[RFC] mn88472: reduce firmware download chunk size

Commit Message

Benjamin Larsson Feb. 19, 2015, 11:53 a.m. UTC

On 2015-02-19 11:21, Antti Seppälä wrote:
> On 19 February 2015 at 11:43, Benjamin Larsson <[e-mail]> wrote:
>> On 2015-02-19 10:13, Antti Seppälä wrote:
>>>
>>> It seems that currently the firmware download on the mn88472 is
>>> somehow wrong for my Astrometa HD-901T2.
>>>
>>> Reducing the download chunk size (mn88472_config.i2c_wr_max) to 2
>>> makes the firmware download consistently succeed.
>>>
>>
>>
>> Hi, try adding the workaround patch I sent for this.
>>
>> [PATCH 1/3] rtl28xxu: lower the rc poll time to mitigate i2c transfer errors
>>
>> I now see that it hasn't been merged. But I have been running with this
>> patch for a few months now without any major issues.
>>
>
> The patch really did improve firmware loading. Weird...
>
> Even with it I still get occasional i2c errors from r820t:
>
> [   15.874402] r820t 8-003a: r820t_write: i2c wr failed=-32 reg=0a len=1: da
> [   81.455517] r820t 8-003a: r820t_read: i2c rd failed=-32 reg=00
> len=4: 69 74 e6 df
> [   99.949702] r820t 8-003a: r820t_read: i2c rd failed=-32 reg=00
> len=4: 69 74 e6 df
>
> These errors seem to appear more often if I'm reading the signal
> strength values using e.g. femon.
>
> Br,
> -Antti
>

This patch implements a retry logic. If a transfer fails it will convert 
it to 1 byte transfers. This will not work when loading the nm88472 
firmware as everything is loaded through the 0xf6 register.

I think we might need something like this to get the Astrometa working 
reliably.

Based on usb logs from the windows driver one can see that they only 
send 1 byte at a time so they can retry all transfers. So this issue 
seems to be related to the rtl2832p bridge chip and how much i2c traffic 
is generated.

MvH
Benjamin Larsson

Patch

From 5962cf8fafdfe98138fd69beb4d0b5d2a7af5732 Mon Sep 17 00:00:00 2001
From: Benjamin Larsson <[e-mail]>
Date: Thu, 20 Nov 2014 00:50:02 +0100
Subject: [PATCH] rtl28xxu: implement i2c transfer retry logic
Cc: Linux Media Mailing List <[e-mail]>

This is needed for Astrometa hardware. Retry counts up to 6 has been
observered before the i2c transfer succeded.

Signed-off-by: Benjamin Larsson <[e-mail]>
---
 drivers/media/usb/dvb-usb-v2/rtl28xxu.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
index 4af8a61..4d321ae 100644
--- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
+++ b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
@@ -185,6 +185,8 @@  static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 	struct dvb_usb_device *d = i2c_get_adapdata(adap);
 	struct rtl28xxu_priv *priv = d->priv;
 	struct rtl28xxu_req req;
+	u8 rb_buf[2];
+	int i, retry_cnt;
 
 	/*
 	 * It is not known which are real I2C bus xfer limits, but testing
@@ -273,6 +275,33 @@  static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 			req.size = msg[0].len-1;
 			req.data = &msg[0].buf[1];
 			ret = rtl28xxu_ctrl_msg(d, &req);
+
+			/* Astrometa hardware needs a retry for some failed transfers.
+			 * Just send one byte at the time.
+			 * Retry max 10 times for each transfer.
+			 */
+			if (ret) {
+				req.size = 1;
+				req.data = rb_buf;
+
+				dev_dbg(&d->udev->dev, "%s: transfer of %d bytes failed\n", __func__, msg[0].len-1);
+				rb_buf[0] = msg[0].buf[0];
+
+				for (i=0 ; i<msg[0].len-1 ; i++) {
+					retry_cnt = 0;
+					req.value = ((msg[0].buf[0]+i) << 8) | (msg[0].addr << 1);
+					rb_buf[0] = msg[0].buf[i+1];
+
+					do {
+						dev_dbg(&d->udev->dev, "%s: byte: %d retry: %d\n", __func__, i, retry_cnt);
+						ret = rtl28xxu_ctrl_msg(d, &req);
+						retry_cnt++;
+						if (retry_cnt > 10)
+							goto err_mutex_unlock;
+
+					} while (ret);
+				}
+			}
 		} else {
 			/* method 3 - new I2C */
 			req.value = (msg[0].addr << 1);
-- 
1.9.1