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Subject: Re: [alsa-devel] [RFC PATCH 27/40] soundwire: Add Intel resource
 management algorithm
To:     Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Cc:     alsa-devel@alsa-project.org, tiwai@suse.de,
        gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        vkoul@kernel.org, broonie@kernel.org,
        srinivas.kandagatla@linaro.org, jank@cadence.com,
        slawomir.blauciak@intel.com, Sanyog Kale <sanyog.r.kale@intel.com>
References: <20190725234032.21152-1-pierre-louis.bossart@linux.intel.com>
 <20190725234032.21152-28-pierre-louis.bossart@linux.intel.com>
 <20190726154322.GJ16003@ubuntu>
From:   Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Message-ID: <38a1f82f-0069-20a8-35d8-cd29b0d4b2ab@linux.intel.com>
Date:   Fri, 26 Jul 2019 12:55:23 -0500
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Thanks Guennadi for looking at this code, it's hard to review and figure 
things out...
I replied to each, even trivial ones, to have a trace of all the issues.

>> +static void sdw_compute_slave_ports(struct sdw_master_runtime *m_rt,
>> +				    struct sdw_transport_data *t_data)
>> +{
>> +	struct sdw_slave_runtime *s_rt = NULL;
> 
> Superfluous initialisation.

ok

> 
>> +	struct sdw_port_runtime *p_rt;
>> +	int port_bo, sample_int;
>> +	unsigned int rate, bps, ch = 0;
> 
> ditto for ch

ok

>> +
>> +	port_bo = t_data->block_offset;
>> +
>> +	list_for_each_entry(s_rt, &m_rt->slave_rt_list, m_rt_node) {
>> +		rate = m_rt->stream->params.rate;
>> +		bps = m_rt->stream->params.bps;
>> +		sample_int = (m_rt->bus->params.curr_dr_freq / rate);
>> +
>> +		list_for_each_entry(p_rt, &s_rt->port_list, port_node) {
>> +			ch = sdw_ch_mask_to_ch(p_rt->ch_mask);
>> +
>> +			sdw_fill_xport_params(&p_rt->transport_params,
>> +					      p_rt->num, true,
>> +					      SDW_BLK_GRP_CNT_1,
>> +					      sample_int, port_bo, port_bo >> 8,
>> +					      t_data->hstart,
>> +					      t_data->hstop,
> 
> I think the above two lines could fit in one

likely yes.

> 
>> +					      (SDW_BLK_GRP_CNT_1 * ch), 0x0);
> 
> superfluous parentheses

yep


>> +static void sdw_compute_master_ports(struct sdw_master_runtime *m_rt,
>> +				     struct sdw_group_params *params,
>> +				     int port_bo, int hstop)
>> +{
>> +	struct sdw_transport_data t_data = {0};
>> +	struct sdw_port_runtime *p_rt;
>> +	struct sdw_bus *bus = m_rt->bus;
>> +	int sample_int, hstart = 0;
> 
> superfluous initialisation

yes

> 
>> +	unsigned int rate, bps, ch, no_ch;
>> +
>> +	rate = m_rt->stream->params.rate;
>> +	bps = m_rt->stream->params.bps;
>> +	ch = m_rt->ch_count;
>> +	sample_int = (bus->params.curr_dr_freq / rate);
> 
> superfluous parentheses

yes

>> +
>> +	if (rate != params->rate)
>> +		return;
>> +
>> +	t_data.hstop = hstop;
>> +	hstart = hstop - params->hwidth + 1;
>> +	t_data.hstart = hstart;
>> +
>> +	list_for_each_entry(p_rt, &m_rt->port_list, port_node) {
>> +		no_ch = sdw_ch_mask_to_ch(p_rt->ch_mask);
>> +
>> +		sdw_fill_xport_params(&p_rt->transport_params, p_rt->num,
>> +				      true, SDW_BLK_GRP_CNT_1, sample_int,
>> +				      port_bo, port_bo >> 8, hstart, hstop,
>> +				      (SDW_BLK_GRP_CNT_1 * no_ch), 0x0);
> 
> superfluous parentheses

yes

> 
>> +
>> +		sdw_fill_port_params(&p_rt->port_params,
>> +				     p_rt->num, bps,
>> +				     SDW_PORT_FLOW_MODE_ISOCH,
>> +				     SDW_PORT_DATA_MODE_NORMAL);
>> +
>> +		/* Check for first entry */
>> +		if (!(p_rt == list_first_entry(&m_rt->port_list,
>> +					       struct sdw_port_runtime,
>> +					       port_node))) {
> 
> you wanted to write "if (p_rt != ...)"

bad code indeed, thanks for spotting this. I need to double-check this 
one, now I don't trust the ==
it could also be that it was meant to be a NULL check on the first entry.

> 
>> +			port_bo += bps * ch;
>> +			continue;
>> +		}
>> +
>> +		t_data.hstart = hstart;
>> +		t_data.hstop = hstop;
> 
> You already set these two above

need to check this as well.

