* [PATCH] cpm: rounding of brg clockdivider
@ 2007-10-02 7:24 Esben Haabendal
2007-10-02 15:46 ` Scott Wood
0 siblings, 1 reply; 2+ messages in thread
From: Esben Haabendal @ 2007-10-02 7:24 UTC (permalink / raw)
To: Scott Wood, LinuxPPC-dev
Do rounding of brg clockdivider instead of truncate to get more precise baudrates
Something similar might be needed for cpm_fastbrg...
---
commit 52d631eb8f64cef794d6aa66494e253cf268894e
tree 956149a0eb5beb9afb280f4593615929eab7b779
parent 300070dd6b5e71af0c6fbecd32388905dbdd3ea5
author Esben Haabendal <eha@doredevelopment.dk> Wed, 19 Sep 2007 13:18:59 +0200
committer Esben Haabendal <esben@esben.doredevelopment.dk> Wed, 19 Sep 2007 13:18:59 +0200
arch/powerpc/sysdev/cpm2_common.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/arch/powerpc/sysdev/cpm2_common.c b/arch/powerpc/sysdev/cpm2_common.c
index 9058da2..a2c8157 100644
--- a/arch/powerpc/sysdev/cpm2_common.c
+++ b/arch/powerpc/sysdev/cpm2_common.c
@@ -102,7 +102,9 @@ cpm_setbrg(uint brg, uint rate)
brg -= 4;
}
bp += brg;
- out_be32(bp, (((BRG_UART_CLK / rate) - 1) << 1) | CPM_BRG_EN);
+ /* Set the BRG clock divider to get the best match to the requested
+ * baudrate (rounding required) */
+ out_be32(bp, ((((((BRG_UART_CLK*2)/rate)+1)/2)-1) << 1) | CPM_BRG_EN);
cpm2_unmap(bp);
}
!-------------------------------------------------------------flip-
--
Esben Haabendal
Embedded Software Consultant
Doré Development ApS
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] cpm: rounding of brg clockdivider
2007-10-02 7:24 [PATCH] cpm: rounding of brg clockdivider Esben Haabendal
@ 2007-10-02 15:46 ` Scott Wood
0 siblings, 0 replies; 2+ messages in thread
From: Scott Wood @ 2007-10-02 15:46 UTC (permalink / raw)
To: Esben Haabendal; +Cc: LinuxPPC-dev
Esben Haabendal wrote:
> Do rounding of brg clockdivider instead of truncate to get more precise baudrates
IIRC, the truncated divider produced better results with serial on
mpc8272ads...
-Scott
^ permalink raw reply [flat|nested] 2+ messages in thread
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2007-10-02 15:46 ` Scott Wood
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