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Date:   Fri, 21 May 2021 08:51:16 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Zheyu Ma <zheyuma97@gmail.com>
Cc:     cernekee@gmail.com, jirislaby@kernel.org,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] serial: rp2: use 'request_firmware' instead of
 'request_firmware_nowait'
Message-ID: <YKdYZF8zDGl0hxeX@kroah.com>
References: <1621577323-1541-1-git-send-email-zheyuma97@gmail.com>
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On Fri, May 21, 2021 at 06:08:43AM +0000, Zheyu Ma wrote:
> In 'rp2_probe', the driver registers 'rp2_uart_interrupt' then calls
> 'rp2_fw_cb' through 'request_firmware_nowait'. In 'rp2_fw_cb', if the
> firmware don't exists, function just return without initializing ports
> of 'rp2_card'. But now the interrupt handler function has been
> registered, and when an interrupt comes, 'rp2_uart_interrupt' may access
> those ports then causing NULL pointer dereference or other bugs.
> 
> Because the driver does some initialization work in 'rp2_fw_cb', in
> order to make the driver ready to handle interrupts, 'request_firmware'
> should be used instead of asynchronous 'request_firmware_nowait'.

You just now slowed down the probe function.  Are you _sure_ this is ok?

Do you have this hardware to test this?  If so, what is the init time
before and after this change?

thanks,

greg k-h