Re: [PATCH v2] riscv: Fix detecting FPU support in standard extension

[Yu-Chien Peter Lin]

On Sun, Nov 13, 2022 at 03:47:38PM -0600, Samuel Holland wrote:
> On 11/5/22 01:02, Yu Chien Peter Lin wrote:
> > We should check the string until it hits underscore, in case it
> > searches for the letters in the custom extension. For example,
> > "rv64imac_xandes" will be treated as D extension support since
> > there is a "d" in "andes", resulting illegal instruction caused
> > by initializing FCSR.
> > 
> > Signed-off-by: Yu Chien Peter Lin 
> > ---
> >  arch/riscv/cpu/cpu.c | 14 +++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
> > index 52ab02519f..d34c8efce0 100644
> > --- a/arch/riscv/cpu/cpu.c
> > +++ b/arch/riscv/cpu/cpu.c
> > @@ -36,6 +36,7 @@ static inline bool supports_extension(char ext)
> >  #ifdef CONFIG_CPU
> > struct udevice *dev;
> > char desc[32];
> > +   int i;
> >  
> > uclass_find_first_device(UCLASS_CPU, );
> > if (!dev) {
> > @@ -43,9 +44,16 @@ static inline bool supports_extension(char ext)
> > return false;
> > }
> > if (!cpu_get_desc(dev, desc, sizeof(desc))) {
> > -   /* skip the first 4 characters (rv32|rv64) */
> > -   if (strchr(desc + 4, ext))
> > -   return true;
> > +   /*
> > +* skip the first 4 characters (rv32|rv64) and
> > +* check until underscore
> > +*/
> 
> This probably works for the intended usage, but it is not guaranteed to
> work. Underscores are allowed even between single-letter extensions. See
> section 29.5 ("Underscores") of the unprivileged spec. Still, this is an
> improvement, so:
> 
> Reviewed-by: Samuel Holland 

Aah, I missed that case.
I supposed the strings always match the pattern stated in riscv cpus
binding [1], the detection logic here needs to be updated once the
case is also allowed.

[1] 
https://github.com/torvalds/linux/blob/v6.1-rc5/Documentation/devicetree/bindings/riscv/cpus.yaml#L83

Thanks for your review!

Best regards,
Peter Lin

> 
> > +   for (i = 4; i < sizeof(desc); i++) {
> > +   if (desc[i] == '_' || desc[i] == '\0')
> > +   break;
> > +   if (desc[i] == ext)
> > +   return true;
> > +   }
> > }
> >  
> > return false;
> 

Re: [PATCH v2] riscv: Fix detecting FPU support in standard extension

[Samuel Holland]

On 11/5/22 01:02, Yu Chien Peter Lin wrote:
> We should check the string until it hits underscore, in case it
> searches for the letters in the custom extension. For example,
> "rv64imac_xandes" will be treated as D extension support since
> there is a "d" in "andes", resulting illegal instruction caused
> by initializing FCSR.
> 
> Signed-off-by: Yu Chien Peter Lin 
> ---
>  arch/riscv/cpu/cpu.c | 14 +++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
> index 52ab02519f..d34c8efce0 100644
> --- a/arch/riscv/cpu/cpu.c
> +++ b/arch/riscv/cpu/cpu.c
> @@ -36,6 +36,7 @@ static inline bool supports_extension(char ext)
>  #ifdef CONFIG_CPU
>   struct udevice *dev;
>   char desc[32];
> + int i;
>  
>   uclass_find_first_device(UCLASS_CPU, );
>   if (!dev) {
> @@ -43,9 +44,16 @@ static inline bool supports_extension(char ext)
>   return false;
>   }
>   if (!cpu_get_desc(dev, desc, sizeof(desc))) {
> - /* skip the first 4 characters (rv32|rv64) */
> - if (strchr(desc + 4, ext))
> - return true;
> + /*
> +  * skip the first 4 characters (rv32|rv64) and
> +  * check until underscore
> +  */

This probably works for the intended usage, but it is not guaranteed to
work. Underscores are allowed even between single-letter extensions. See
section 29.5 ("Underscores") of the unprivileged spec. Still, this is an
improvement, so:

Reviewed-by: Samuel Holland 

> + for (i = 4; i < sizeof(desc); i++) {
> + if (desc[i] == '_' || desc[i] == '\0')
> + break;
> + if (desc[i] == ext)
> + return true;
> + }
>   }
>  
>   return false;

