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From:   Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Subject: Re: [PATCH v9 2/3] spi: Add Renesas R-Car Gen3 RPC-IF SPI controller
 driver
To:     masonccyang@mxic.com.tw
Cc:     bbrezillon@kernel.org, broonie@kernel.org,
        devicetree@vger.kernel.org,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Simon Horman <horms@verge.net.au>, juliensu@mxic.com.tw,
        lee.jones@linaro.org, linux-kernel@vger.kernel.org,
        linux-renesas-soc@vger.kernel.org, linux-spi@vger.kernel.org,
        marek.vasut@gmail.com, mark.rutland@arm.com, robh+dt@kernel.org,
        zhengxunli@mxic.com.tw
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 <OFAEA16021.C7F7B095-ON482583D1.0031A13D-482583D1.00335085@mxic.com.tw>
Organization: Cogent Embedded
Message-ID: <7467d695-8922-16b2-03d4-fb4bbdda125a@cogentembedded.com>
Date:   Thu, 4 Apr 2019 21:56:19 +0300
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Hello!

On 04/03/2019 12:20 PM, masonccyang@mxic.com.tw wrote:

>> >> > +static void rpc_spi_mem_set_prep_op_cfg(struct spi_device *spi,
>> >> > +               const struct spi_mem_op *op,
>> >> > +               u64 *offs, size_t *len)
>> >> > +{
>> >> > +   struct rpc_spi *rpc = spi_controller_get_devdata(spi->controller);
>> >> > +
>> >> > +   rpc->cmd = RPC_SMCMR_CMD(op->cmd.opcode);
>> >> > +   rpc->smenr = RPC_SMENR_CDE |
>> >> > +           RPC_SMENR_CDB(ilog2(op->cmd.buswidth));
>> >> > +   rpc->totalxferlen = 1;
>> >> > +   rpc->xfer_dir = SPI_MEM_NO_DATA;
>> >> > +   rpc->xferlen = 0;
>> >> > +   rpc->addr = 0;
>> >> > +
>> >> > +   if (op->addr.nbytes) {
>> >> > +      rpc->smenr |= RPC_SMENR_ADB(ilog2(op->addr.buswidth));
>> >> > +      if (op->addr.nbytes == 4)
>> >> > +         rpc->smenr |= RPC_SMENR_ADE(0xf);
>> >> > +      else
>> >> > +         rpc->smenr |= RPC_SMENR_ADE(0x7);
>> >> > +
>> >> > +      if (offs && len)
>> >> > +         rpc->addr = *offs;
>> >> > +      else
>> >> > +         rpc->addr = op->addr.val;
>> >> > +      rpc->totalxferlen += op->addr.nbytes;
>> >> > +   }
>> >> > +
>> >> > +   if (op->dummy.nbytes) {
>> >> > +      rpc->smenr |= RPC_SMENR_DME;
>> >> > +      rpc->dummy = RPC_SMDMCR_DMCYC(op->dummy.nbytes);
>> >>
>> >>    So you haven't fixed this bug? I repeat, the driver doesn't work right
>> >> w/o this fixed!
>> >
>> > Do you mean
>> >
>> > rpc->dummy = RPC_SMDMCR_DMCYC(op->dummy.nbytes) * 8;   ?
>>
>>    Yes. Or some other code that amounts to it.

   Oops, I wasn't attentive enough, I was proposing:

	rpc->dummy = RPC_SMDMCR_DMCYC(op->dummy.nbytes * 8);

> why not setting "op->dummy.nbytes = 7" from spi-nor.c protocol layer ?

   We want 8 dummy clocks, not 8 dummy bytes. And if you'd looked into
spi_nor_read_sfdp(), you'd have seen that it requests 8 dummy clocks already.

> driver may check device ID or something else to setup op->dummy.nbytes.

   The RDSFDP command is not chip specific.

> I think it is not a good idea to *8 in spi host driver.

>> > What is your flash part number?
>>
>>    Spansion/Cypress S25FS512S. The datasheet says there must be 8 dummy cycles
>> for the RSFDP command...
>>
>> > The problem you found is in 1 bit or 4 bits width ?
>>
>>    1-bit, I think.
>>
>> >>
>> >> [...]
>> >> > +static ssize_t rpc_spi_mem_dirmap_read(struct spi_mem_dirmap_desc *desc,
>> >> > +                   u64 offs, size_t len, void *buf)
>> >> > +{
>> >> > +   struct rpc_spi *rpc =
>> >> > +         spi_controller_get_devdata(desc->mem->spi->controller);
>> >> > +   int ret;
>> >> > +
>> >> > +   if (offs + desc->info.offset + len > U32_MAX)
>> >> > +      return -EINVAL;
>> >> > +
>> >> > +   if (len > 0x4000000)
>> >> > +      len = 0x4000000;
>> >>
>> >>    Ugh...
>> >
>> > by mtd->size ?
>>
>>   That'd be better, yes.
>>
> 
> Oops, it seems hard to get mtd->size info. from spi_mem_dirmap,

   It's in desc->info.length, no?

> I would like to keep 0x4000000.

   I'm seeing Boris in the CC's... Boris, is it legitimate to limit
a single dirmap read by the memory "window" size? Or should we try to 
serve any valid transfer length?

>> >> > +
>> >> > +   ret = rpc_spi_set_freq(rpc, desc->mem->spi->max_speed_hz);
>> >> > +   if (ret)
>> >> > +      return ret;
>> >> > +
>> >> > +   rpc_spi_mem_set_prep_op_cfg(desc->mem->spi,
>> >> > +                &desc->info.op_tmpl, &offs, &len);
>> >> > +
>> >> > +   regmap_update_bits(rpc->regmap, RPC_CMNCR, RPC_CMNCR_MD, 0);
>> >> > +   regmap_write(rpc->regmap, RPC_DRCR, RPC_DRCR_RBURST(32) |
>> >> > +           RPC_DRCR_RBE);
>> >> > +
>> >> > +   regmap_write(rpc->regmap, RPC_DRCMR, rpc->cmd);
>> >> > +   regmap_write(rpc->regmap, RPC_DREAR, RPC_DREAR_EAC(1));
>> >>
>> >>    So you're not even trying to support flashes larger than the
>> read dirmap?
>> >> Now I don't think it's acceptable (and I have rewritten this code
>> internally).
>> >
>> > what about the size comes form mtd->size ?
>>
>>    I'm not talking about size here; we should use the full address.
>> I'm attaching
>> my patch...
> 
> okay,got it!
> what about just
> -      regmap_write(rpc->mfd->regmap, RPC_DREAR, RPC_DREAR_EAC(1));
> +      regmap_write(rpc->mfd->regmap, RPC_DREAR,
> +                   RPC_DREAR_EAV(offs >> 25) | RPC_DREAR_EAC(1));
> 
> because only > 64MByte size make RPC_DREAR_EAV() work.

   Boris, what's your opinion on this?
   Note that for the write dirmap we have just 256-byte buffer (reusing
the read cache). Is it legitimate to limit the served length to 256 bytes?

> thanks & best regards,
> Mason

MBR, Sergei