> 
>> +		t_data.block_offset = port_bo;
>> +		t_data.sub_block_offset = 0;
>> +		port_bo += bps * ch;
>> +	}
>> +
>> +	sdw_compute_slave_ports(m_rt, &t_data);
>> +}
>> +
>> +static void _sdw_compute_port_params(struct sdw_bus *bus,
>> +				     struct sdw_group_params *params, int count)
>> +{
>> +	struct sdw_master_runtime *m_rt = NULL;
> 
> superfluous initialisation

yes

> 
>> +	int hstop = bus->params.col - 1;
>> +	int block_offset, port_bo, i;
>> +
>> +	/* Run loop for all groups to compute transport parameters */
>> +	for (i = 0; i < count; i++) {
>> +		port_bo = 1;
>> +		block_offset = 1;
>> +
>> +		list_for_each_entry(m_rt, &bus->m_rt_list, bus_node) {
>> +			sdw_compute_master_ports(m_rt, &params[i],
>> +						 port_bo, hstop);
>> +
>> +			block_offset += m_rt->ch_count *
>> +					m_rt->stream->params.bps;
>> +			port_bo = block_offset;
>> +		}
>> +
>> +		hstop = hstop - params[i].hwidth;
> 
> hstop -= ...

yes

> 
>> +	}
>> +}
>> +
>> +static int sdw_compute_group_params(struct sdw_bus *bus,
>> +				    struct sdw_group_params *params,
>> +				    int *rates, int count)
>> +{
>> +	struct sdw_master_runtime *m_rt = NULL;
> 
> ditto

yes

>> +	int sel_col = bus->params.col;
>> +	unsigned int rate, bps, ch;
>> +	int i, column_needed = 0;
>> +
>> +	/* Calculate bandwidth per group */
>> +	for (i = 0; i < count; i++) {
>> +		params[i].rate = rates[i];
>> +		params[i].full_bw = bus->params.curr_dr_freq / params[i].rate;
>> +	}
>> +
>> +	list_for_each_entry(m_rt, &bus->m_rt_list, bus_node) {
>> +		rate = m_rt->stream->params.rate;
>> +		bps = m_rt->stream->params.bps;
>> +		ch = m_rt->ch_count;
>> +
>> +		for (i = 0; i < count; i++) {
>> +			if (rate == params[i].rate)
>> +				params[i].payload_bw += bps * ch;
> 
> I don't know about the algorithm, rates can repeat, right? So you cannot break
> out of the loop here once you found one match?

This code looks wrong. Need to get an intravenous caffeine injection.

> 
>> +		}
>> +	}
>> +
>> +	for (i = 0; i < count; i++) {
>> +		params[i].hwidth = (sel_col *
>> +			params[i].payload_bw + params[i].full_bw - 1) /
>> +			params[i].full_bw;
>> +
>> +		column_needed += params[i].hwidth;
>> +	}
>> +
>> +	if (column_needed > sel_col - 1)
>> +		return -EINVAL;
>> +
>> +	return 0;
>> +}
>> +
>> +static int sdw_add_element_group_count(struct sdw_group *group,
>> +				       unsigned int rate)
>> +{
>> +	int num = group->count;
>> +	int i;
>> +
>> +	for (i = 0; i <= num; i++) {
>> +		if (rate == group->rates[i])
> 
> Are you sure this is correct? You actually check count + 1 rates - from 0
> to count inclusively. I think this isn't what you wanted to do, so my
> proposal below only checks count rates.

I'll have to double check. There's already the warning on krealloc that 
looks suspicious as well.

> 
>> +			break;
>> +
>> +		if (i != num)
>> +			continue;
>> +
>> +		if (group->count >= group->max_size) {
>> +			group->max_size += 1;
>> +			group->rates = krealloc(group->rates,
>> +						(sizeof(int) * group->max_size),
>> +						GFP_KERNEL);
>> +			if (!group->rates)
>> +				return -ENOMEM;
>> +		}
>> +
>> +		group->rates[group->count++] = rate;
>> +	}
> 
> How about this:
> 
> 	for (i = 0; i < num; i++)
> 		if (rate == group->rates[i])
> 			return 0;
> 
> 	if (group->count >= group->max_size) {
> 		group->max_size += 1;
> 		group->rates = krealloc(group->rates,
> 					(sizeof(int) * group->max_size),
> 					GFP_KERNEL);
> 		if (!group->rates)
> 			return -ENOMEM;
> 	}
> 
> 	group->rates[group->count++] = rate;
> 
> 	return 0;

will check offline and see.

