Messages in this thread | | | Date | Thu, 1 Sep 2022 12:25:16 -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 11:36, Farber, Eliav wrote: > On 9/1/2022 8:11 PM, Guenter Roeck wrote: >> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. >> >> >> >> 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. >> > OK. I have added patch #20 to validate that same VM index doesn't appear > more than once in intel,vm-map. > > u32 vm_mask = 0; > > for (i = 0; i < vm_num; i++) { > if (vm_idx[i] >= vm_num || vm_idx[i] == 0xff)
I think "vm_idx[i] >= vm_num && vm_idx[i] != 0xff) should also be invalid, ie.
if (vm_idx[i] == 0xff) break; if (vm_idx[i] >= vm_num) return -EINVAL;
Thanks, Guenter
> break; > > if (vm_mask & BIT(vm_idx[i])) { > dev_err(dev, "Same VM appears more than once in intel,vm-map\n", > vm_idx[i]); > return EINVAL; > } > > vm_mask |= BIT(vm_idx[i]); > } > > >>> >>>> 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 ? > > I can't find any sense in having such a mapping. > Anyway the new patch will not allow it to happen. > > -- > Regards, Eliav >
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