linux-kernel - Re: [RFC 07/47] mtd: nand: stm_nand_bch: initialise the BCH Controller

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Date:	Wed, 30 Apr 2014 11:22:44 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	"Gupta, Pekon" <pekon@...com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kernel@...inux.com" <kernel@...inux.com>,
	"computersforpeace@...il.com" <computersforpeace@...il.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"angus.clark@...com" <angus.clark@...com>,
	"Ezequiel Garcia (ezequiel.garcia@...e-electrons.com)" 
	<ezequiel.garcia@...e-electrons.com>
Subject: Re: [RFC 07/47] mtd: nand: stm_nand_bch: initialise the BCH
 Controller

On Wed, 26 Mar 2014, Gupta, Pekon wrote:

> Hi Lee,
> 
> >From: Lee Jones [mailto:lee.jones@...aro.org]
> missing commit log :-)
> Though $subject is self-explanatory, but you can add more description about
> assumption and hardware caveats about the controller, and its use.
> 
> >
> >Signed-off-by: Lee Jones <lee.jones@...aro.org>
> >---
> > drivers/mtd/nand/stm_nand_bch.c | 56 +++++++++++++++++++++++++++++++++++++++++
> > include/linux/mtd/stm_nand.h    | 20 +++++++++++++++
> > 2 files changed, 76 insertions(+)
> >
> >diff --git a/drivers/mtd/nand/stm_nand_bch.c b/drivers/mtd/nand/stm_nand_bch.c
> >index 76a0d02..1a93f8d 100644
> >--- a/drivers/mtd/nand/stm_nand_bch.c
> >+++ b/drivers/mtd/nand/stm_nand_bch.c
> >@@ -14,6 +14,7 @@
> >
> > #include <linux/kernel.h>
> > #include <linux/module.h>
> >+#include <linux/delay.h>
> > #include <linux/io.h>
> > #include <linux/interrupt.h>
> > #include <linux/device.h>
> >@@ -102,6 +103,56 @@ static void nandi_disable_interrupts(struct nandi_controller *nandi,
> > 	writel(val, nandi->base + NANDBCH_INT_EN);
> > }
> >
> >+static void nandi_init_bch(struct nandi_controller *nandi, int emi_bank)
> >+{
> >+	dev_dbg(nandi->dev, "%s\n", __func__);
> >+
> >+	/* Initialise BCH Controller */
> >+	emiss_nandi_select(STM_NANDI_BCH);
> >+
> >+	/* Reset and disable boot-mode controller */
> >+	writel(BOOT_CFG_RESET, nandi->base + NANDBCH_BOOTBANK_CFG);
> >+	udelay(1);
> >+	writel(0x00000000, nandi->base + NANDBCH_BOOTBANK_CFG);
> 
> Why using 'udelay' ?
> Isn't there any status register which tells you that controller is reset / initialized ?
> Or may be polling on NANDBCH_BOOTBANK_CFG may itself give you status.

Documenation says:

  "The soft reset bit has to be reset to ‘0’ to de-assert the soft
   reset. The soft reset bit is expected to be asserted for at least
   one clock cycle for proper reset"

> >+
> >+	/* Reset AFM controller */
> >+	writel(CFG_RESET, nandi->base + NANDBCH_CONTROLLER_CFG);
> >+	udelay(1);
> >+	writel(0x00000000, nandi->base + NANDBCH_CONTROLLER_CFG);
> >+
> >+	/* Set EMI Bank */
> >+	writel(0x1 << emi_bank, nandi->base + NANDBCH_FLEX_MUXCTRL);
> >+
> >+	/* Reset ECC stats */
> >+	writel(0x7f0, nandi->base + NANDBCH_CONTROLLER_CFG);
> >+	udelay(1);
> >+
> "0x7f0" ?? please use Macro instead.

Sure.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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