From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 054F726F297 for ; Tue, 9 Dec 2025 16:41:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.185 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765298510; cv=none; b=hvzQrwwFKX5JwFE3EbeKoMJekAhtW3pZ/+snfPc0G4AId2JYL3CNNqRnH3zTysKfbGdwjoRJAVtsarpREvmxyTwF10hXMSMEkWBFsDKIdlxCZpiFcaGHgEYBAAvrGsz3lTMoXhNLNlt8/mIevogBISOYHQD/MGSoVbznCxxEcVo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765298510; c=relaxed/simple; bh=pwUcd9vjnfMky5WF7d70fAeZu3q9exEvlcE+V881c5c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Ixzspd4bpHQL+F4/40he23qKyJhPnRYVL+ncGHJLIKMzUU3YfQhMT2EV6XLOPAVmafhxcdhoKLjVrjZqRrR/Md57O0/syexpyEODpw+ICt98hM4FMQg0GIJZqPpQvY3NXpzchMnKdw1EmFbm/Z4kjIZz1Wyj7xNu3tryjAarQ94= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Kca7KAqq; arc=none smtp.client-ip=91.218.175.185 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Kca7KAqq" Message-ID: <5c80bead-716a-4528-b614-4b425184a484@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1765298504; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=brszIlAhmsEE/FZSPfwDcpI6p6Nj3AfFbJJ+JF8SUUA=; b=Kca7KAqqY+hh9g3VjD2m7D8kBFWpoJecDxv2IgJAHOr2uG4BqSwmrP99GjdIXdlLQCJajg R8J/DXXewABEc5D7a8UfqjUakAlzTZehLLa3PUDt0d5Yw3v7jvyP2l8XFq2xkImK2VaOIq h+tJpbOLO2zopW39YNcbJblfElaxfew= Date: Tue, 9 Dec 2025 16:41:39 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3] soundwire: stream: Prepare ports in parallel to reduce stream start latency To: Richard Fitzgerald , vkoul@kernel.org, yung-chuan.liao@linux.intel.com Cc: linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, patches@opensource.cirrus.com References: <20251125165609.483763-1-rf@opensource.cirrus.com> <4d811207-1c01-4302-85b1-9d4079ea1a4b@linux.dev> <795fd33c-7a0f-4600-87be-1690cb0c0ea3@opensource.cirrus.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Pierre-Louis Bossart In-Reply-To: <795fd33c-7a0f-4600-87be-1690cb0c0ea3@opensource.cirrus.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT >>> Changes in V2: >>> +    if (simple_ch_prep_sm) >>> +        return 0; >>> + >>> +    /* >>> +     * Check if already prepared. Avoid overhead of waiting for interrupt >>> +     * and port_ready completion if we don't need to. >>> +     */ 1. >>> +    val = sdw_read_no_pm(s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num)); >>> +    if (val < 0) { >>> +        ret = val; >>> +        goto err; >>> +    } >>> + >>> +    if (val & p_rt->ch_mask) { >> >> Can you explain why we don't use the ch_mask in the already-prepared case? I am missing something. >> > I'm not sure what you mean here. The if() immediately above your comment > uses ch_mask to check the already-prepared state. I was referring to the 1. above, you read the prepare status without checking for ch_mask first. >>> +        /* Wait for completion on port ready */ >>> +        port_ready = &s_rt->slave->port_ready[p_rt->num]; >>> +        wait_for_completion_timeout(port_ready, msecs_to_jiffies(ch_prep_timeout)); >> >> I understand the code is the same as before but would there be any merit in checking the timeout before starting a read? If the device is already in the weeds, doing another read adds even more time before reporting an error. >> > Do you mean save the system time when the DPN_PREPARE was written to > that peripheral and then check here whether the timeout period has > already elapsed? I meant testing the return value of wait_for_completion_timeout(). If you already timed out at this point with a return value of zero, there's no point in checking the status any more, the system is in the weeds. > If that's what you mean, I don't see much advantage in that. If the > hardware is working correctly, this will be detected by the read above > that checks if the peripheral has already prepared. If it has we skip > the wait_for_completion_timeout(). > > If the peripheral is "in the weeds", so that its prepare time has > already passed and it still isn't ready, we're no longer in a state > where we care about minimizing audio startup time because the hardware > is now broken. So it's probably not worth complicating the code to > take a few milliseconds off that case. I agree it's no longer about minimizing the start time but rather providing an error faster, without waiting for a second timeout on read. >>> +        val = sdw_read_no_pm(s_rt->slave, SDW_DPN_PREPARESTATUS(p_rt->num)); >>> +        if ((val < 0) || (val & p_rt->ch_mask)) { >>> +            ret = (val < 0) ? val : -ETIMEDOUT; >>> +            goto err; >>> +        } >>> +    } >> T >> >