linux-kernel - Re: [PATCH v4 01/10] spi: Add a driver for the Freescale/NXP QuadSPI controller

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Date:   Tue, 13 Nov 2018 13:56:53 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.De>
To:     Yogesh Narayan Gaur <yogeshnarayan.gaur@....com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "boris.brezillon@...tlin.com" <boris.brezillon@...tlin.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "richard@....at" <richard@....at>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        David Wolfe <david.wolfe@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Prabhakar Kushwaha <prabhakar.kushwaha@....com>,
        "Han Xu" <han.xu@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "Frieder Schrempf" <frieder.schrempf@...eet.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 01/10] spi: Add a driver for the Freescale/NXP QuadSPI
 controller

Hi Yogesh,

On 13.11.18 09:22, Yogesh Narayan Gaur wrote:
[...]
>> +
>> +static void fsl_qspi_read_ahb(struct fsl_qspi *q, const struct
>> +spi_mem_op *op) {
>> +	/*
>> +	 * We want to avoid needing to invalidate the cache by issueing
>> +	 * a reset to the AHB and Serial Flash domain, as this needs
>> +	 * time. So we change the address on each read to trigger an
>> +	 * actual read operation on the flash. The actual address for
>> +	 * the flash memory is set by programming the LUT.
>> +	 */
> As discussed previously, please go away with this hack and use AHB bus invalidation method with smaller timeout value.
> 
> I would start doing validation of this patch series from next version onward. As you have mentioned in other mail discussion about issue in the break condition for function  fsl_qspi_readl_poll_tout().

Thank you for your comments. I just sent v5 with some fixes, including 
fixed fsl_qspi_readl_poll_tout().

I also removed the hack above and I'm properly resetting the AHB domain 
now. I'm using a 1us delay just like in the old driver. In my tests the 
performance impact was very small (~2%) and it didn't get better when 
using ndelay.

Thanks,
Frieder