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Date: Fri, 4 Jan 2019 16:42:41 +0300
From: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To: masonccyang@...c.com.tw
Cc: boris.brezillon@...tlin.com, broonie@...nel.org,
Geert Uytterhoeven <geert+renesas@...der.be>,
Simon Horman <horms@...ge.net.au>, juliensu@...c.com.tw,
linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
linux-spi@...r.kernel.org, marek.vasut@...il.com,
zhengxunli@...c.com.tw
Subject: Re: [PATCH v4 1/2] spi: Add Renesas R-Car Gen3 RPC SPI controller
driver
Hello!
On 01/03/2019 09:35 AM, masonccyang@...c.com.tw wrote:
[...]
>> >> > +#define RPC_CMNCR_MOIIO3(val) (((val) & 0x3) << 22)
>> >> > +#define RPC_CMNCR_MOIIO2(val) (((val) & 0x3) << 20)
>> >> > +#define RPC_CMNCR_MOIIO1(val) (((val) & 0x3) << 18)
>> >> > +#define RPC_CMNCR_MOIIO0(val) (((val) & 0x3) << 16)
>> >> > +#define RPC_CMNCR_MOIIO_HIZ (RPC_CMNCR_MOIIO0(3) |
>> >> RPC_CMNCR_MOIIO1(3) | \
>> >> > + RPC_CMNCR_MOIIO2(3) | RPC_CMNCR_MOIIO3(3))
>> >> > +#define RPC_CMNCR_IO3FV(val) (((val) & 0x3) << 14)
>> >> > +#define RPC_CMNCR_IO2FV(val) (((val) & 0x3) << 12)
>> >>
>> >> Like I said, the above 2 aren't documented in the manual v1.00...
>> >
>> > okay, add a description as:
>> > /* RPC_CMNCR_IO3FV/IO2FV are undocumented bit, but must be set */
>> > #define RPC_CMNCR_IO3FV(val) (((val) & 0x3) << 14)
>> > #define RPC_CMNCR_IO2FV(val) (((val) & 0x3) << 12)
>> > #define RPC_CMNCR_IO0FV(val) (((val) & 0x3) << 8)
>> > #define RPC_CMNCR_IOFV_HIZ (RPC_CMNCR_IO0FV(3) | RPC_CMNCR_IO2FV(3) | \
>> > RPC_CMNCR_IO3FV(3))
>> >
>> > is it ok?
>>
>> Yes. But would have been enough if you just commented with // on
>> the same line --
>> it seems these are legal now...
>
> on the same line is over 80 char,
> #define RPC_CMNCR_IO3FV(val) (((val) & 0x3) << 14) // undocumented bit, but must be set
> #define RPC_CMNCR_IO2FV(val) (((val) & 0x3) << 12) // undocumented bit, but must be set
>
> or just
> #define RPC_CMNCR_IO3FV(val) (((val) & 0x3) << 14) // undocumented bit
> #define RPC_CMNCR_IO2FV(val) (((val) & 0x3) << 12) // undocumented bit
> is it ok ?
The second variant would be enough.
[...]
>> >> > + 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_write(rpc->regmap, RPC_CMNCR, RPC_CMNCR_SFDE |
>> >> > + RPC_CMNCR_MOIIO_HIZ | RPC_CMNCR_IOFV_HIZ |
>> >> > + RPC_CMNCR_BSZ(0));
>> >>
>> >> Why not set this in the probing time and only set/clear the MD bit?
>> >>
>> >
>> > same above!
>> > Make sure the value in these register are setting correctly
>> > before RPC starting a SPI transfer.
>>
>> You can set it once and only change the bits you need to change afterwards.
>> What's wrong with it?
>>
>
> if so, it will patch to:
> ------------------------------------------------------
> regmap_read(rpc->regmap, RPC_CMNCR, &data);
> data &= ~RPC_CMNCR_MD;
> regmap_write(rpc->regmap, RPC_CMNCR, data);
> ------------------------------------------------------
> Do you think this way is better ?
No, this one is better:
regmap_update_bits(rpc->regmap, RPC_CMNCR, RPC_CMNCR_MD, 0);
> maybe this is better,
> write(read(rpc->regs + RPC_CMNCR) & ~RPC_CMNCR_MD,
> rpc->regs + RPC_CMNCR);
It's effectively the same code as your 1st variant...
[...]
>> >> > +static void rpc_spi_transfer_setup(struct rpc_spi *rpc,
>> >> > + struct spi_message *msg)
>> >> > +{
>> >> [...]
>> >> > + for (i = xfercnt - 1; i < xfercnt && xfercnt > 1; i++) {
>> >> > + if (xfer[i].rx_buf) {
>> >> > + rpc->smenr |=
>> >> > + RPC_SMENR_SPIDE(rpc_bits_set(xfer[i].len)) |
>> >> > + RPC_SMENR_SPIDB
>> >> > + (ilog2((unsigned int)xfer[i].rx_nbits));
>> >>
>> >> Mhm, I would indent this contination line by 1 extra tab...
>> >>
>> >> > + } else if (xfer[i].tx_buf) {
>> >> > + rpc->smenr |=
>> >> > + RPC_SMENR_SPIDE(rpc_bits_set(xfer[i].len)) |
>> >> > + RPC_SMENR_SPIDB
>> >> > + (ilog2((unsigned int)xfer[i].tx_nbits));
>> >>
>> >> And this one...
>> >
>> > like this ?
>> > --------------------------------------------------------------------
>> > for (i = xfercnt - 1; i < xfercnt && xfercnt > 1; i++) {
>> > if (xfer[i].rx_buf) {
>> > rpc->smenr |=
>> > RPC_SMENR_SPIDE(rpc_bits_set(xfer
>> [i].len)) |
>> > RPC_SMENR_SPIDB(
>> > ilog2((unsigned int)xfer
>> [i].rx_nbits));
>> > } else if (xfer[i].tx_buf) {
>> > rpc->smenr |=
>> > RPC_SMENR_SPIDE(rpc_bits_set(xfer
>> [i].len)) |
>> > RPC_SMENR_SPIDB(
>> > ilog2((unsigned int)xfer
>> [i].tx_nbits));
>>
>> I didn't mean you need to leave ( on the first line, can be left
>> on the new
>> line, as before.
>>
>
> how about this style ?
> -------------------------------------------------------------------------------------
> for (i = xfercnt - 1; i < xfercnt && xfercnt > 1; i++) {
> if (xfer[i].rx_buf) {
> rpc->smenr |= RPC_SMENR_SPIDE(
> rpc_bits_set(xfer[i].len)) |
> RPC_SMENR_SPIDB(
> ilog2((unsigned int)xfer[i].rx_nbits));
> } else if (xfer[i].tx_buf) {
> rpc->smenr |= RPC_SMENR_SPIDE(
> rpc_bits_set(xfer[i].len)) |
> RPC_SMENR_SPIDB(
> ilog2((unsigned int)xfer[i].tx_nbits));
> }
> }
Looks even worse...
> ------------------------------------------------------------------------------------------
>
> best regards,
> Mason
[...]
MBR, Sergei
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