[U-Boot] [PATCH v3 1/2] spi: zynqmp_gqspi: Add support for ZynqMP qspi driver

[Jagan Teki]

On Wed, May 9, 2018 at 1:20 PM, Siva Durga Prasad Paladugu
<sivadur at xilinx.com> wrote:
>
> Hi,
>
>> -----Original Message-----
>> From: Jagan Teki [mailto:jagannadh.teki at gmail.com]
>> Sent: Wednesday, May 09, 2018 1:12 PM
>> To: Siva Durga Prasad Paladugu <sivadur at xilinx.com>
>> Cc: Jagan Teki <jagan at amarulasolutions.com>; U-Boot-Denx <u-
>> boot at lists.denx.de>; michal.simek at xilinx.com
>> Subject: Re: [U-Boot] [PATCH v3 1/2] spi: zynqmp_gqspi: Add support for
>> ZynqMP qspi driver
>>
>> On Wed, May 9, 2018 at 12:33 PM, Siva Durga Prasad Paladugu
>> <sivadur at xilinx.com> wrote:
>> > Hi Jagan,
>> >
>> >> -----Original Message-----
>> >> From: Jagan Teki [mailto:jagan at amarulasolutions.com]
>> >> Sent: Wednesday, May 09, 2018 12:01 PM
>> >> To: Siva Durga Prasad Paladugu <sivadur at xilinx.com>
>> >> Cc: U-Boot-Denx <u-boot at lists.denx.de>; michal.simek at xilinx.com
>> >> Subject: Re: [PATCH v3 1/2] spi: zynqmp_gqspi: Add support for
>> ZynqMP
>> >> qspi driver
>> >>
>> >> On Tue, May 8, 2018 at 3:43 PM, Siva Durga Prasad Paladugu
>> >> <siva.durga.paladugu at xilinx.com> wrote:
>> >> > This patch adds qspi driver support for ZynqMP SoC. This driver is
>> >> > responsible for communicating with qspi flash devices.
>> >> >
>> >> > Signed-off-by: Siva Durga Prasad Paladugu
>> >> > <siva.durga.paladugu at xilinx.com>
>> >> > ---
>> >> > Changes for v3:
>> >> > - Renamed all macros, functions, files and configs as per comment
>> >> > - Used wait_for_bit wherever required
>> >> > - Removed unnecessary header inclusion
>> >> >
>> >> > Changes for v2:
>> >> > - Rebased on top of latest master
>> >> > - Moved macro definitions to .h file as per comment
>> >> > - Fixed magic values with macros as per comment
>> >> > ---
>> >> >  arch/arm/include/asm/arch-zynqmp/zynqmp_gqspi.h | 154 ++++++
>> >> >  drivers/spi/Kconfig                             |   7 +
>> >> >  drivers/spi/Makefile                            |   1 +
>> >> >  drivers/spi/zynqmp_gqspi.c                      | 670
>> >> ++++++++++++++++++++++++
>> >> >  4 files changed, 832 insertions(+)  create mode 100644
>> >> > arch/arm/include/asm/arch-
>> >> zynqmp/zynqmp_gqspi.h
>> >> >  create mode 100644 drivers/spi/zynqmp_gqspi.c
>> >> >
>> >> > diff --git a/arch/arm/include/asm/arch-zynqmp/zynqmp_gqspi.h
>> >> > b/arch/arm/include/asm/arch-zynqmp/zynqmp_gqspi.h
>> >>
>> >> already asked you to move this header code in driver .c file
>> >
>> > You might have missed my reply to your earlier comment on this. These
>> > were moved to .h based on comment from Lukasz in v1.
>> > I don’t have any issue in having them anywhere. Let me know your choice.
>>
>> I'm trying to align Linux code, better to move like that and make sure to use
>> similar macros.
>>
>> >
>
> [snip]
>
>> >> > +static void zynqmp_qspi_genfifo_cmd(struct zynqmp_qspi_priv
>> *priv) {
>> >> > +       u8 command = 1;
>> >> > +       u32 gen_fifo_cmd;
>> >> > +       u32 bytecount = 0;
>> >> > +
>> >> > +       while (priv->len) {
>> >> > +               gen_fifo_cmd = zynqmp_qspi_bus_select(priv);
>> >> > +               gen_fifo_cmd |= GQSPI_GFIFO_TX;
>> >> > +
>> >> > +               if (command) {
>> >> > +                       command = 0;
>> >> > +                       last_cmd = *(u8 *)priv->tx_buf;
>> >> > +               }
>> >>
>> >> don't understand this code can you explain? command assigned 1 it
>> >> will not updated anywhere?
>> >
>> > I want to store last command sent. As the first byte in loop only
>> > contains command, it ensures it fills only for one time and next time it
>> may contain data to be sent along with command.
>> > Command initialized to 1 while declaring it above(u8 command = 1).
>>
>> Ok the first TX buf has command and reused in tx and rx fifo, how come to
>> use use same in rx fifo? why is is last_cmd it is first_cmd?
>
> This holds the command that was sent last to the device before we use in tx/rx fill, hence used this name.

ie. what I wonder, usually the spi transfer start with cmd + data in
that case it would be the first command, did gqspi work reverse way?

Jagan.