linux-kernel - Re: [PATCH v1 1/1] mtd: mtk-nor: set controller's address width according to nor flash

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Message-ID: <3cf1c63e-c56f-2f07-9d16-7ec346758dfa@wedev4u.fr>
Date:   Thu, 13 Apr 2017 10:24:58 +0200
From:   Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>
To:     Guochun Mao <guochun.mao@...iatek.com>
Cc:     Cyrille Pitchen <cyrille.pitchen@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, Richard Weinberger <richard@....at>,
        Russell King <linux@...linux.org.uk>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        linux-mtd@...ts.infradead.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-mediatek@...ts.infradead.org,
        David Woodhouse <dwmw2@...radead.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 1/1] mtd: mtk-nor: set controller's address width
 according to nor flash

Hi Guochun,

Le 13/04/2017 à 04:40, Guochun Mao a écrit :
> Hi Cyrille,
> 
> On Wed, 2017-04-12 at 22:57 +0200, Cyrille Pitchen wrote:
>> Hi Guochun,
>>
>> Le 05/04/2017 à 10:37, Guochun Mao a écrit :
>>> When nor's size larger than 16MByte, nor's address width maybe
>>> set to 3 or 4, and controller should change address width according
>>> to nor's setting.
>>>
>>> Signed-off-by: Guochun Mao <guochun.mao@...iatek.com>st

Acked-by: Cyrille Pitchen <cyrille.pitchen@...el.com>

>>> ---
>>>  drivers/mtd/spi-nor/mtk-quadspi.c |   27 +++++++++++++++++++++++++++
>>>  1 file changed, 27 insertions(+)
>>>
>>> diff --git a/drivers/mtd/spi-nor/mtk-quadspi.c b/drivers/mtd/spi-nor/mtk-quadspi.c
>>> index e661877..b637770 100644
>>> --- a/drivers/mtd/spi-nor/mtk-quadspi.c
>>> +++ b/drivers/mtd/spi-nor/mtk-quadspi.c
>>> @@ -104,6 +104,8 @@
>>>  #define MTK_NOR_MAX_RX_TX_SHIFT		6
>>>  /* can shift up to 56 bits (7 bytes) transfer by MTK_NOR_PRG_CMD */
>>>  #define MTK_NOR_MAX_SHIFT		7
>>> +/* nor controller 4-byte address mode enable bit */
>>> +#define MTK_NOR_4B_ADDR_EN		BIT(4)
>>>  
>>>  /* Helpers for accessing the program data / shift data registers */
>>>  #define MTK_NOR_PRG_REG(n)		(MTK_NOR_PRGDATA0_REG + 4 * (n))
>>> @@ -230,10 +232,35 @@ static int mt8173_nor_write_buffer_disable(struct mt8173_nor *mt8173_nor)
>>>  				  10000);
>>>  }
>>>  
>>> +static void mt8173_nor_set_addr_width(struct mt8173_nor *mt8173_nor)
>>> +{
>>> +	u8 val;
>>> +	struct spi_nor *nor = &mt8173_nor->nor;
>>> +
>>> +	val = readb(mt8173_nor->base + MTK_NOR_DUAL_REG);
>>> +
>>> +	switch (nor->addr_width) {
>>> +	case 3:
>>> +		val &= ~MTK_NOR_4B_ADDR_EN;
>>> +		break;
>>> +	case 4:
>>> +		val |= MTK_NOR_4B_ADDR_EN;
>>> +		break;
>>> +	default:
>>> +		dev_warn(mt8173_nor->dev, "Unexpected address width %u.\n",
>>> +			 nor->addr_width);
>>> +		break;
>>> +	}
>>> +
>>> +	writeb(val, mt8173_nor->base + MTK_NOR_DUAL_REG);
>>> +}
>>> +
>>>  static void mt8173_nor_set_addr(struct mt8173_nor *mt8173_nor, u32 addr)
>>>  {
>>>  	int i;
>>>  
>>> +	mt8173_nor_set_addr_width(mt8173_nor);
>>> +
>>>  	for (i = 0; i < 3; i++) {
>>
>> Should it be 'i < nor->addr_width' instead of 'i < 3' ?
>> Does it work when accessing data after 128Mbit ?
> 
> Yes, it can work.
> 
> Let's see the whole function,
> 
> static void mt8173_nor_set_addr(struct mt8173_nor *mt8173_nor, u32 addr)
> {
>         int i;
> 
>         mt8173_nor_set_addr_width(mt8173_nor);
> 
>         for (i = 0; i < 3; i++) {
>                 writeb(addr & 0xff, mt8173_nor->base + MTK_NOR_RADR0_REG
> + i * 4);
>                 addr >>= 8;
>         }
>         /* Last register is non-contiguous */
>         writeb(addr & 0xff, mt8173_nor->base + MTK_NOR_RADR3_REG);
> }
> 
> The nor controller has 4 registers for address.
> This '3' indicates the number of contiguous address' registers
> base + MTK_NOR_RADR0_REG(0x10)
> base + MTK_NOR_RADR1_REG(0x14)
> base + MTK_NOR_RADR2_REG(0x18),
> but the last address register is non-contiguous,
> it's base + MTK_NOR_RADR3_REG(0xc8)
> 
> mt8173_nor_set_addr will set addr into these 4 registers by Byte.
> The bit MTK_NOR_4B_ADDR_EN will decide whether 3-byte(0x10,0x14,0x18)
> or 4-byte(0x10,0x14,x018,0xc8) been sent to nor device.
> and, it can access data after 128Mbit when sent 4-byte address.

Indeed, you're right. Sorry for the noise!

> 
> Best regards,
> 
> Guochun
> 
>>
>> Best regards,
>>
>> Cyrille
>>
>>>  		writeb(addr & 0xff, mt8173_nor->base + MTK_NOR_RADR0_REG + i * 4);
>>>  		addr >>= 8;
>>>
>>
> 
> 
>