On Monday 30 October 2017 02:18 PM, Faiz Abbas wrote:
>
>
> On Thursday 26 October 2017 01:29 PM, Faiz Abbas wrote:
>> David,
>>
>> On Thursday 19 October 2017 06:56 PM, David Laight wrote:
>>> From: Faiz Abbas
>>>> Sent: 19 October 2017 14:09
>>>> On Thursday 19 October 2017 06:13 PM, Faiz Abbas wrote:
>>>>> Enable support for printing the LTSSM link state for debugging PCI
>>>>> when link is down.
>>>>>
>>>>> Signed-off-by: Faiz Abbas <faiz_abbas@xxxxxx>
>>>>> ---
>>>>> v2:
>>>>> 1. Changed dev_err() to dev_dbg()
>>>>> 2. Changed static char array to static const char * const
>>>>> 3. format changes
>>>>>
>>>>> drivers/pci/dwc/pci-dra7xx.c | 48 ++++++++++++++++++++++++++++++++++++++++++++
>>>>> 1 file changed, 48 insertions(+)
>>>>>
>>>>> diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
>>>>> index 34427a6..0e70e77 100644
>>>>> --- a/drivers/pci/dwc/pci-dra7xx.c
>>>>> +++ b/drivers/pci/dwc/pci-dra7xx.c
>>>>> @@ -98,6 +98,45 @@ struct dra7xx_pcie_of_data {
>>>>>
>>>>> #define to_dra7xx_pcie(x) dev_get_drvdata((x)->dev)
>>>>>
>>>>> +static const char * const state[] = {
>>>>> + "DETECT_QUIET",
>>> ...
>>>>> + "RCVRY_EQ3"
>>>>> +};
>>>>> +
>>>>> static inline u32 dra7xx_pcie_readl(struct dra7xx_pcie *pcie, u32 offset)
>>>>> {
>>>>> return readl(pcie->base + offset);
>>>>> @@ -118,6 +157,15 @@ static int dra7xx_pcie_link_up(struct dw_pcie *pci)
>>>>> {
>>>>> struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci);
>>>>> u32 reg = dra7xx_pcie_readl(dra7xx, PCIECTRL_DRA7XX_CONF_PHY_CS);
>>>>> + u32 cmd_reg;
>>>>> + u32 ltssm_state;
>>>>> +
>>>>> + if (!(reg & LINK_UP)) {
>>>>> + cmd_reg = dra7xx_pcie_readl(dra7xx,
>>>>> + PCIECTRL_DRA7XX_CONF_DEVICE_CMD);
>>>>> + ltssm_state = (cmd_reg & GENMASK(7, 2)) >> 2;
>>>>> + dev_dbg(pci->dev, "Link state:%s\n", state[ltssm_state]);
>>>
>>> Hmmm... GENMASK leaves by hunting header files...> Why not (cmd_reg >> 2) & 63 and explicitly define state[64]
>>> to guarantee that you never print anything worse than a NULL
>>> pointer.
>>
>> I'm not sure what you mean. Are you worried we might print something
>> outside the array bounds? How is this easier to decipher than GENMASK?
>>
>>>
>>>>> + }
>>>>>
>>>>> return !!(reg & LINK_UP);
>>>>> }
>>>>>
>>>>
>>>> I missed David's comment in v1. Will submit a new version. Please ignore.
>>>
>>> I've a 'neat' trick for generating strings that match constants.
>>> You can get the compiler to do all the work for you:
>>> (Assuming I've typed it correctly)
>>>
>>> #define LTSSM_DEFS(x) \
>>> x(DETECT_QUIET) \
>>> x(DETECT_ACT) \
>>> (continue for all the names)
>>>
>>> Define an enum with the named constants:
>>> #define X(name) LTSSM_STATE_##name,
>>> enum (LTSSM_DEFS(X) LTSSM_STATE_SIZE=64);
>>> #undef X
>>>
>>> Array of strings:
>>> #define X(name) [LTSSM_STATE_##name] = #name
>>> static const char * const state_names[LTSSM_STATE_SIZE] = { LTSSM_DEFS(X) };
>>> #undef X
>>>
>>> David
>>>
>>
>> So I implemented your idea and it looks like this:
>> http://pastebin.ubuntu.com/25821834/
>>
>> I don't know how much we gained by adding the trick. I still had to be
>> careful not to be off by 1 when writing the list. Plus we are never
>> saying anything like printk("%s", state[LTSSM_STATE_DETECT_QUIET]. Its a
>> register read which is used to index the list array.
>>
>> Thanks,
>> Faiz
>>
>
> Gentle Ping.
>
Ping Again.
