[U-Boot] [UBOOT PATCH v3 3/3] spi: xilinx_spi: Added support to read JEDEC-id twice at the boot time

[Jagan Teki]

On Mon, Jun 25, 2018 at 4:06 PM, Vipul Kumar <vipulk at xilinx.com> wrote:
> Hi Jagan,
>
>> -----Original Message-----
>> From: Jagan Teki [mailto:jagannadh.teki at gmail.com]
>> Sent: Monday, June 25, 2018 3:47 PM
>> To: Vipul Kumar <vipulk at xilinx.com>
>> Cc: U-Boot Mailing List <u-boot at lists.denx.de>; Michal Simek
>> <michals at xilinx.com>
>> Subject: Re: [U-Boot] [UBOOT PATCH v3 3/3] spi: xilinx_spi: Added support to
>> read JEDEC-id twice at the boot time
>>
>> On Thu, Jun 21, 2018 at 2:53 PM, Vipul Kumar <vipul.kumar at xilinx.com>
>> wrote:
>> > This patch is for the startup block issue in the spi controller.
>> > SPI clock is passing through STARTUP block to FLASH. STARTUP block
>> > don't provide clock as soon as QSPI provides command. So, first
>> > command fails.
>>
>> Does this a controller issue?
>
> Yes, this is a controller issue.
>
>>
>> >
>> > This patch added support to read JEDEC id in xilinx_spi_xfer ().
>> >
>> > Signed-off-by: Vipul Kumar <vipul.kumar at xilinx.com>
>> > ---
>> > Changes in v3:
>> > - No change
>> > ---
>> >  drivers/spi/xilinx_spi.c | 41
>> > +++++++++++++++++++++++++++++++++++++++++
>> >  1 file changed, 41 insertions(+)
>> >
>> > diff --git a/drivers/spi/xilinx_spi.c b/drivers/spi/xilinx_spi.c index
>> > 4026540..61301c2 100644
>> > --- a/drivers/spi/xilinx_spi.c
>> > +++ b/drivers/spi/xilinx_spi.c
>> > @@ -204,6 +204,40 @@ static u32 xilinx_spi_read_rxfifo(struct udevice
>> *bus, u8 *rxp, u32 rxbytes)
>> >         return i;
>> >  }
>> >
>> > +static void xilinx_startup_block(struct udevice *dev, unsigned int bytes,
>> > +                                const void *dout, void *din) {
>> > +       struct udevice *bus = dev_get_parent(dev);
>> > +       struct xilinx_spi_priv *priv = dev_get_priv(bus);
>> > +       struct xilinx_spi_regs *regs = priv->regs;
>> > +       struct dm_spi_slave_platdata *slave_plat =
>> dev_get_parent_platdata(dev);
>> > +       const unsigned char *txp = dout;
>> > +       unsigned char *rxp = din;
>> > +       static int startup;
>> > +       u32 reg, count;
>> > +       u32 txbytes = bytes;
>> > +       u32 rxbytes = bytes;
>> > +
>> > +       /*
>> > +        * This loop runs two times. First time to send the command.
>> > +        * Second time to transfer data. After transferring data,
>> > +        * it sets txp to the initial value for the normal operation.
>> > +        */
>> > +       for ( ; startup < 2; startup++) {
>> > +               count = xilinx_spi_fill_txfifo(bus, txp, txbytes);
>> > +               reg = readl(&regs->spicr) & ~SPICR_MASTER_INHIBIT;
>> > +               writel(reg, &regs->spicr);
>> > +               count = xilinx_spi_read_rxfifo(bus, rxp, rxbytes);
>> > +               txp = din;
>> > +
>> > +               if (startup) {
>> > +                       spi_cs_deactivate(dev);
>> > +                       spi_cs_activate(dev, slave_plat->cs);
>> > +                       txp = dout;
>> > +               }
>> > +       }
>> > +}
>> > +
>> >  static int xilinx_spi_xfer(struct udevice *dev, unsigned int bitlen,
>> >                             const void *dout, void *din, unsigned long
>> > flags)  { @@ -236,6 +270,13 @@ static int xilinx_spi_xfer(struct
>> > udevice *dev, unsigned int bitlen,
>> >         if (flags & SPI_XFER_BEGIN)
>> >                 spi_cs_activate(dev, slave_plat->cs);
>> >
>> > +       /*
>> > +        * This is the work around for the startup block issue in
>> > +        * the spi controller. SPI clock is passing through STARTUP
>> > +        * block to FLASH. STARTUP block don't provide clock as soon
>> > +        * as QSPI provides command. So first command fails.
>> > +        */
>> > +       xilinx_startup_block(dev, bytes, dout, din);
>>
>> But not every spi_xfer from flash side is to read JEDEC ID? during probe of sf,
>> the relevant spi_xfer is to read JEDEC ID
>
> Inside xilinx_startup_block() function, we are using static variable, so that code will execute only first time.

Sorry, IMHO mainline won't accept this kind of hack (particularly
avoiding function execution through static variables) by for the sake
of bug fix. Having a proper condition to check and fix the errata look
fine to me, any idea how Linux handling this?