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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id m102sm52695pje.5.2019.10.23.12.10.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 23 Oct 2019 12:10:26 -0700 (PDT) Date: Wed, 23 Oct 2019 12:10:06 -0700 From: Nicolin Chen To: "S.j. Wang" Subject: Re: [PATCH] ASoC: fsl_asrc: refine the setting of internal clock divider Message-ID: <20191023191002.GB16043@Asurada-Nvidia.nvidia.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "alsa-devel@alsa-project.org" , "timur@kernel.org" , "Xiubo.Lee@gmail.com" , "linuxppc-dev@lists.ozlabs.org" , "tiwai@suse.com" , "lgirdwood@gmail.com" , "perex@perex.cz" , "broonie@kernel.org" , "festevam@gmail.com" , "linux-kernel@vger.kernel.org" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 23, 2019 at 06:25:20AM +0000, S.j. Wang wrote: > > On Thu, Oct 17, 2019 at 02:21:08PM +0800, Shengjiu Wang wrote: > > > For P2P output, the output divider should align with the output sample > > > > I think we should avoid "P2P" (or "M2M") keyword in the mainline code as > > we know M2M will never get merged while somebody working with the > > mainline and caring about new feature might be confused. > > Ok. But we still curious that is there a way to upstream m2m? Hmm..I would love to see that happening. Here is an old discussion that you may want to take a look: https://mailman.alsa-project.org/pipermail/alsa-devel/2014-May/076797.html > > It makes sense to me, yet I feel that the delay at the beginning of the audio > > playback might be longer as a compromise. I am okay with this decision > > though... > > > > > The maximum divider of asrc clock is 1024, but there is no judgement > > > for this limitaion in driver, which may cause the divider setting not > > > correct. > > > > > > For non-ideal ratio mode, the clock rate should divide the sample rate > > > with no remainder, and the quotient should be less than 1024. > > > > > > Signed-off-by: Shengjiu Wang > > > @@ -351,7 +352,9 @@ static int fsl_asrc_config_pair(struct fsl_asrc_pair > > *pair) > > > /* We only have output clock for ideal ratio mode */ > > > clk = asrc_priv->asrck_clk[clk_index[ideal ? OUT : IN]]; > > > > > > - div[IN] = clk_get_rate(clk) / inrate; > > > + clk_rate = clk_get_rate(clk); > > > > The fsl_asrc.c file has config.inclk being set to INCLK_NONE and this sets the > > "ideal" in this function to true. So, although we tend to not use ideal ratio > > setting for p2p cases, yet the input clock is still not physically connected, so > > we still use output clock for div[IN] calculation? > > For p2p case, it can be ideal or non-ideal. For non-ideal, we still use > Output clock for div calculation. > > > > > I am thinking something simplier: if we decided not to use ideal ratio for > > "P2P", instead of adding "bool p2p" with the confusing "ideal" in this > > function, could we just set config.inclk to the same clock as the output one > > for "P2P"? By doing so, "P2P" won't go through ideal ratio mode while still > > having a clock rate from the output clock for div[IN] calculation here. > > Bool p2p is to force output rate to be sample rate, no impact to ideal > Ratio mode. I just realized that the function has a bottom part for ideal mode exclusively -- if we treat p2p as !ideal, those configurations will be missing. So you're right, should have an extra boolean variable. > > > > > + rem[IN] = do_div(clk_rate, inrate); > > > + div[IN] = (u32)clk_rate; > > > if (div[IN] == 0) { > > > > Could we check div[IN] and rem[IN] here? Like: > > if (div[IN] == 0 || div[IN] > 1024) { > > pair_err(); > > goto out; > > } > > > > if (!ideal && rem[IN]) { > > pair_err(); > > goto out; > > } > > > > According to your commit log, I think the max-1024 limitation should be > > applied to all cases, not