what is the difference between specifying an vm_idx value of >>> > 0xff and not specifying anything ? Or, in other words, taking the dt >>> > example, the difference between >>> > intel,vm-map = [03 01 04 ff ff]; >>> > and >>> > intel,vm-map = [03 01 04]; >>> >>> The actual number of VMs is read from a HW register: >>> ret = regmap_read(pvt->c_map, PVT_IP_CONFIG, &val); >>> ... >>> vm_num = (val & VM_NUM_MSK) >> VM_NUM_SFT; >>> >>> Also, using: >>> ret = device_property_read_u8_array(dev, "intel,vm-map", vm_idx, >>> vm_num); >>> in the driver will fail if vm_num > sizeof array in device-tree. >>> >>> So, if for example vm_num = 5, but you will want to map only 3 of them >>> you most set property to be: >>> intel,vm-map = [03 01 04 ff ff]; >>> otherwise if you set: >>> intel,vm-map = [03 01 04]; >>> it will assume the property doesn't, and will continue the flow in code >>> as if it doesn’t exist (which is not what the user wanted, and before my >>> fix also has a bug). >> >> There should be some error handling to catch this case (ie if the number >> of entries does not match the expected count), or if a value in the array >> is larger or equal to vm_num. Today the latter is silently handled as end >> of entries (similar to 0xff), but that should result in an error. >> This would avoid situations like >> intel,vm-map = [01 02 03 04 05]; >> ie where the person writing the devicetree file accidentally entered >> index values starting with 1 instead of 0. A mismatch between vm_num >> and the number of entries in the array is silently handled as if there >> was no property at all, which is at the very least misleading and >> most definitely unexpected and should also result in an error. > > > I assume it is possible to tell according to the return value, if property > doesn’t exist at all, or if it does exists and size of array in > device-tree is smaller than vm_num. > In [PATCH v3 17/19] Andy wrote that “code shouldn't be a YAML validator. > Drop this and make sure you have correct DT schema” so I’m a bit confused > if code should validate “intel,bm-map” or if it is the user responsibility. > As this property was not added by me, I prefer not to fix it as part of > this series of patches. >
You are changing the driver all over the place with 19 patches, including this code, but you don't want to add code that validates the devicetree data ? That seems odd.
> >> Also, what happens if the devicetree content is something like the >> following ? Would that be valid ? >> intel,vm-map = [00 01 01 01 01 01]; > > If device-tree content would be: > intel,vm-map = [00 01 01 01 01 01]; > and assuming 16 channels for each VM, the hwmon sub-system will expose 90 > sysfs to read voltage values. > In practice 16 – 31, 32 – 47, 48 – 63, 64 – 89 will all report the same > input signals for VM1. >
Does that make any sense, and is there a valid reason to have a mapping table like the one in this example ?
Thanks, Guenter
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