Hi Prabhakar,
On Wed, 18 Jun 2025 at 14:06, Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> On Wed, Jun 18, 2025 at 8:03 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > On Tue, 17 Jun 2025 at 23:05, Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> > > On Mon, Mar 31, 2025 at 7:25 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > > > On Mon, 31 Mar 2025 at 17:33, Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> > > > > > From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > > > > > On Mon, 31 Mar 2025 at 16:34, Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> > > > > > > > From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> On Mon, 31 Mar 2025
> > > > > > > > at 15:54, Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> > > > > > > > > > From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx> Document support for
> > > > > > > > > > the Expanded Serial Peripheral Interface (xSPI) Controller in
> > > > > > > > > > the Renesas RZ/G3E
> > > > > > > > > > (R9A09G047) SoC.
> > > > > > > > > >
> > > > > > > > > > Reviewed-by: Rob Herring (Arm) <robh@xxxxxxxxxx>
> > > > > > > > > > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > > > > > > >
> > > > > > > > > > --- /dev/null
> > > > > > > > > > +++ b/Documentation/devicetree/bindings/memory-controllers/renes
> > > > > > > > > > +++ as,r
> > > > > > > > > > +++ zg3e
> > > > > > > > > > +++ -xspi.yaml
> > > > > > > >
> > > > > > > > > > + spi@11030000 {
> > > > > > > > > > + compatible = "renesas,r9a09g047-xspi";
> > > > > > > > > > + reg = <0x11030000 0x10000>, <0x20000000 0x10000000>;
> > > > > > > > > > + reg-names = "regs", "dirmap";
> > > > > > > > > > + interrupts = <GIC_SPI 228 IRQ_TYPE_EDGE_RISING>,
> > > > > > > > > > + <GIC_SPI 229 IRQ_TYPE_EDGE_RISING>;
> > > > > > > > > > + interrupt-names = "pulse", "err_pulse";
> > > > > > > > > > + clocks = <&cpg CPG_MOD 0x9f>, <&cpg CPG_MOD 0xa0>,
> > > > > > > > > > + <&cpg CPG_MOD 0xa1>, <&cpg CPG_MOD 0xa1>;
> > > > > > > > >
> > > > > > > > > On the next version I am going to update spix2 clk as <&cpg
> > > > > > > > > CPG_CORE R9A09G047_SPI_CLK_SPIX2>
> > > >
> > > > According to the RZ/G3E clock system diagram, (the parent of) clk_spi
> > > > is derived from (the parent of) clk_spix2, not the other way around?
> > > > So you can model clk_spi as a fixed divider clock with parent clk_spix2
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[A]
> > > > and factor two. I.e. provide a new core clock R9A09G047_SPI_CLK_SPI
> > > > instead of your proposed R9A09G047_SPI_CLK_SPIX2?
> > > >
> > > With this approach when R9A09G047_SPI_CLK_SPI is used as a core clock
> > > and XSPI node is disabled the clk_summary reports the core clock is ON
> > > (while it's actually OFF).
> >
> > Is that a real problem, or is it purely cosmetic?
> Just cosmetic tbh as despite being a MOD clock we have to define it as
> a core clock in the DT.
>
> > > Can we maybe use a unused ON index and ON bit for example 25, 0 (ie
> > > 0x190) and represent this is a module clock for example for the
> > > spi_clk_spix2 clock and use this in the DT and let the CPG core code
> > > handle such turning ON/OF the module clocks based on the enable count
> > > which will be handled internally in the driver?
> >
> > Please do not use "unused" module clock bits. These do not describe
> > the hardware, and may actually exist in the hardware (try disabling
> > all undocumented module clocks, and observe what fails...).
> >
> Agreed, "unused" module clock bits were only used as a dummy. The
> read/write operations were only performed on the actual bits which are
> documented in the HW manual.
>
> > If spi_clk_spi really must show being disabled, you can change it
> > from a fixed divider clock (which does not implement .{en,dis}able())
> > to a custom fixed divider clock that does implement .{en,dis}able()
> > and keeps track internally of the fake state, or even looks at the
> > state of spi_clk_spix2?
> >
> Good point. Maybe instead of implementing the dummy .{en,dis}able() I
> will implement the is_enabled() + (clk_fixed_factor_ops). The
> is_enabled() will take care of reading from the MON bits and report
> the actual state of the clock.
>
> > However, upon second look, spi_clk_spi is not implemented as a fixed
> > divider clock with parent clk_spix2, as described above:
> >
> > .smux2_xspi_clk1 0 0 0 320000000 0 0 50000 Y
> > .pllcm33_xspi 0 0 0 40000000 0 0 50000 Y
> > spi_clk_spix2 0 0 0 40000000 0 0 50000 N
> > spi_clk_spi 0 0 0 20000000 0 0 50000 Y
> > spi_aclk 0 0 0 200000000 0 0 50000 N
> > spi_hclk 0 0 0 200000000 0 0 50000 N
> > .smux2_xspi_clk0 0 0 0 533333333 0 0 50000 Y
> >
> > Instead, they both use pllcm33_xspi as the parent clock.
> > Apparently I missed that in the review of RZ/G3E XSPI clock support.
> > The changelog for that patch does describe the correct topology?
> >
> The topology is correct for RZ/G3E, spi/spix2 are sourced from
> pllcm33_xspi divider and there is a divider (/2) for spi.
Both spi_clk_spix2 and spi_clk_spix have .pllcm33_xspi as
immediate parent.
[A] describes something different:
.pllcm33_xspi 0 0 0 40000000 0 0 50000 Y
spi_clk_spix2 0 0 0 40000000 0 0 50000 N
spi_clk_spi 0 0 0 20000000 0 0 50000 Y
I.e. if spi_clk_spix2() is disabled, spi_clk_spi() is disabled, too.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
