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SubjectRe: [PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver
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On Tuesday 08 November 2016 05:13 PM, Arnd Bergmann wrote:
> On Tuesday, November 8, 2016 1:08:31 PM CET Anurup M wrote:
>
>> On Tuesday 08 November 2016 12:32 PM, Tan Xiaojun wrote:
>>> On 2016/11/7 21:26, Arnd Bergmann wrote:
>>>> On Wednesday, November 2, 2016 11:42:46 AM CET Anurup M wrote:
>>>>> From: Tan Xiaojun <tanxiaojun@huawei.com>
>>>>> + /* ensure the djtag operation is done */
>>>>> + do {
>>>>> + djtag_read32_relaxed(regs_base, SC_DJTAG_MSTR_START_EN_EX, &rd);
>>>>> +
>>>>> + if (!(rd & DJTAG_MSTR_START_EN_EX))
>>>>> + break;
>>>>> +
>>>>> + udelay(1);
>>>>> + } while (timeout--);
>>>> This one is obviously not performance critical at all, so use a non-relaxed
>>>> accessor. Same for the other two in this function.
>>>>
>>>> Are these functions ever called from atomic context? If yes, please document
>>>> from what context they can be called, otherwise please consider changing
>>>> the udelay calls into sleeping waits.
>>>>
>>> Yes, this is not reentrant.
>> The read/write functions shall also be called from irq handler (for
>> handling counter overflow).
>> So need to use udelay calls. Shall Document it in v2.
> Ok.
>
>>>>> +static const struct of_device_id djtag_of_match[] = {
>>>>> + /* for hip05(D02) cpu die */
>>>>> + { .compatible = "hisilicon,hip05-cpu-djtag-v1",
>>>>> + .data = (void *)djtag_readwrite_v1 },
>>>>> + /* for hip05(D02) io die */
>>>>> + { .compatible = "hisilicon,hip05-io-djtag-v1",
>>>>> + .data = (void *)djtag_readwrite_v1 },
>>>>> + /* for hip06(D03) cpu die */
>>>>> + { .compatible = "hisilicon,hip06-cpu-djtag-v1",
>>>>> + .data = (void *)djtag_readwrite_v1 },
>>>>> + /* for hip06(D03) io die */
>>>>> + { .compatible = "hisilicon,hip06-io-djtag-v2",
>>>>> + .data = (void *)djtag_readwrite_v2 },
>>>>> + /* for hip07(D05) cpu die */
>>>>> + { .compatible = "hisilicon,hip07-cpu-djtag-v2",
>>>>> + .data = (void *)djtag_readwrite_v2 },
>>>>> + /* for hip07(D05) io die */
>>>>> + { .compatible = "hisilicon,hip07-io-djtag-v2",
>>>>> + .data = (void *)djtag_readwrite_v2 },
>>>>> + {},
>>>>> +};
>>>> If these are backwards compatible, just mark them as compatible in DT,
>>>> e.g. hip06 can use
>>>>
>>>> compatible = "hisilicon,hip06-cpu-djtag-v1", "hisilicon,hip05-cpu-djtag-v1";
>>>>
>>>> so you can tell the difference if you need to, but the driver only has to
>>>> list the oldest one here.
>>>>
>>>> What is the difference between the cpu and io djtag interfaces?
>> On some chips like hip06, the djtag version is different for IO die.
> In what way? The driver doesn't seem to care about the difference.
There is a difference in djtag version of CPU and IO die (in some chips).
For ex: in hip06 djtag for CPU is v1 and for IO is v2.
so they use different readwrite handlers djtag_readwrite_(v1/2).

+ /* for hip06(D03) cpu die */
+ { .compatible = "hisilicon,hip06-cpu-djtag-v1",
+ .data = (void *)djtag_readwrite_v1 },
+ /* for hip06(D03) io die */
+ { .compatible = "hisilicon,hip06-io-djtag-v2",
+ .data = (void *)djtag_readwrite_v2 },


For the same djtag version, there is no difference in handling in the
driver.

Thanks,
Anurup
> Arnd
>

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