[PATCH v7 2/2] mtd: fsl-quadspi: fix init AHB read in fsl_qspi_nor_setup()

[Frieder Schrempf]

Hi Yogesh,

On 22.03.2018 11:37, Yogesh Narayan Gaur wrote:
> Hi Frieder,
> 
>> -----Original Message-----
>> From: linux-mtd [mailto:linux-mtd-bounces at lists.infradead.org] On Behalf Of
>> Frieder Schrempf
>> Sent: Thursday, March 22, 2018 2:49 PM
>> To: Yogesh Narayan Gaur <yogeshnarayan.gaur at nxp.com>; linux-
>> mtd at lists.infradead.org
>> Cc: boris.brezillon at free-electrons.com; marek.vasut at gmail.com; Prabhakar
>> Kushwaha <prabhakar.kushwaha at nxp.com>; Suresh Gupta
>> <suresh.gupta at nxp.com>; cyrille.pitchen at wedev4u.fr; Han Xu
>> <han.xu at nxp.com>; computersforpeace at gmail.com; festevam at gmail.com
>> Subject: Re: [PATCH v7 2/2] mtd: fsl-quadspi: fix init AHB read in
>> fsl_qspi_nor_setup()
>>
>> Hi Yogesh,
>>
>> On 21.03.2018 12:26, Yogesh Gaur wrote:
>>> Move AHB read initialize in fsl_qspi_nor_setup().
>>>
>>> In file spi-nor.c, func spi_nor_scan() calls nor->read() thru
>>> spi_nor_read_sfdp() API.
>>>
>>> Presently, fsl_qspi_init_ahb_read() called from fsl_qspi_nor_setup_last().
>>> Func fsl_qspi_probe() calls spi_nor_scan() first and then calls
>>> fsl_qspi_nor_setup_last().
>>>
>>> When nor->read() being called from inside spi_nor_read_sfdp(), QSPI
>>> cntlr AHB mode initialization is not yet done results in data read error.
>>>
>>> Initialize AHB read inside fsl_qspi_nor_setup().
>>>
>>> Signed-off-by: Yogesh Gaur <yogeshnarayan.gaur at nxp.com>
>>> ---
>>> Changes for v7:
>>> - None
>>> Changes for v6:
>>> - None
>>> Changes for v5:
>>> - None
>>> Changes for v4:
>>> - None
>>> Changes for v3:
>>> - None
>>> Changes for v2:
>>> - None
>>>
>>>    drivers/mtd/spi-nor/fsl-quadspi.c | 6 +++---
>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c
>>> b/drivers/mtd/spi-nor/fsl-quadspi.c
>>> index 64b8bb3..424094a 100644
>>> --- a/drivers/mtd/spi-nor/fsl-quadspi.c
>>> +++ b/drivers/mtd/spi-nor/fsl-quadspi.c
>>> @@ -820,6 +820,9 @@ static int fsl_qspi_nor_setup(struct fsl_qspi *q)
>>>    	/* enable the interrupt */
>>>    	qspi_writel(q, QUADSPI_RSER_TFIE, q->iobase + QUADSPI_RSER);
>>>
>>> +	/* Init for AHB read */
>>> +	fsl_qspi_init_ahb_read(q);
>>
>> Maybe I missed something, but it seems if you move
>> fsl_qspi_init_ahb_read() here and fsl_qspi_read() is used before
>> fsl_qspi_nor_setup_last() is called, then the read command is triggered with an
>> uninitialized LUT entry (SEQID_LUT2_AHBREAD).
>>
> For every call to fsl_qspi_read(), I am preparing the LUT before doing actual read so LUT entry for SEQID_LUT2_AHBREAD is never be uninitialized.

Ok, I missed that. Thank you for clarifying this.

Thanks,

Frieder

> 
> Rationale behind moving fsl_qspi_init_ahb_read() from fsl_qspi_nor_setup_last() to fsl_qspi_nor_setup() is to initialize registers which are required for AHB read operation like setting of values in QUADSPI_BUF3CR, QUADSPI_BFGENCR etc registers as fsl_qspi_read() is called, before call to fsl_qspi_nor_setup_last(), through spi_nor_read_sfdp().
> 
> --
> Thanks
> Yogesh Gaur
> 
>> So shouldn't the LUT entry for AHB read be initialized with some default values
>> here, before spi_nor_scan() is called?
>>
>> Thanks,
>>
>> Frieder
>>
>>> +
>>>    	return 0;
>>>    }
>>>
>>> @@ -842,9 +845,6 @@ static int fsl_qspi_nor_setup_last(struct fsl_qspi *q)
>>>    	if (ret)
>>>    		return ret;
>>>
>>> -	/* Init for AHB read */
>>> -	fsl_qspi_init_ahb_read(q);
>>> -
>>>    	/* Prepare LUT for AHB read - required for read from devmem interface
>> */
>>>    	fsl_qspi_prep_ahb_read(q);
>>>
>>>
>>
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