linux-kernel - Re: [PATCH v2] soundwire: bus: Don't filter slave alerts

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Message-ID: <ZFilyckgWJlHiBiU@matsya>
Date:   Mon, 8 May 2023 13:03:29 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     yung-chuan.liao@...ux.intel.com,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH v2] soundwire: bus: Don't filter slave alerts

On 18-04-23, 15:06, Charles Keepax wrote:
> It makes sense to have only a single point responsible for ensuring
> that all currently pending IRQs are handled. The current code in
> sdw_handle_slave_alerts confusingly splits this process in two.  This
> code will loop until the asserted IRQs are cleared but it will only
> handle IRQs that were already asserted when it was called. This
> means the caller must also loop (either manually, or through its IRQ
> mechanism) until the IRQs are all handled. It makes sense to either do
> all the looping in sdw_handle_slave_alerts or do no looping there and
> let the host controller repeatedly call it until things are handled.
> 
> There are realistically two sensible host controllers, those that
> will generate an IRQ when the alert status changes and those
> that will generate an IRQ continuously whilst the alert status
> is high. The current code will work fine for the second of those
> systems but not the first with out additional looping in the host
> controller.  Removing the code that filters out new IRQs whilst
> the handler is running enables both types of host controller to be
> supported and simplifies the code. The code will still only loop up to
> SDW_READ_INTR_CLEAR_RETRY times, so it shouldn't be possible for it to
> get completely stuck handling IRQs forever, and if you are generating
> IRQs faster than you can handle them you likely have bigger problems
> anyway.
> 
> This fixes an issue on the Cadence SoundWire IP, which only generates
> IRQs on an alert status change, where an alert which arrives whilst
> another alert is being handled will never be handled and will block
> all future alerts from being handled.

Applied, thanks

-- 
~Vinod