Re: [PATCH v2] riscv: Fix detecting FPU support in standard extension

[Padmarao.Begari]

> On Sat, 2022-11-05 at 14:02 +0800, Yu Chien Peter Lin wrote:
> 
> We should check the string until it hits underscore, in case it
> searches for the letters in the custom extension. For example,
> "rv64imac_xandes" will be treated as D extension support since
> there is a "d" in "andes", resulting illegal instruction caused
> by initializing FCSR.
> 
> Signed-off-by: Yu Chien Peter Lin 
> ---
>  arch/riscv/cpu/cpu.c | 14 +++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
> index 52ab02519f..d34c8efce0 100644
> --- a/arch/riscv/cpu/cpu.c
> +++ b/arch/riscv/cpu/cpu.c
> @@ -36,6 +36,7 @@ static inline bool supports_extension(char ext)
>  #ifdef CONFIG_CPU
> struct udevice *dev;
> char desc[32];
> +   int i;
> 
> uclass_find_first_device(UCLASS_CPU, );
> if (!dev) {
> @@ -43,9 +44,16 @@ static inline bool supports_extension(char ext)
> return false;
> }
> if (!cpu_get_desc(dev, desc, sizeof(desc))) {
> -   /* skip the first 4 characters (rv32|rv64) */
> -   if (strchr(desc + 4, ext))
> -   return true;
> +   /*
> +* skip the first 4 characters (rv32|rv64) and
> +* check until underscore
> +*/
> +   for (i = 4; i < sizeof(desc); i++) {
> +   if (desc[i] == '_' || desc[i] == '\0')
> +   break;
> +   if (desc[i] == ext)
> +   return true;
> +   }
> 

Reviewed-by: Padmarao Begari 

> }
> 
> return false;
> --
> 2.34.1
> 

Re: [PATCH v2] riscv: Fix detecting FPU support in standard extension

[Rick Chen]

> From: U-Boot  On Behalf Of Yu Chien Peter Lin
> Sent: Saturday, November 05, 2022 2:02 PM
> To: u-boot@lists.denx.de
> Cc: sam...@sholland.org; Peter Yu-Chien Lin(林宇謙) 
> Subject: [PATCH v2] riscv: Fix detecting FPU support in standard extension
>
> We should check the string until it hits underscore, in case it searches for 
> the letters in the custom extension. For example, "rv64imac_xandes" will be 
> treated as D extension support since there is a "d" in "andes", resulting 
> illegal instruction caused by initializing FCSR.
>
> Signed-off-by: Yu Chien Peter Lin 
> ---
>  arch/riscv/cpu/cpu.c | 14 +++---
>  1 file changed, 11 insertions(+), 3 deletions(-)

Reviewed-by: Rick Chen 

[PATCH v2] riscv: Fix detecting FPU support in standard extension

[Yu Chien Peter Lin]

We should check the string until it hits underscore, in case it
searches for the letters in the custom extension. For example,
"rv64imac_xandes" will be treated as D extension support since
there is a "d" in "andes", resulting illegal instruction caused
by initializing FCSR.

Signed-off-by: Yu Chien Peter Lin 
---
 arch/riscv/cpu/cpu.c | 14 +++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
index 52ab02519f..d34c8efce0 100644
--- a/arch/riscv/cpu/cpu.c
+++ b/arch/riscv/cpu/cpu.c
@@ -36,6 +36,7 @@ static inline bool supports_extension(char ext)
 #ifdef CONFIG_CPU
struct udevice *dev;
char desc[32];
+   int i;
 
uclass_find_first_device(UCLASS_CPU, );
if (!dev) {
@@ -43,9 +44,16 @@ static inline bool supports_extension(char ext)
return false;
}
if (!cpu_get_desc(dev, desc, sizeof(desc))) {
-   /* skip the first 4 characters (rv32|rv64) */
-   if (strchr(desc + 4, ext))
-   return true;
+   /*
+* skip the first 4 characters (rv32|rv64) and
+* check until underscore
+*/
+   for (i = 4; i < sizeof(desc); i++) {
+   if (desc[i] == '_' || desc[i] == '\0')
+   break;
+   if (desc[i] == ext)
+   return true;
+   }
}
 
return false;
-- 
2.34.1