From: Dirk Behme <dirk.behme@de.bosch.com>
To: xen-devel@lists.xenproject.org,
Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr.tyshchenko@globallogic.com>,
Iurii Konovalenko <iurii.konovalenko@globallogic.com>,
Dirk Behme <dirk.behme@de.bosch.com>
Subject: [PATCH 3/3] xen/arm: drivers: scif: Add clock auto detection
Date: Tue, 21 Jun 2016 11:15:28 +0200 [thread overview]
Message-ID: <1466500528-8411-3-git-send-email-dirk.behme@de.bosch.com> (raw)
In-Reply-To: <1466500528-8411-1-git-send-email-dirk.behme@de.bosch.com>
Besides the 14MHz external clock, the SCIF might be clocked by an
internal 66MHz clock. Detect this clock based on the SCIF_DL register
being 0 (internal clock) or != 0 (external clock).
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
---
xen/drivers/char/scif-uart.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/xen/drivers/char/scif-uart.c b/xen/drivers/char/scif-uart.c
index bc157fe..678f46b 100644
--- a/xen/drivers/char/scif-uart.c
+++ b/xen/drivers/char/scif-uart.c
@@ -107,8 +107,19 @@ static void __init scif_uart_init_preirq(struct serial_port *port)
scif_readw(uart, SCIF_SCLSR);
scif_writew(uart, SCIF_SCLSR, 0);
- /* Select Baud rate generator output as a clock source */
- scif_writew(uart, SCIF_SCSCR, SCSCR_CKE10);
+ /*
+ * Select Baud rate generator output as a clock source
+ * The clock source can be an internal or external clock.
+ * Depending on this the DL register is either 0 or contains
+ * the divisor. I.e. we can use this to detect the clock
+ * source and based on this can configure the CKE[1:0] bits
+ * of the SCSCR register.
+ */
+ if ( scif_readw(uart, SCIF_DL) )
+ scif_writew(uart, SCIF_SCSCR, SCSCR_CKE10); /* External clk */
+ else
+ scif_writew(uart, SCIF_SCSCR, SCSCR_CKE00); /* Internal clk */
+
/* Setup protocol format and Baud rate, select Asynchronous mode */
val = 0;
--
2.8.0
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next prev parent reply other threads:[~2016-06-21 9:16 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-21 9:15 [PATCH 1/3] xen/arm: drivers: scif: Remove dead code Dirk Behme
2016-06-21 9:15 ` [PATCH 2/3] xen/arm: drivers: scif: Remove unused variables Dirk Behme
2016-06-21 12:17 ` Julien Grall
2016-06-21 9:15 ` Dirk Behme [this message]
2016-06-21 12:20 ` [PATCH 3/3] xen/arm: drivers: scif: Add clock auto detection Julien Grall
2016-06-21 12:30 ` Dirk Behme
2016-06-21 12:33 ` Julien Grall
2016-06-21 10:16 ` [PATCH 1/3] xen/arm: drivers: scif: Remove dead code Oleksandr Tyshchenko
2016-06-21 12:15 ` Julien Grall
2016-06-21 12:54 ` Oleksandr Tyshchenko
2016-06-21 13:01 ` Dirk Behme
2016-06-21 13:22 ` Oleksandr Tyshchenko
2016-06-21 13:07 ` Julien Grall
2016-06-21 13:11 ` Oleksandr Tyshchenko
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