Re: [RFC v5 1/2] mmc: sdhci-msm: Add interconnect bus bandwidth scaling support

[ppvk@codeaurora.org]

On 2020-03-13 02:19, Matthias Kaehlcke wrote:
Hi Matthias,

Thanks for reviewing.

> Hi Pradeep,
> 
> On Thu, Mar 12, 2020 at 11:31:50AM +0530, Pradeep P V K wrote:
>> Add interconnect bandwidths for SDHC driver using OPP framework that
>> is required by SDHC driver based on the clock frequency and bus width
>> of the card. Otherwise, the system clocks may run at minimum clock
>> speed and thus affecting the performance.
>> 
>> This change is based on
>> [RFC] mmc: host: sdhci-msm: Use the interconnect API
>> (https://lkml.org/lkml/2018/10/11/499) and
>> 
>> [PATCH v6] Introduce Bandwidth OPPs for interconnects
>> (https://lkml.org/lkml/2019/12/6/740)
>> 
>> Co-developed-by: Sahitya Tummala <stummala@codeaurora.org>
>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
>> Co-developed-by: Subhash Jadavani <subhashj@codeaurora.org>
>> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
>> Co-developed-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
>> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
>> Co-developed-by: Pradeep P V K <ppvk@codeaurora.org>
>> Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
>> ---
>> 
>> RFC v4 -> v5:
>> - Rewrote the icc interconnect get handlers and its error handling
>>   and allocated vote data after handling all icc get handler errors.
>> - Removed explicit error check on ICC handlers.
>> - Addressed minor code style comments.
>> 
>>  drivers/mmc/host/sdhci-msm.c | 231 
>> ++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 227 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/mmc/host/sdhci-msm.c 
>> b/drivers/mmc/host/sdhci-msm.c
>> index 09ff731..5fe8fad 100644
>> --- a/drivers/mmc/host/sdhci-msm.c
>> +++ b/drivers/mmc/host/sdhci-msm.c
>> 
>> ...
>> 
>> +/*
>> + * This function sets the interconnect bus bandwidth
>> + * vote based on bw (bandwidth) argument.
>> + */
>> +#define BUS_INTERCONNECT_PATHS 2 /* 1. sdhc -> ddr 2. cpu -> sdhc */
>> +static void sdhci_msm_bus_set_vote(struct sdhci_host *host,
>> +						unsigned int bw)
>> +{
>> +	int i, err;
>> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>> +	struct sdhci_msm_bus_vote_data *vote_data = msm_host->bus_vote_data;
>> +	struct device *dev = &msm_host->pdev->dev;
>> +	struct dev_pm_opp *opp;
>> +	unsigned long freq = bw;
>> +	unsigned long peak_bw[BUS_INTERCONNECT_PATHS] = {0};
>> +	unsigned long avg_bw[BUS_INTERCONNECT_PATHS] = {0};
>> +
>> +	if (bw == vote_data->curr_freq)
>> +		return;
>> +
>> +	for (i = 0; i < BUS_INTERCONNECT_PATHS; i++) {
>> +		opp = sdhci_msm_find_opp_for_freq(msm_host, freq);
>> +		if (opp) {
>> +			avg_bw[i] = dev_pm_opp_get_bw(opp, &peak_bw[i]);
>> +			freq += 1; /* Next bandwidth vote */
>> +			dev_pm_opp_put(opp);
>> +		}
>> +	}
>> +	pr_debug("%s: freq:%d sdhc_to_ddr avg_bw:%lu peak_bw:%lu cpu_to_sdhc 
>> avg_bw:%lu peak_bw:%lu\n",
>> +			mmc_hostname(host->mmc), bw, avg_bw[0], peak_bw[0],
>> +				avg_bw[1], peak_bw[1]);
>> +	err = icc_set_bw(vote_data->sdhc_to_ddr, 0, peak_bw[0]);
>> +	if (err) {
>> +		dev_err(dev, "icc_set() failed for 'sdhc-ddr' path err:%d\n",
>> +							err);
> 
> nit: the alignment is odd, either align with 'dev' or a tab after 
> 'dev_err'
> 
sure, will do this in my next patch set.
>> +		return;
>> +	}
>> +	err = icc_set_bw(vote_data->cpu_to_sdhc, 0, peak_bw[1]);
>> +	if (err) {
>> +		dev_err(dev, "icc_set() failed for 'cpu-sdhc' path err:%d\n",
>> +							err);
> 
> ditto
> 
ok.

