Messages in this thread | | | Subject | Re: [PATCH v3 02/19] hwmon: (mr75203) fix VM sensor allocation when "intel, vm-map" not defined | Date | Thu, 1 Sep 2022 18:24:51 +0300 | From | "Farber, Eliav" <> |
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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.
> 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.
-- Regards, Eliav
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