From: Nishanth Menon <nm@ti.com>
To: linux-omap <linux-omap@vger.kernel.org>
Cc: Deepak K <deepak.k@ti.com>, Govindraj R <govindraj.raja@ti.com>,
Kevin Hilman <khilman@deeprootsystems.com>,
Tero Kristo <tero.kristo@nokia.com>, Nishanth Menon <nm@ti.com>
Subject: [PM][PATCH 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access
Date: Thu, 8 Apr 2010 12:54:07 -0500 [thread overview]
Message-ID: <1270749249-14041-3-git-send-email-nm@ti.com> (raw)
In-Reply-To: <1270749249-14041-2-git-send-email-nm@ti.com>
From: Deepak K <deepak.k@ti.com>
Original patch:
http://git.omapzoom.org/?p=kernel/omap.git;a=commitdiff;h=42d4a342c009bd9727c100abc8a4bc3063c22f0c
Errata i202 (OMAP3430 - 1.12, OMAP3630 - 1.6):
UART module MDR1 register access can cause a dummy underrun
condition which could result in a freeze in the case of IrDA
communication or if used as UART, corrupted data.
Workaround is as follows for everytime MDR1 register is changed:
* setup all required UART registers
* setup MDR1.MODE_SELECT bit field
* Wait 5 L4 clk cycles + 5 UART functional clock cycles
* Clear the Tx and RX fifo using FCR register
Note: The following step is not done as I am assuming it is not
needed due to reconfiguration being done and there is no halted
operation perse.
* Read if required, the RESUME register to resume halted operation
Cc: Govindraj R <govindraj.raja@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Deepak K <deepak.k@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
---
Note: original patch was done for android kernel, ported and sanity
tested
arch/arm/mach-omap2/serial.c | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
index 86d3b47..144033f 100644
--- a/arch/arm/mach-omap2/serial.c
+++ b/arch/arm/mach-omap2/serial.c
@@ -223,6 +223,19 @@ static void omap_uart_restore_context(struct omap_uart_state *uart)
uart->context_valid = 0;
serial_write_reg(p, UART_OMAP_MDR1, 0x7);
+ /*
+ * Work Around for Errata i202 (3430 - 1.12, 3630 - 1.6)
+ * The access to uart register after MDR1 Access
+ * causes UART to corrupt data.
+ *
+ * Need a delay =
+ * 5 L4 clock cycles + 5 UART functional clock cycle (@48MHz = ~0.2uS)
+ * give 10 times as much
+ */
+ udelay(2);
+ /* TX and RX FIFO Clear; FIFO dis */
+ serial_write_reg(p, UART_FCR, 0xA6);
+
serial_write_reg(p, UART_LCR, 0xBF); /* Config B mode */
efr = serial_read_reg(p, UART_EFR);
serial_write_reg(p, UART_EFR, UART_EFR_ECB);
@@ -235,7 +248,6 @@ static void omap_uart_restore_context(struct omap_uart_state *uart)
serial_write_reg(p, UART_IER, uart->ier);
serial_write_reg(p, UART_LCR, 0x80);
serial_write_reg(p, UART_MCR, uart->mcr);
- serial_write_reg(p, UART_FCR, 0xA1);
serial_write_reg(p, UART_LCR, 0xBF); /* Config B mode */
serial_write_reg(p, UART_EFR, efr);
serial_write_reg(p, UART_LCR, UART_LCR_WLEN8);
@@ -243,6 +255,10 @@ static void omap_uart_restore_context(struct omap_uart_state *uart)
serial_write_reg(p, UART_OMAP_WER, uart->wer);
serial_write_reg(p, UART_OMAP_SYSC, uart->sysc);
serial_write_reg(p, UART_OMAP_MDR1, 0x00); /* UART 16x mode */
+ /* Errata: i202 */
+ udelay(2);
+ /* TX and RX FIFO Clear; FIFO en */
+ serial_write_reg(p, UART_FCR, 0xA7);
}
#else
static inline void omap_uart_save_context(struct omap_uart_state *uart) {}
--
1.6.3.3
next prev parent reply other threads:[~2010-04-08 17:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-08 17:54 [PM][PATCH 0/4] OMAP3: Serial Misc fixes Nishanth Menon
2010-04-08 17:54 ` [PM][PATCH 1/4] OMAP3: Serial: Add context save and restore for mcr Nishanth Menon
2010-04-08 17:54 ` Nishanth Menon [this message]
2010-04-08 17:54 ` [PM][PATCH 3/4] OMAP3: Serial: remove initialization sparse warnings Nishanth Menon
2010-04-08 17:54 ` [PM][PATCH 4/4] OMAP3: Serial: kill dev_attr_sleep_timeout sparse warn Nishanth Menon
2010-05-05 23:57 ` Kevin Hilman
2010-04-09 17:00 ` [PM][PATCH 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access Nishanth Menon
2010-04-09 17:06 ` Kattungal, Deepak
2010-04-09 17:21 ` Nishanth Menon
2010-05-05 23:49 ` [PM][PATCH 1/4] OMAP3: Serial: Add context save and restore for mcr Kevin Hilman
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