>> +		return;
>> +	}
>> +	vote_data->curr_freq = bw;
>> +}
>> +
>> +/*
>> + * Helper function to register for OPP and interconnect
>> + * frameworks.
>> + */
>> +static struct sdhci_msm_bus_vote_data
>> +		*sdhci_msm_bus_register(struct sdhci_msm_host *host,
>> +				struct platform_device *pdev)
>> +{
>> +	struct sdhci_msm_bus_vote_data *vote_data;
>> +	struct device *dev = &pdev->dev;
>> +	int ret, i, err;
> 
> nit: you can get rid of 'ret' and use 'err' instead.
> 
ok. i will do this in my next patchset.

>> +	struct icc_path *icc_paths[BUS_INTERCONNECT_PATHS];
>> +	const char *path_names[] = {
>> +		"sdhc-ddr",
>> +		"cpu-sdhc",
>> +	};
>> +
>> +	for (i = 0; i < BUS_INTERCONNECT_PATHS; i++)
>> +		icc_paths[i] = of_icc_get(&pdev->dev, path_names[i]);
>> +
>> +	if (!icc_paths[0] && !icc_paths[1]) {
>> +		dev_info(&pdev->dev, "ICC DT property is missing.Skip vote!!\n");
>> +		return NULL;
>> +	}
>> +
>> +	for (i = 0; i < BUS_INTERCONNECT_PATHS; i++) {
>> +		if (!icc_paths[i]) {
>> +			dev_err(&pdev->dev, "interconnect path '%s' is not configured\n",
>> +					path_names[i]);
>> +			err = -EINVAL;
>> +			goto handle_err;
>> +		}
>> +		if (IS_ERR(icc_paths[i])) {
>> +			err = PTR_ERR(icc_paths[i]);
>> +
>> +			if (err != -EPROBE_DEFER)
>> +				dev_err(&pdev->dev, "interconnect path '%s' is invalid:%d\n",
>> +					path_names[i], err);
>> +			goto handle_err;
>> +		}
>> +	}
>> +
>> +	ret = dev_pm_opp_of_add_table(dev);
>> +	if (ret) {
>> +		if (ret == -ENODEV || ret == -ENODATA)
>> +			dev_err(dev, "OPP dt properties missing:%d\n", ret);
>> +		else
>> +			dev_err(dev, "OPP registration failed:%d\n", ret);
> 
> need to call icc_put() for the two paths?
> 
hmm yes. coming here means, we got both icc paths without error.
So, should put both icc paths. I will handle this by adding a new goto 
jump tag.

>> +		return ERR_PTR(ret);
>> +	}
>> +
>> +	vote_data = devm_kzalloc(dev, sizeof(*vote_data), GFP_KERNEL);
>> +	if (!vote_data)
> 
> ditto
> 
> probably you want to do this with a jump to an error handler below.
> 
ok. i will handle this by adding a new goto jump tag.

>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	vote_data->sdhc_to_ddr = icc_paths[0];
>> +	vote_data->cpu_to_sdhc = icc_paths[1];
>> +	return vote_data;
> 
> nit: add empty line
> 
ok.

>> +handle_err:
>> +	if (err) {
>> +		int other = (i == 0) ? 1 : 0;
>> +
>> +		if (!IS_ERR_OR_NULL(icc_paths[other]))
>> +			icc_put(icc_paths[other]);
>> +	}
> 
> doing this at the end (as opposed to my suggestion from
> https://patchwork.kernel.org/patch/11388409/#23165321) has the 
> advantage of
> keeping the above loop cleaner from error handling cruft, on the 
> downside it
> is probably easier to understand right away in the context of the loop. 
> I
> guess you can do it either way.
> 
True. i will leave this error handling at bottom as the code looks more 
cleaner.

> It might get a bit more messy if you also handle the case where both 
> paths are
> valid. If that gets too involved I'd suggest to hnadle the above case 
> inside
> the loop.
> 
hmm true, handling the above error in loop making the code more messy 
so,
i'm using a new tag (put_icc) to put both the icc paths.

>> +	return ERR_PTR(err);
>> +}
>> +
>> +static void sdhci_msm_bus_unregister(struct device *dev,
>> +				struct sdhci_msm_host *host)
>> +{
>> +	struct sdhci_msm_bus_vote_data *vote_data = host->bus_vote_data;
>> +
>> +	if (IS_ERR_OR_NULL(vote_data))
> 
> I think 'if (!vote_data)' would be sufficient, since _probe() aborts in
> case of an error.
> 
ok. i will handle this in my next patch set.

>> +		return;
>> +
>> +	icc_put(vote_data->sdhc_to_ddr);
>> +	icc_put(vote_data->cpu_to_sdhc);
>> +}
>> +
>> +static void sdhci_msm_bus_voting(struct sdhci_host *host, bool 
>> enable)
>> +{
>> +	struct mmc_ios *ios = &host->mmc->ios;
>> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>> +	unsigned int bw;
>> +
>> +	if (IS_ERR_OR_NULL(msm_host->bus_vote_data))
>> +		return;
> 
> ditto
ok.