linux-kernel - Re: TDM bus support in Linux Kernel [PATCH]

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Message-ID: <2570275.zfck7HrlM6@linux-5eaq.site>
Date:	Wed, 30 Jan 2013 14:43:29 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Kurachkin Michail <Michail.Kurachkin@...mwad.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kuten Ivan <Ivan.Kuten@...mwad.com>,
	"benavi@...vell.com" <benavi@...vell.com>,
	Palstsiuk Viktar <Viktar.Palstsiuk@...mwad.com>
Subject: Re: TDM bus support in Linux Kernel [PATCH]

On Wednesday 30 January 2013 12:37:25 Kurachkin Michail wrote:
> Hi Greg,
> 
> I followed your recommendations and created a diff using Linux 3.8-rc5 sources. Please review it and give your comments.
> 
Part #5

+/**
+ * Reset SLIC
+ */
+static int slic_reset(struct si3226x_slic *slic)
+{
+	unsigned long timeout;
+
+	gpio_set_value(slic->reset_gpio, 0);
+
+	timeout = jiffies + MSEC(RESET_SLIC_PERIOD);
+
+	while(!(time_after(jiffies, timeout)))
+		schedule();

Ouch. We have a delay primitive.

+
+	gpio_set_value(slic->reset_gpio, 1);
+
+	return 0;
+}

+/**
+ * Receive voice data block from TDM voice channel controller.
+ * @param ch - voice channel attendant to transmit data in TDM frame
+ * @param data - pointer to read data received by DMA.
+                 Length data for read equal to value returned by get_tdm_voice_block_size()
+ *
+ * Context: can sleep
+ * @return 0 on success; negative errno on failure
+ */
+static int kirkwood_recv(struct tdm_voice_channel *ch, u8 *data)
+{
+	struct kirkwood_tdm_voice *onchip_ch = ch->private_data;
+
+	wait_event_interruptible(ch->rx_queue,
+	                         get_rx_latency(onchip_ch) > 1);

If you are waiting interruptably, you need to be able to handle an interruption.

+
+	memcpy(data, onchip_ch->rx_buf[atomic_read(&onchip_ch->read_rx_buf_num)],
+	       ch->buffer_len);
+
+	atomic_set(&onchip_ch->read_rx_buf_num,
+	           inc_next_dma_buf_num(atomic_read(&onchip_ch->read_rx_buf_num)));
+
+	return 0;
+}
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