confined to "!ideal" cases right? And we should > > add some comments also, indicating it is limited by hardware. > > For ideal mode, my test result is the divider not impact the output result. > Which means it is ok for ideal mode even divider is not correct... OK. > > > > > pair_err("failed to support input sample rate %dHz by > > asrck_%x\n", > > > inrate, clk_index[ideal ? OUT : IN]); @@ > > > -360,11 +363,20 @@ static int fsl_asrc_config_pair(struct > > > fsl_asrc_pair *pair) > > > > > > clk = asrc_priv->asrck_clk[clk_index[OUT]]; > > > > > > - /* Use fixed output rate for Ideal Ratio mode (INCLK_NONE) */ > > > - if (ideal) > > > - div[OUT] = clk_get_rate(clk) / IDEAL_RATIO_RATE; > > > - else > > > - div[OUT] = clk_get_rate(clk) / outrate; > > > + /* > > > + * When P2P mode, output rate should align with the out samplerate. > > > + * if set too high output rate, there will be lots of Overload. > > > + * When M2M mode, output rate should also need to align with the > > > + out > > > > For this "should", do you actually mean "M2M could also"? Sorry, I'm just > > trying to understand everyting here, not intentionally being picky at words. > > My understanding is that we still keep the ideal ratio setting because > > "M2M" still uses it. > > We use IDEAL_RATIO_RATE as output rate for m2m mode, it likes a > Tricky operation, in order to improve the performance. I think > The correct operation is to use the real output rate, but the performance > Is bad. So it is a compromise. I see. > > > > > + * samplerate, but M2M must use less time to achieve good > > performance. > > > + */ > > > + clk_rate = clk_get_rate(clk); > > > + if (p2p || !ideal) { > > > + rem[OUT] = do_div(clk_rate, outrate); > > > + div[OUT] = clk_rate; > > > + } else { > > > + rem[OUT] = do_div(clk_rate, IDEAL_RATIO_RATE); > > > + div[OUT] = clk_rate; > > > + } > > > > > > if (div[OUT] == 0) { > > > pair_err("failed to support output sample rate %dHz by > > > asrck_%x\n", @@ -372,6 +384,16 @@ static int fsl_asrc_config_pair(struct > > fsl_asrc_pair *pair) > > > return -EINVAL; > > > } > > > > > > + if (!ideal && (div[IN] > 1024 || div[OUT] > 1024 || > > > + rem[IN] != 0 || rem[OUT] != 0)) { > > > + if (!ideal && (div[IN] > 1024 || div[OUT] > 1024 || rem[IN] || > > > + rem[OUT] != 0)) { > > > > So for ideal == true, these limitaions are not applied any more? > > Remember that the "ideal" is true for "p2p == true" cases here. > > No, not applied. for ideal, the div don't impact the output result > Even it is not accurate. I see. > > > > > + pair_err("The divider can't be used for non ideal mode\n"); > > > + return -EINVAL; > > > + } > > > + > > > + /* Divider range is [1, 1024] */ > > > + div[IN] = min_t(u32, 1024, div[IN]); > > > + div[OUT] = min_t(u32, 1024, div[OUT]); > > > > Hmm, this looks like we want to allow ideal ratio cases and p2p cases to > > operate any way, even if the divider wasn't within the range to get the > > in/out rates from the output clock? > > Yes. We still allow the p2p = true, ideal = false. Note that p2p is not > Equal to ideal. Got it. Overall, I feel it's better to have a naming to state the purpose of using ideal configurations without the IDEAL_RATIO_RATE setup. bool use_ideal_rate; And we can put into the asrc_config structure if there's no major problem. So the condition check for the calculation would be: + if (ideal && config->use_ideal_rate) + rem[OUT] = do_div(clk_rate, IDEAL_RATIO_RATE); + else + rem[OUT] = do_div(clk_rate, outrate); + div[OUT] = clk_rate; And for that if (!ideal && div[IN]....rem[OUT]), I feel it would be clear to have them separately, as the existing "div[IN] == 0" and "div[OUT] == 0" checks, so that we can tell users which side of the divider is out of range and what the sample rate and clock rate are. Thanks Nicolin