linux-kernel - Re: [PATCH V5 6/7] i2c: tegra: fix PIO rx/tx residual transfer check

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Message-ID: <42ce2523-dab9-0cdf-e8ff-42631dd161b7@gmail.com>
Date:   Wed, 12 Jun 2019 17:30:15 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Bitan Biswas <bbiswas@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <treding@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, Peter Rosin <peda@...ntia.se>,
        Wolfram Sang <wsa@...-dreams.de>
Cc:     Shardar Mohammed <smohammed@...dia.com>,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        Mantravadi Karthik <mkarthik@...dia.com>
Subject: Re: [PATCH V5 6/7] i2c: tegra: fix PIO rx/tx residual transfer check

11.06.2019 13:51, Bitan Biswas пишет:
> Fix expression for residual bytes(less than word) transfer
> in I2C PIO mode RX/TX.
> 
> Signed-off-by: Bitan Biswas <bbiswas@...dia.com>
> ---

[snip]

>  		/*
> -		 * Update state before writing to FIFO.  If this casues us
> +		 * Update state before writing to FIFO.  If this causes us
>  		 * to finish writing all bytes (AKA buf_remaining goes to 0) we
>  		 * have a potential for an interrupt (PACKET_XFER_COMPLETE is
> -		 * not maskable).  We need to make sure that the isr sees
> -		 * buf_remaining as 0 and doesn't call us back re-entrantly.
> +		 * not maskable).
>  		 */
>  		buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;

Looks like the comment could be removed altogether because it doesn't
make sense since interrupt handler is under xfer_lock which is kept
locked during of tegra_i2c_xfer_msg().

Moreover the comment says that "PACKET_XFER_COMPLETE is not maskable",
but then what I2C_INT_PACKET_XFER_COMPLETE masking does?