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SubjectRe: [PATCH v3 5/5] mtd: spi-nor: cadence-quadspi: Add runtime PM support
From
Date
Hi,

On 9/28/2017 8:31 PM, matthew.gerlach@linux.intel.com wrote:
>
> Hi Vignesh,
>
> I tried this patch on an Arria10 SOCFPGA devkit against the 4.1.33-ltsi
> kernel, and it did not go well. Commands to the flash chip timedout
> resulting in the probe function failing. I ran into other problems, not
> related to cadence-quadspi, that prevented me from testing against 4.9 and
> 4.12 kernels, but I suspect similar behavior.
>

Ok, thanks! I will keep the clk_*() calls for now.

Regards
Vignesh
> Matthew Gerlach
>
> On Wed, 27 Sep 2017, Vignesh R wrote:
>
>> Hi Matthew,
>>
>> On Tuesday 26 September 2017 05:19 AM, Marek Vasut wrote:
>> [...]
>>>>>> Ok thanks! Do you know if pm_runtime_get_sync() can enable clocks for
>>>>>> QSPI on SoCFPGA or if clk_prepare_enable() is needed? Just trying to see
>>>>>> if its possible to get rid of clk_*() calls in favor of pm_*() calls.
>>>>>
>>>>> Not of the top of my head, sorry. +CC Matthew, he should know.
>>>>
>>>> I am not an expert at the clock framework nor the power management, but I
>>>> did ask around a bit.  No one I asked was planning to change the clk_*()
>>>> calls to pm_*() call, but the feedback was that it would be a good idea.
>>>
>>> The question is, if we do the replacement, will it break on socfpga ?
>>> A quick test might be useful.
>>>
>>
>> yes, a quick qspi test with clk_prepare_enable() replaced by pm_*() calls
>> like below patch would be helpful:
>>
>>
>> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
>> index 53c7d8e0327a..7ad3e176cc88 100644
>> --- a/drivers/mtd/spi-nor/cadence-quadspi.c
>> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
>> @@ -34,6 +34,7 @@
>> #include <linux/sched.h>
>> #include <linux/spi/spi.h>
>> #include <linux/timer.h>
>> +#include <linux/pm_runtime.h>
>>
>> #define CQSPI_NAME "cadence-qspi"
>> #define CQSPI_MAX_CHIPSELECT 16
>> @@ -1206,11 +1207,8 @@ static int cqspi_probe(struct platform_device *pdev)
>> return -ENXIO;
>> }
>>
>> - ret = clk_prepare_enable(cqspi->clk);
>> - if (ret) {
>> - dev_err(dev, "Cannot enable QSPI clock.\n");
>> - return ret;
>> - }
>> + pm_runtime_enable(dev);
>> + pm_runtime_get_sync(dev);
>>
>> cqspi->master_ref_clk_hz = clk_get_rate(cqspi->clk);
>>
>>
>>
>>
>>
>> --
>> Regards
>> Vignesh
>>
>

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