linux-kernel - Re: [PATCH 03/21] spi: spi-geni-qcom: Use OPP API to set clk/perf state

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Date:   Mon, 13 Apr 2020 19:32:33 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     viresh.kumar@...aro.org, sboyd@...nel.org,
        bjorn.andersson@...aro.org, agross@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Alok Chauhan <alokc@...eaurora.org>,
        Akash Asthana <akashast@...eaurora.org>,
        linux-spi@...r.kernel.org
Subject: Re: [PATCH 03/21] spi: spi-geni-qcom: Use OPP API to set clk/perf
 state


On 4/9/2020 11:50 PM, Matthias Kaehlcke wrote:
> Hi Rajendra,
> 
> On Wed, Apr 08, 2020 at 07:16:29PM +0530, Rajendra Nayak wrote:
>> geni spi needs to express a perforamnce state requirement on CX
>> depending on the frequency of the clock rates. Use OPP table from
>> DT to register with OPP framework and use dev_pm_opp_set_rate() to
>> set the clk/perf state.
>>
>> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
>> Cc: Alok Chauhan <alokc@...eaurora.org>
>> Cc: Akash Asthana <akashast@...eaurora.org>
>> Cc: linux-spi@...r.kernel.org
>> ---
>>   drivers/spi/spi-geni-qcom.c | 14 +++++++++++---
>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
>> index c397242..ce387dc 100644
>> --- a/drivers/spi/spi-geni-qcom.c
>> +++ b/drivers/spi/spi-geni-qcom.c
>> @@ -7,6 +7,7 @@
>>   #include <linux/log2.h>
>>   #include <linux/module.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/pm_opp.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/qcom-geni-se.h>
>>   #include <linux/spi/spi.h>
>> @@ -95,7 +96,6 @@ static int get_spi_clk_cfg(unsigned int speed_hz,
>>   {
>>   	unsigned long sclk_freq;
>>   	unsigned int actual_hz;
>> -	struct geni_se *se = &mas->se;
>>   	int ret;
>>   
>>   	ret = geni_se_clk_freq_match(&mas->se,
>> @@ -112,9 +112,9 @@ static int get_spi_clk_cfg(unsigned int speed_hz,
>>   
>>   	dev_dbg(mas->dev, "req %u=>%u sclk %lu, idx %d, div %d\n", speed_hz,
>>   				actual_hz, sclk_freq, *clk_idx, *clk_div);
>> -	ret = clk_set_rate(se->clk, sclk_freq);
>> +	ret = dev_pm_opp_set_rate(mas->dev, sclk_freq);
>>   	if (ret)
>> -		dev_err(mas->dev, "clk_set_rate failed %d\n", ret);
>> +		dev_err(mas->dev, "dev_pm_opp_set_rate failed %d\n", ret);
>>   	return ret;
>>   }
>>   
>> @@ -553,6 +553,7 @@ static int spi_geni_probe(struct platform_device *pdev)
>>   	if (!spi)
>>   		return -ENOMEM;
>>   
>> +
>>   	platform_set_drvdata(pdev, spi);
>>   	mas = spi_master_get_devdata(spi);
>>   	mas->irq = irq;
>> @@ -561,6 +562,8 @@ static int spi_geni_probe(struct platform_device *pdev)
>>   	mas->se.wrapper = dev_get_drvdata(dev->parent);
>>   	mas->se.base = base;
>>   	mas->se.clk = clk;
>> +	mas->se.opp = dev_pm_opp_set_clkname(&pdev->dev, "se");
> 
> As commented on the serial patch, it seems an error check is needed
> and the OPP table saved in 'struct geni_se' is never used.

right, I explained about the OPP table in the other patch.

> 
>> +	dev_pm_opp_of_add_table(&pdev->dev);
> 
> This function could also fail for multiple reasons, so the return value
> should be checked.
> 
>  From patch "[01/21] opp: Manage empty OPP tables with clk handle" it seems
> ignoring errors is intended to be able to operate when no OPP table is
> specified. But even with that you want to return in case of certain errors,
> like an invalid OPP table, out of memory or -EPROBE_DEFER.

Thats correct, my intention of not checking the errors was in cases where its
optional, and I did not want to break anything with existing DT. I will go back and
check if its indeed possible for it to return a -EPROBE_DEFER and others which
I should handle.

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