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50 lines
1.9 KiB
Diff
50 lines
1.9 KiB
Diff
From afb1d05657278c16cca2a9fa96ef9a6c7170d07d Mon Sep 17 00:00:00 2001
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From: Mariusz Bialonczyk <manio@skyboo.net>
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Date: Thu, 21 Mar 2019 11:52:55 +0100
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Subject: [PATCH 501/515] w1: fix the resume command API
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commit 62909da8aca048ecf9fbd7e484e5100608f40a63 upstream.
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>From the DS2408 datasheet [1]:
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"Resume Command function checks the status of the RC flag and, if it is set,
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directly transfers control to the control functions, similar to a Skip ROM
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command. The only way to set the RC flag is through successfully executing
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the Match ROM, Search ROM, Conditional Search ROM, or Overdrive-Match ROM
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command"
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The function currently works perfectly fine in a multidrop bus, but when we
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have only a single slave connected, then only a Skip ROM is used and Match
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ROM is not called at all. This is leading to problems e.g. with single one
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DS2408 connected, as the Resume Command is not working properly and the
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device is responding with failing results after the Resume Command.
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This commit is fixing this by using a Skip ROM instead in those cases.
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The bandwidth / performance advantage is exactly the same.
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Refs:
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[1] https://datasheets.maximintegrated.com/en/ds/DS2408.pdf
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Signed-off-by: Mariusz Bialonczyk <manio@skyboo.net>
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Reviewed-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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drivers/w1/w1_io.c | 3 +--
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1 file changed, 1 insertion(+), 2 deletions(-)
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diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
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index 0364d3329c52..3516ce6718d9 100644
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--- a/drivers/w1/w1_io.c
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+++ b/drivers/w1/w1_io.c
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@@ -432,8 +432,7 @@ int w1_reset_resume_command(struct w1_master *dev)
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if (w1_reset_bus(dev))
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return -1;
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- /* This will make only the last matched slave perform a skip ROM. */
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- w1_write_8(dev, W1_RESUME_CMD);
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+ w1_write_8(dev, dev->slave_count > 1 ? W1_RESUME_CMD : W1_SKIP_ROM);
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return 0;
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}
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EXPORT_SYMBOL_GPL(w1_reset_resume_command);
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--
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2.19.1
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