>> +
>> +	return 0;
>> +}
>> +
>> +static int sdw_get_group_count(struct sdw_bus *bus,
>> +			       struct sdw_group *group)
>> +{
>> +	struct sdw_master_runtime *m_rt;
>> +	unsigned int rate;
>> +	int ret = 0;
>> +
>> +	group->count = 0;
>> +	group->max_size = SDW_STRM_RATE_GROUPING;
>> +	group->rates = kcalloc(group->max_size, sizeof(int), GFP_KERNEL);
>> +	if (!group->rates)
>> +		return -ENOMEM;
>> +
>> +	list_for_each_entry(m_rt, &bus->m_rt_list, bus_node) {
>> +		rate = m_rt->stream->params.rate;
>> +		if (m_rt == list_first_entry(&bus->m_rt_list,
>> +					     struct sdw_master_runtime,
>> +					     bus_node)) {
>> +			group->rates[group->count++] = rate;
>> +
>> +		} else {
>> +			ret = sdw_add_element_group_count(group, rate);
>> +			if (ret < 0)
> 
> Actually it looks like you should free rates here? I see that not doing this
> makes the caller function below easier, but I'd say this is more error-
> prone... Up to you but I'd go the "safe" way - if it fails, it frees itself,
> if it succeeds - it's freed elsewhere.

good catch, will look into this.

> 
>> +				return ret;
>> +		}
>> +	}
>> +
>> +	return ret;
> 
> I think this will always return 0 here, so you don't need the "ret"
> variable in the function scope, you only need it in the "else"
> scope above.

will check. In general I avoid per-scope declarations.

>> +}
>> +
>> +/**
>> + * sdw_compute_port_params: Compute transport and port parameters
>> + *
>> + * @bus: SDW Bus instance
>> + */
>> +static int sdw_compute_port_params(struct sdw_bus *bus)
>> +{
>> +	struct sdw_group_params *params = NULL;
>> +	struct sdw_group group;
>> +	int ret;
>> +
>> +	ret = sdw_get_group_count(bus, &group);
>> +	if (ret < 0)
>> +		goto out;
>> +
>> +	if (group.count == 0)
>> +		goto out;
>> +
>> +	params = kcalloc(group.count, sizeof(*params), GFP_KERNEL);
>> +	if (!params) {
>> +		ret = -ENOMEM;
>> +		goto out;
>> +	}
>> +
>> +	/* Compute transport parameters for grouped streams */
>> +	ret = sdw_compute_group_params(bus, params,
>> +				       &group.rates[0], group.count);
>> +	if (ret < 0)
>> +		goto out;
>> +
>> +	_sdw_compute_port_params(bus, params, group.count);
>> +
>> +out:
>> +	kfree(params);
>> +	kfree(group.rates);
> 
> Depending whether or not you change the code above, this might change
> too.

will check

>> +static int sdw_compute_bus_params(struct sdw_bus *bus)
>> +{
>> +	unsigned int max_dr_freq, curr_dr_freq = 0;
>> +	struct sdw_master_prop *mstr_prop = NULL;
> 
> superfluous initialisation

yes

>> +	int i, clk_values, ret;
>> +	bool is_gear = false;
>> +	u32 *clk_buf;
>> +
>> +	mstr_prop = &bus->prop;
>> +	if (!mstr_prop)
> 
> this is impossible, it's an address of bus->prop...

Gah, yes.

>> +		return -EINVAL;
>> +
>> +	if (mstr_prop->num_clk_gears) {
>> +		clk_values = mstr_prop->num_clk_gears;
>> +		clk_buf = mstr_prop->clk_gears;
>> +		is_gear = true;
>> +	} else if (mstr_prop->num_clk_freq) {
>> +		clk_values = mstr_prop->num_clk_freq;
>> +		clk_buf = mstr_prop->clk_freq;
>> +	} else {
>> +		clk_values = 1;
>> +		clk_buf = NULL;
>> +	}
>> +
>> +	max_dr_freq = mstr_prop->max_clk_freq * SDW_DOUBLE_RATE_FACTOR;
>> +
>> +	for (i = 0; i < clk_values; i++) {
>> +		if (!clk_buf)
>> +			curr_dr_freq = max_dr_freq;
>> +		else
>> +			curr_dr_freq = (is_gear) ?
> 
> superfluous parentheses
> 
>> +				(max_dr_freq >>  clk_buf[i]) :
> 
> ditto

yes and yes
> 
>> +				clk_buf[i] * SDW_DOUBLE_RATE_FACTOR;
>> +
>> +		if (curr_dr_freq <= bus->params.bandwidth)
>> +			continue;
>> +
>> +		break;
> 
> I think this is raw code, you'd actually want to write this as
> 
> 		if (curr_dr_freq > bus->params.bandwidth)
> 			break;

I saw this before my Summer break and forgot about it. yes it needs to 
be fixed.

>>   
>>   	bus->debugfs = sdw_bus_debugfs_init(bus);
>>   
>> +	if (!bus->compute_params)
>> +		bus->compute_params = &sdw_compute_params;
> 
> I think it is more usual to not use "&" with functions, but it's valid too

yes, will fix


>> +/* Retrieve and return channel count from channel mask */
>> +static inline int sdw_ch_mask_to_ch(int ch_mask)
>> +{
>> +	int c = 0;
> 
> superfluous initialisation

yes

> 
>> +
>> +	for (c = 0; ch_mask; ch_mask >>= 1)
>> +		c += ch_mask & 1;
> 
> isn't there a built-in or something to count set bits... You could use ffs() to
> at least not loop 31 times for 0x80000000

will check